Linear Technology DC1937B Quick setup guide

1
dc1937bf
DEMO MANUAL DC1937B
DESCRIPTION
LTC3350EUHF
High Current Supercapacitor Backup
Controller and System Monitor
Demonstration circuit 1937B is a supercapacitor charger
and backup controller with supercapacitor health and
system monitoring; featuring the LT C
®
3350. The LTC3350
hasabucksupercapacitor charger, backup boost controller
and an input ideal diode to disconnect the input supply
in backup mode. An output ideal diode allows the super-
capacitors to supply the output when VCAP is above the
set backup voltage. As the capacitor stack voltage drops
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
QuikEval is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners.
PERFORMANCE SUMMARY
down to the set output voltage, the LTC3350 will operate
as a boost regulator to supply the output until the energy
in the supercapacitors are depleted.
Design files for this circuit board are available at
http://www.linear.com/demo/DC1937B
Specifications are at TA= 25°C
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Supply Range 10.8 12 20 V
Input Current Limit 2 A
VOUT Backup Operating Voltage Boost Mode 6 V
VCAP Float Voltage Buck Mode 10 V
Max Charge Current 5.33 A
tBACKUP PBACKUP = 25W, IBOOST = 9.67A, 3 ≤ VCAP ≤ 10 3.2 s
BOARD PHOTO

2
dc1937bf
DEMO MANUAL DC1937B
QUICK START PROCEDURE
ObtainandconnectaDC590BboardtotheDC1937Bboard.
Using short twisted pair leads for the power connections
and with the LOAD and the power supply OFF. Refer to
Figure 1 and Figure 2 for the proper measurement and
equipment setup. Follow the procedure below.
1. Refer to the DC590B Quick Start Guide for QuikEval™
setup and software installation details.
2. Make sure the USB cable is connected between the
computer and the DC590B controller board.
3. Connect a 14-pin ribbon cable from the DC590B board
to the DC1937B board.
4. Set the VCCIO jumper, JP6, on the DC590B board to
the 5V position.
5. Set the JP1 jumper on the DC1937B board to the
DC590 position.
6. Start the Linear Technology QuikEval program. This
program should automatically detect the presence of
the LTC3350 demo board (DC1937B) and activate the
appropriate GUI, as seen in Figure 5.
TYPICAL APPLICATION
High Current Supercapacitor Charger and Backup Supply
Backup Operation
V
IN
PFI OUTFB
OUTFET
TGATE
SW
BGATE
ICAP
VCAP
CAP4
CAP3
CAP2
CAP1
CAPRTN
CAPFB
INFET VOUTSP VOUTSN
I
CHG
(STEP-DOWN) I
BACKUP
VCAP < VOUT
(STEP-UP)
VCAP > V
OUT
(DIRECT
CONNECT)
V
OUT
LTC3350
10F
VCAP
10F
10F
10F
dc1937b TA01a
I2C
VIN
2V/DIV
VCAP
2V/DIV
VOUT
2V/DIV
400ms/DIV
BACK PAGE APPLICATION CIRCUIT
0V
dc1937b TA01b
PBACKUP = 25W
VOUT
VCAP
VIN
7. With power off, connect a 0V to 20V, 25W supply
between the VIN and GND terminals with a series
ammeter and a voltmeter as shown in Figure 1.
8. Turn on and set the VIN input power supply to 12V and
observe the CAP voltages, input and charge current
on the GUI.
NOTE. Make sure that the input voltage does not
exceed 20V.
NOTE. The LTC3350 is intended to operate with a low
impedance source. If operating near the PFI rising
threshold, make sure the input voltage does not drop
more than 30mV • (R5 + R6)/R6, 266mV, during a
charge event.
9. On the LTC3350 Control Window, click on the CAP
and ESR Measurement START button. An In Process
indicator displays whilethe measurement is in process.
NOTE. Supercapacitors initially have large leakage
currents which causes the capacitance measurement
to be low. The capacitor measurements will be more
accurate after the 10F capacitors have been continu-
ously charged for more than 30 minutes.

3
dc1937bf
DEMO MANUAL DC1937B
10. Connecta0Wto25Wconstantpowerloadboxbetween
VOUT and GND and set to 25W.
11. Connect an oscilloscope probe each to VIN, VOUT,
VCAP and PFO. Set the oscilloscope to trigger on the
falling edge of PFO.
12. Remove the input power and observe how the output
drops to the regulation point and is maintained until
the energy in the supercapacitors are exhausted.
QUICK START PROCEDURE
13. The LTC3350 has the ability to monitor and report on
the supercapacitor and system voltages, currents, die
temperature and capacitor health. See the software
section and data sheet for more information.
14. The DC1937B can be modified to operate at differ-
ent frequencies, operating voltages, input and boost
currents. The Hardware Config tab allows the user to
enter the appropriate changes so the GUI can report
the correct measurements. See the Software section
for more details.
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple

4
dc1937bf
DEMO MANUAL DC1937B
APPLICATION INFORMATION
Figure 3. Charger Efficiency Figure 4. Boost Efficiency
VCAP (V)
0
EFFICIENCY (%)
100
10
90
70
50
30
80
60
40
20
05 93 7
dc1937b F03
10
4 82 61
IOUT (A)
0
EFFICIENCY (%)
100
10
90
70
50
30
80
60
40
20
01.5 3.50.5 2.5
dc1937b F04
4.0
1.0 3.02.0
VCAP = 5V
VCAP = 4V
VCAP = 3V
The DC1937B was designed to provide 25W of power for
a total of 1.8 seconds with a backup voltage of 6V. It was
also determined that the maximum life expectancy of this
product is six years with a maximum ambient tempera-
ture of 45°C. When choosing the capacitance needed the
condition of the supercapacitor at end of life (EOL) needs
to be considered. EOL is typically when the capacitance
decreases by 30% and when the ESR doubles. With this
knowledge and a few calculations the capacitors needed
for this application can be chosen. Refer to the LTC3350
data sheet for more details on the formulas used in the
following examples.
Since the backup time and backup power are known, the
next item that needs to be determined is the maximum
voltage to be applied to the capacitor VCELL(MAX) to provide
the maximum life expectancy for the application. Refer to
the capacitor manufacture’s data sheet for this informa-
tion. A VCELL(MAX) of 2.5V was chosen for the 6 year life
expectancy of this product.
The number of capacitors in the stack also needs to be
chosen plus the Utilization Factor (αB). αBis the amount
of energy in the capacitor to be used for backup. A typi-
cal αBis 80%, but a conservative αBof 70% was used
on the DC1937B. The minimum capacitance required for
each capacitor in the stack at EOL can be calculated by
the following equation:
CEOL ≥
4P
BACKUP
• t
BACKUP
nηVCELL(MAX)2•
αB+ αB– 1– αB
( )
ln 1+ αB
1– αB














–
1
Where ηrepresents the boost efficiency, n represents the
number of capacitors in the stack. Based on an efficiency
of 90% and the backup requirements, the minimum CEOL
is calculated as:
CEOL ≥
4•25W •1.8s
4• 0.9 •(2.5V)2•
0.7+0.7 – 1– 0.7
( )
ln 1+0.7
1– 0.7














–1
=6.816F
The maximum capacitor ESR at end of life can then be
determined below:
ESREOL ≤η(1– αB)nV2(CELL(MAX)
4PBACKUP

5
dc1937bf
DEMO MANUAL DC1937B
The capacitor ESREOL is determined below:
ESREOL ≤0.9(1– 0.7)• 4 •(2.5V)2
4•25W
=67.5mΩ
Now the EOL parameters are known, the capacitor can be
chosenbasedon the manufacture’scapacitorspecification
for EOL. For the DC1937B, the NESSCAP ESHSR-0010C0-
002R7 was chosen with a CEOL of 7F, an ESREOL of 64mΩ
and a maximum current of 10.1A.
To verifythe capacitors are adequate at EOL we first need to
determine the minimum stack voltage (VSTK(MIN)) at EOL.
VSTK(MIN) will be limited by either the maximum power
transfer rule or by current limit, whichever is greater. The
minimum capacitor voltage due to the maximum power
transfer rule can be calculated with the following formula:
VSTK(MIN) =4•ESREOL •n•PBACKUP
η
VSTK(MIN) is the maximum stack voltage (n• VCELL). The
desired VSTK(MIN) due to the maximum power transfer
rule is calculated as:
4• 4 •64mΩ•25W
0.9 =5.333V
VSTK(MIN) can also be determined by the current limit and
the ESREOL as shown in the following equation:
VSTK(MIN) =
P
BACKUP
ηI
LMAX
+nESREOLILMAX
Where ILMAX is the boost peak current limit. The EOL
VSTK(MIN) based on boost peak current limit is calculated
below:
25W
0.9 •9.67A
+4•64mΩ•9.67A =5.348V
Now VSTK(MIN) at EOL is known, the VSTK(MIN) can be
rearranged to calculate actual αBat EOL. The calculated
VSTK(MIN) can also be used to determine if the chosen
capacitor will be sufficient for worst case EOL conditions,
when both ESREOL and CEOL have been reached.
tBACKUP =
ηC
STK
4P
BACKUP
•
γ(MAX)V2(STK(MAX) –γ(MIN)V2(STK(MIN) – V2LOSS

 
Where CSTK is the total stack capacitance, VSTK(MIN) is
based on the higher calculated VSTK(MIN),
γ(MAX) =1+1– 4nESREOL •PBACKUP
ηV2STK(MAX)
,
γ(MIN) =1+1– 4nESREOL •PBACKUP
V2STK(MIN)
and
V2LOSS =4nESREOLP
BACKUP
ηln γ(MAX)VSTK(MAX) γ(MIN)VSTK(MIN)






The worst case EOL backup time is calculated below:
γ(MAX) =1+1– 4 • 4• 64mΩ•25W
0.9 •(10V)2=1.8459
γ(MIN) =1+1– 4• 4 •64mΩ•25W
0.9 •(5.348V)2=1.0740
VLOSS2=
4• 4 •64mΩ•25W
0.9 •
ln 1.8459 •10V
1.0740 •5.348V




=33.207V2
tBACKUP =
0.9 •
7
4




F
4•25W •
1.846 •(10V)2–1.074•(5.348V)2– 33.207V2

 =1.9s
The above results show that if both ESREOL and CEOL are
reached then the backup requirement will be met. If the
backup requirement was not met, then a capacitor with
lower ESR and/or more capacitance should be chosen.
APPLICATION INFORMATION

6
dc1937bf
DEMO MANUAL DC1937B
USING THE LTC3350 SOFTWARE
The LTC3350 program provides the ability to measure
and monitor the system voltages and currents plus the
health of the supercapacitors. It also allows the user to
set up alarms to report on specific events such as power
fail or cap measurement done. Refer to Figure 5 for an
illustration of the LTC3350 control window.
VIEW LTC3350 PRODUCT PAGE button opens an Internet
browser and searches the Linear Technology Corporation
website for information on the LTC3350 when an Internet
connection is available.
CAP and ESR Measurement START button starts a ca-
pacitor and ESR measurement. An indicator below the
START button indicates the status of the capacitor/ESR
measurement. The different states are; In Process, Done,
Pending or Failed.
Number of Caps Selected text box indicates the number
of capacitors selected using the CAP_SLCTx pins.
SMBALERT Detected indicator indicates if an SMBALERT
has been detected or not.
Clear SMBUS ALERT button sends an SMBus alert re-
sponse address to clear the SMBALERT. Note, the condi-
tion that caused the SMBALERT must be cleared before
the SMBALERT signal can be cleared.
CAP text box indicates the latest measured capacitance in
Farads for large capacitors and mF for smaller capacitors.
This measurement is based on the CAP scale setting in the
control register plus the Current and Oscillator Resistor
Settings on the Hardware Config tab.
ESR text box indicates the latest measured ESR in mΩ.
VCAP text box indicates the latest VCAP voltage in Volts.
ICHRG text box indicates the latest measured charge/
boost current in amps. This measurement is based on the
RSNSC setting on the Hardware Config tab.
VCAPx text box indicates the latest measured capacitor
voltage in Volts for the corresponding VCAP.
VIN text box indicates the latest measured input voltage
in Volts.
IIN text box indicates the latest measured input current in
amps. This measurement is based on the RSNSI setting
on the Hardware Config tab.
VOUT textbox indicates the latest measured VOUT in Volts.
GPImon
text box indicates the latest measured GPI voltage
in Volts. An internal buffer can be enabled for measuring
high impedance inputs.
Die Temp text box displays the latest internally measured
die temperature in °C.
Register text boxes displays the associated register values
in hexadecimal format.
Read Values button causes the LTC3350 to read all of the
ADC measured values. This is useful when the LTC3350
GUI “Auto Update” is disabled.
Auto Update Enable/Disable button causes the LTC3350
to read all of the LTC3350 registers periodically and writes
to any register changed when enabled. The Read Values,
Read All, or Update All buttons can be used instead to
update the registers when in the disabled state.
Read All button causes the LTC3350 to read all of the
LTC3350 registers. This is useful when the LTC3350 GUI
Auto Update is disabled.
CHARGER CONTROL TAB
The Charger Control tab contains the indicators and con-
trols for the capacitor charger and monitor plus the GPI
buffer enable as shown in Figure 5.
ChargerStatusSTATUSBitsindicateswhentheassociated
chrg_status register bits are set. See the data sheet from
more information on these bits.
Charger Status Read text box displays the last read
chrg_status register value in hexadecimal format.
CAP ESR Period text box allows the user to set a period
in which the LTC3350 will perform a capacitance and
ESR measurement. The text box is formatted in hours,
minutes, and seconds. The LSB for the CAP ESR Period
register is 10 seconds.
CAP ESR Period Write text box displays the value that
will be or has been written to the cap_esr_period register
value in hexadecimal format.
CAP ESR Period Read text box displays the last value read
from the cap_esr_period register in hexadecimal format.

7
dc1937bf
DEMO MANUAL DC1937B
USING THE LTC3350 SOFTWARE
Figure 5. LTC3350 Control Window
VCAP FB text box allows the user to set the CAPFB refer-
ence voltage from 0.6375V to 1.2V in 37.5mV increments.
The value in the text box is rounded to the nearest mV. The
VCAP text box is also updated with the calculated value
of the CAPFB reverence voltage and the resistor network
entered on the Hardware Config tab.
VCAP FB Write text box displays the value that will be or has
beenwrittentothevcapfb_dacregisterinhexadecimalformat.
VCAP FB Read text box displays the last value read from
the vcapfb_dac register in hexadecimal format.
VCAP text box allows the user to set the VCAP float volt-
age within the limits of the CAPFB reference voltage and
the CAPFB resistor network on the Hardware Config tab.
The value in the text box is rounded to the nearest mV.
The VCAP FB text box is also updated with the calculated
value using the CAPFB resistor network entered on the
Hardware Config tab.
VSHUNT text box allows the user to set the shunt regulator
voltage up to 3.6V or disable the shunt regulator. The shunt
voltage will be reset to the default value of 2.7057 every
time INTVCC is restored. Set VSHUNT to 0V to disable the
shunt regulator.
VSHUNTWritetextboxdisplaysthe value that will be or has
been written to the vshunt register in hexadecimal format.
VSHUNT Read text box displays the last value read from
the vshunt register in hexadecimal format.
Stop CAP Measurement sets the ctl_stop_capesr bit in
the ctl_reg register. This will cause any CAP/ESR mea-
surement in process to stop. This bit will reset when the
measurement has ceased.
CAP SCALE button sets the cap scale from large scale,
default scale for larger capacitors, to small scale for
smaller capacitors. The resolution is increased by 100x
in small scale.
GPI BUFFER ENABLE button sets the ctl_gpi_buffer_en
bit when enabling the GPI input buffer. When the GPI
BUFFER ENABLE is off then the GPI input is measured
without the input buffer.
Control Reg Write text box displays the value that will be
or has been written to the ctl_reg register in hexadecimal
format.
Control Reg Read text box displays the last value read
from the ctl_reg register in hexadecimal format.

8
dc1937bf
DEMO MANUAL DC1937B
Figure 6. Monitor Status/Alarms Tab
MONITOR STATUS/ALARMS TAB
The Monitor Status/Alarms tab contains the indicators for
the mon_status and alarm_reg bits plus control buttons
for the Monitor Status Mask, Alarm Mask and Alarm Clear
bits as shown in Figure 6.
Monitor Status STATUS Bits indicate when the associated
mon_status register bits are set. See the data sheet from
more information on these bits.
Monitor Status Read text box displays the last read
mon_status register value in hexadecimal format.
Mask Monitor Status buttons will allow the rising edge of
the associated monitor status bit to trigger the SMBALERT
when the mask bit is set to 1.
Mask Mointor Write text box displays the value that will
be or has been written to the msk_mon_status register
in hexadecimal format.
Mask Monitor Read text box displays the last read
msk_mon_status register value in hexadecimal format.
Alarm Bits indicatewhen the associated alarm_regregister
bits are set. See the data sheet from more information on
these bits.
Alarm Read text box displays the last read alarm_reg
register value in hexadecimal format.
Mask Alarm buttons will allow the associated alarm bit
to trigger the SMBALERT when the mask bit is set to 1.
Mask Alarm Write text box displays the value that will
be or has been written to the msk_alarms register in
hexadecimal format.
Mask Alarm Read text box displays the last read msk_
alarms register value in hexadecimal format.
Clear Alarm buttons will cause the associated alarm to
clear when the alarm condition no longer exists. The Clear
alarm bit will reset low when the alarm is cleared.
Clear Alarm Write text box displays the value that will
be or has been written to the msk_alarms register in
hexadecimal format.
Clear Alarm Read text box displays the last read msk_
alarms register value in hexadecimal format.
USING THE LTC3350 SOFTWARE

9
dc1937bf
DEMO MANUAL DC1937B
SET ALARMS TAB
The Set Alarms tab contains text boxes to allow the user
to set specific levels for each alarm register as shown in
Figure 7. Each alarm has an associated Write text box to
display the value that will be or has been written to the
associatedregister in hexadecimal format. Each alarm also
hasanassociatedReadtext box which displays the last read
contents of the associated register in hexadecimal format.
VIN/VOUT/VCAP/CAP/GPI UV alarm text boxes allow the
user to enter a voltage that will trigger an alarm when the
associated voltage drops below the entered voltage value
and the associated alarm mask bit is set.
VIN/VOUT/VCAP/CAP/GPI OV alarm text boxes allow the
user to enter a voltage that will trigger an alarm when the
associated voltage rises above the entered voltage value
and the associated alarm mask bit is set.
IIN OC alarm text boxes allow the user to enter a current
or the voltage across the sense resistor that will trigger an
alarm when the input current increase above the entered
value and the msk_iin_oc alarm mask bit is set.
USING THE LTC3350 SOFTWARE
Figure 7. Set Alarms Tab
CAPLOalarm text box allows the user to enteracapacitance
based on the current ctl_cap_scale setting in the ctl_reg. A
CAP LO alarm will be triggeredif the measured capacitance
islower than the enteredvalueandthe msk_cap_lobit is set.
ESR HI alarm text box allows the user to enter an ESR
value based on the RSNSC resistor value entered in the
Hardware Config tab. An ESR HI alarm will be triggered
if the measured ESR is higher than the entered value and
the msk_esr_hi bit is set.
ICHRG UC alarm text boxes allow the user to enter acurrent
or the voltage across the sense resistor that will trigger
an alarm when the charge current decreases below the
entered value and the msk_ichrg_lo bit is set.
Die Temp Cold alarm text box allows the user to enter a
die temperature in °C that will trigger an alarm when the
temperature decreases below the entered value and the
msk_dtemp_cold bit is set.
Die Temp Hot alarm text box allows the user to enter a
die temperature in °C that will trigger an alarm when the
temperature increases above the entered value and the
msk_dtemp_hot bit is set.

10
dc1937bf
DEMO MANUAL DC1937B
Figure 8. Hardware Config Tab
Apply button writes to all of the alarm registers and reads
the values back from the LTC3350.
Cancel button changes all the entered values that have
not yet been written to the LTC3350 back to their previ-
ous values.
Restore Defaults button changes all of the LTC3350 alarm
registers back to the default values determined from the
GUI. This does not set the alarm to the LTC3350’s default
settings of 0x0000.
HARDWARE CONFIG TAB
The Hardware Config tab, shown in Figure 8, contains text
boxes to allow the user to enter the values to configure
the necessary resistors to match the configuration of the
demo board. These values are used by the GUI to calculate
measured CAP and ESR values, display input/charge cur-
rents and max VCAP voltage for a given reference setting,
and also used in the Set Alarm tab text boxes.
VPFI Resistor Settings text boxes allow the user to enter
thePFIresistordivider network in kΩ.Thecalculated falling
PFI threshold set point is displayed in Volts.
VOUT Resistor Settings text boxes allow the user to enter
the VOUT resistor divider network in kΩ. The calculated
VOUT backup set point is displayed in Volts.
RITST text box allows the user to enter the RITST resistor
in Ω. The calculated test current setting is displayed in mA.
REXT text box allows the user to enter the external load
resistance, R28 and R29, added in Ω if any. Enter –1 if
thereis not any external loading and OPEN will be displayed
in the text box. See the Using Large Capacitor section for
more details.
RT text box allows the user to enter the RT resistor in kΩ.
The calculated oscillator setting is displayed in kHz.
Total RBalance text box allows the user to enter the
equivalent total balance resistance in Ω if any for ca-
pacitancestacks or packs that have external balancing.
Enter–1 if there is not any external balancing and OPEN
will be displayed in the text box.
RSNSI text box allows the user to enter the RSNSI resis-
tor in mΩ. The calculated input current limit setting is
displayed in Amps.
RSNSCtextboxallowstheusertoentertheRSNSCresistor
in mΩ. The calculated maximum charge current setting
is displayed in Amps.
VCAP Resistor Settings text boxes allow the user to enter
the CAPFB resistor divider network in kΩ. The calculated
maximum VCAP set point is displayed in Volts.
CAP1 Voltage Divider text boxes allow the user to enter
the CAP1 resistor divider network in kΩ if used. This is
primarily used for the Zeta/SEPIC application (Data sheet
Application Circuit 6). The displayed CAP1 voltage is
calculated from the maximum VCAP voltage. Enter –1 in
the CAP1 Voltage Divider RTop and RBot text boxes then
OPEN will be displayed in both text boxes.
USING THE LTC3350 SOFTWARE

11
dc1937bf
DEMO MANUAL DC1937B
The DC1937B standard configuration is designed for
supercapacitors of 50F or less. The standard configura-
tion measures the time it takes to discharge the capacitor
stack by 200mV at 10mA to calculate the capacitance.
Larger supercapacitors have larger leakage currents,some
over a milliamp, causing an inaccuracy in the capacitive
measurement. To increase the measurement accuracy,
the capacitor test current can be increased by loading
the capacitor stack with external resistors, R28 and R29,
during the measurement. The low threshold N-MOSFET,
M6, is controlled by the ITST pin which turns on the load
when needed.
OPTIONAL EXTERNAL TEST CURRENT
USING LARGE CAPACITORS
Figure 9. External Test Current
Larger capacitors also take longer to balance. If one ca-
pacitor is far enough off balance that it reaches the shunt
voltage before the capacitor stack is fully charged. The
charge current effectively is reduced to the shunt current
until the capacitor stack is fully charged. The standard
DC1937B board is set up for a 500mA maximum shunt
current. This current can be increased by turning on exter-
nal shunt resistors across each capacitor, R30 thru R36.
The controlling FETs, M7 thru M10, are turned on from
the voltage drop across the corresponding shunt resistor
whentheshunt regulator turns on. The 2.7Ω shunt resistors
between the supercapacitor and the CAPx pin as shown in
Figure 10 can be used to provide a larger shunt current.
Figure 10. High Current Shunting
I
SHUNT =
V
SHUNT
2•RSHUNT
+
V
SHUNT
RSHUNT(OPT)
The circuit in Figure 10 allows a larger shunt current to
protect the capacitors and charge up to the maximum
capacitor stack voltage faster but it does not increase the
balancing current.
Having a larger balancing current will help keep the large
capacitors in balance and may prevent the shunt voltage
from being reached. It will also reduce the capacitor volt-
age from the shunt voltage faster after shunting stops and
balancing begins. This is accomplished by increasing the
shunt resistors from 2.7Ω to at least 250Ω and up to 1kΩ.
Using resistors close to 250Ω will cause the balancing
currents to be smaller, less than 10mA with capacitor volt-
ages below 1.8V. Increasing the resistance much above
1kΩ can cause ADC measurement inaccuracies. The ITST
resistor must be increased to 1MΩ or greater; 10MΩ if
possible, to reduce the voltage drop across the CAP4 shunt
resistor, R20, from the internal current source during the
capacitancemeasurement. The circuitin Figure11provides
up to a 2A shunt/balance current and a 200mA capacitor
measurement test current.

12
dc1937bf
DEMO MANUAL DC1937B
USING LARGE CAPACITORS
Figure 11. High Current Balancing/Shunting
CALCULATING THE CAPACITANCE
The calculation for the standard DC1937B is:
CSTACK =
R
T
R
TST
•336µF •MEAS_CAP
for large scale and
CSTACK =
R
T
RTST
•3.36µF •MEAS_CAP
for small scale.
When using a capacitor stack with external balancing
resistors or any other external load on the capacitor
stack, those currents need to be added in the capacitor
measurement calculation. The following equations can be
used to calculate the capacitor test current when external
test load resistors and balance resistors are used.
Time = RT(in Ω) • 5.6e-5 for large scale.
Time = RT(in Ω) • 5.6e-7 for small scale.
ITST _EXT ≅
V
CAP
– 0.1V
RITST _ EXT
IBAL ≅VCAP – 0.1V
RBAL _ TOTAL
ITST ≅1.197V
RITST _ EXT
C=(ITST +ITST _EXT +IBAL )• TIME
0.2V

13
dc1937bf
DEMO MANUAL DC1937B
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 4 C2-C5 CAP, ELECTRIC DOUBLE LAYER, 10F, 2.7V NESSCAP, ESHSR 0010C0 002R7
2 1 C8 CAP, CHIP, COG, 120pF, ±5%, 25V, 0402 MURATA, GRM1555C1E121JA01D
3 2 C10, C25 CAP, CHIP, X5R, 0.1µF, ±10%, 25V, 0402 TDK, C1005X5R1E104K050BC
4 1 C11 CAP, CHIP, X5R, 1µF, ±10%, 25V, 0603 MURATA, GRM188R61E105KA12D
5 3 C12, C16, C24 CAP, CHIP, X7R, 0.1µF, ±10%, 16V, 0402 MURATA, GRM155R71C104KA88D
6 1 C13 CAP, CHIP, X5R, 4.7µF, ±10%, 6.3V, 0603 TDK, C1608X5R0J475K080AB
7 1 C14 CAP, CHIP, X5R, 1µF, ±10%, 16V, 0402 TDK, C1005X5R1C105K050BC
8 1 C15 CAP, 27µF, 25V, ALUM. ELECTRO, 20%, 6.3 × 4.5 SUN ELECT, 25HVH27M
9 1 C18 CAP., 0.01μF, X7R, 16V, 10%, 0402 AVX, 0402YC103KAT2A
10 :2 C19, C20 CAP, CHIP, X5R, 47µF, ±20%, 25V, 1206 TDK, C3216X5R1E476M160AC
11 2 C22, C23 CAP, CHIP, X5R, 2.2µF, ±10%, 25V, 0402 TDK, C1005X5R1E225K050BC
12 4 C26, C27, C28, C29 CAP, CHIP, X5R, 22μF, ±10%, 16V, 0805 TDK, C2012X5R1C226K125AC
13 1 D1 DIODE, SWITCHING, 80V, 0.125A, SOD-523 DIODES INC, 1N4448HWT-7
14 1 L1 IND., PWR., SHIELDED, 3.3μH, 20% COILCRAFT, XAL7030-332MEB
15 2 M1, M4 FET, N-MOS, 20V, 16A, POWER-PAK 1212-8 VISHAY, SIS438DN-T1-GE3
16 2 M2, M3 MOSFET N-CH 25V, 40A TSDSON-8 INFINEON, BSZ060NE2LS
17 1 R3 RES, CHIP, 649kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW0402649KFKED
18 1 R4 RES, CHIP, 162kΩ, ±1%,1/16W, 0402 VISHAY, CRCW0402162KFKED
19 1 R5 RES, CHIP, 787kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW0402787KFKED
20 1 R6 RES, CHIP, 100kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW0402100KFKED
21 5 R7, R20, R23, R24, R25 RES, CHIP, 2.7Ω, ±1%, 1/2W, 0805 WIDE ROHM SEMI, LT R 10EVHFL2R70
22 2 R8, R9 RES, CHIP, 100kΩ, ±5%, 1/16W, 0402 VISHAY, CRCW0402100KJNED
23 3 R12, R13, R14 RES, CHIP, 1kΩ, ±5%, 1/16W, 0402 VISHAY, CRCW04021K00JNED
24 1 R19 RES, CHIP, 0Ω JUMPER, 1/16W, 0402 VISHAY, CRCW04020000Z0ED
25 1 R21 RES, CHIP, 121Ω, ±1%, 1/16W, 0402 VISHAY, CRCW0402121RFKED
26 1 R22 RES, CHIP, 71.5kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW040271K5FKED
27 1 R26 RES, CHIP, 866kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW0402866KFKED
28 1 R27 RES, CHIP, 118kΩ, ±1%, 1/16W, 0402 VISHAY, CRCW0402118KFKED
29 1 RSNSC RES, CHIP, 6mΩ, ±1%, 1W, 1632 SUSUMU, PRL1632-R006-FT1
30 1 RSNSI RES, CHIP, 16mΩ, ±1%, 1W, 1632 SUSUMU, PRL1632-R016-FT1
31 1 U1 SUPERCAP BACKUP CONTROLLER LINEAR TECH., LTC3350EUHF#PBF
Additional Demo Board Circuit Components
32 1 C1 CAP, CHIP, X7R, 0.1µF, ±10%, 16V, 0402 MURATA, GRM155R71C104KA88D
33 2 C6, C7 CAP, CHIP, X5R, 1µF, ±10%, 25V, 0603 MURATA, GRM188R61E105KA12D
34 0 C9, C17 CAP, CHIP, 0402
35 0 C21 CAP, 6.3 × 4.5
36 3 D2, D3, D4 LED, SUPER RED, 660nm, 0603, 1.6 × 0.8mm LUMEX, SML-LX0603SRW-TR
37 0 D5 DIODE ZENER, 5.6V, 250mW, DFN1006-2 DIODES INC, BZT52C5V6LP-7
PARTS LIST

14
dc1937bf
DEMO MANUAL DC1937B
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
38 2 R1, R2 RES, CHIP, 20Ω, ±1%, 1/16W, 0402 VISHAY, CRCW040220R0FKED
39 0 R10, R11 RES, CHIP, 0402
40 3 R15, R16, R18 RES, CHIP, 5.1kΩ, ±5%, 1/16W, 0402 VISHAY, CRCW04025K10JNED
41 1 R17 RES, CHIP, 1MΩ, ±5%, 1/16W, 0402 VISHAY, CRCW04021M00JNED
42 0 R28-R29 RES, CHIP, 2W, 2512
43 0 R30-R37 RES, CHIP, 2W, 2512
44 2 R38, R39 RES, CHIP, 2.4MΩ, ±5%, 1/16W, 0402 VISHAY, CRCW04022M40JNED
45 1 M5 MOSFET, N-CH 20V, 5.9A, SOT-23 VISHAY, SI2374DS-T1-GE3
46 0 M6 MOSFET, N-CH 20V, 5.9A, SOT-23 VISHAY, SI2374DS-T1-GE3
47 0 M7-M10 MOSFET, N-CH 8V, 12A, POWERPAK SC-70 6L VISHAY, SIA436DJ
48 1 U2 I2C EEPROM MICROCHIP, 24LC025-I/ST
Hardware: For Demo Board Only
49 10 E1- E10 TURRET, 0.09 DIA MILL-MAX, 2501-2-00-80-00-00-07-0
50 6 E11- E16 TURRET, 0.061 DIA MILL-MAX, 2308-2-00-80-00-00-07-0
51 1 J1 CONN, 2x14 2mm HEADER MOLEX, 87831-1420
52 1 JP1 HEADER, 3PINS, 2mm WURTH, 62000311121
53 1 XJP1 SHUNT 2mm 1X3 WURTH, 60800213421
54 4 STAND-OFF, NYLON 0.50 tall KEYSTONE, 8833(SNAP ON)
55 1 FAB, PRINTED CIRCUIT BOARD DC1937B-3

15
dc1937bf
DEMO MANUAL DC1937B
5 5
4 4
3 3
2 2
1 1
D D C C B B A A
6V BACKUP
10.8V - 20V
10.8V - 20V
UNLESS NOTED: RESISTORS: OHMS, 0402, 1%, 1/16W CAPACITORS: uF, 0402, 6.3V, 10%
12V NOMINAL
25W
X5R X5RX5R X5R
25W
DC590 INTVCC
PULL - UP PWR
OPT
0508
0508
0508
0508
0508
OPTIONAL EXTERNAL TEST CURRENT
OPTIONAL EXTERNAL SHUNT CURRENT
R38 AND R39 ARE FOR STAND-ALONE OPERATION ONLY AND THE I2C BUS IS NOT USED.
SMBUSALERT
ITST
ITST
GCAP4 GCAP3 GCAP2 GCAP1
CAP1
CAP4
CAP4 CAP3 CAP2
CAP3 CAP1
CAP1 CAP2 CAP3 CAP4
GCAP1
GCAP2
GCAP3
GCAP4
CAP2
VCC
VCC INTVCC
INTVCC
REVISION HISTORY DESCRIPTION DATEAPPROVEDECO REV
MMPRODUCTION FAB
-3 05-04-15
REVISION HISTORY DESCRIPTION DATEAPPROVEDECO REV
MMPRODUCTION FAB
-3 05-04-15
REVISION HISTORY DESCRIPTION DATEAPPROVEDECO REV
MMPRODUCTION FAB
-3 05-04-15
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY Fax: [phone]
Milpitas, CA 95035 Phone: [phone] McCarthy Blvd. LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
3
DEMO CIRCUIT 1937B
11
HIGH CURRENT SUPERCAPACITOR
N/A
LTC3350EUHF
NC
MM
BACKUP CONTROLLER AND SYSTEM MONITOR
05 - 04 - 15
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY Fax: [phone]
Milpitas, CA 95035 Phone: [phone] McCarthy Blvd. LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
3
DEMO CIRCUIT 1937B
11
HIGH CURRENT SUPERCAPACITOR
N/A
LTC3350EUHF
NC
MM
BACKUP CONTROLLER AND SYSTEM MONITOR
05 - 04 - 15
SIZE DATE:
IC NO. REV.
SHEET OF
TITLE:
APPROVALS
PCB DES.
APP ENG.
TECHNOLOGY Fax: [phone]
Milpitas, CA 95035 Phone: [phone] McCarthy Blvd. LTC Confidential-For Customer Use Only
CUSTOMER NOTICE
LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND
SCHEMATIC
SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS.
SCALE = NONE
www.linear.com
3
DEMO CIRCUIT 1937B
11
HIGH CURRENT SUPERCAPACITOR
N/A
LTC3350EUHF
NC
MM
BACKUP CONTROLLER AND SYSTEM MONITOR
05 - 04 - 15
RSNSC
0.006
PRL1632
U2 24LC025-I/ST
A0
1
SCLK
6
A2
3
VSS
4
SDA
5
A1
2
WP
7
VCC
8
C26 22uF 0805
16V
10%
E3
VOUT
R10 OPT
D S
G
M3
BSZ060NE2LS
7
4
1
2
3
6
8
5
R18 5.1K 5%
E7
CAP1
C28 22uF 0805
16V
10%
D S
G
M2 BSZ060NE2LS
7
4
1
2
3
6
8
5
C20
47uF
1206
25V
20%
M6
Si2374DS
R25
2.7
5%
R35
OPT
2W 2512
R27
118K
+
C15 27uF 25HVH27M 25V 20%
R31
OPT
2W 2512
R22
71.5K
R6
100K
R29
OPT
2W 2512
M5
Si2374DS
E12
CAPGD
C29 22uF 0805
16V
10%
+
C3 10F
2.7V
R36
OPT
2W 2512
TPA2
C17
OPT
R38 2.4M
5%
M9
SiA436DJ
R21
121
M7 SiA436DJ
R13 1K 5%
C14 1uF
16V
5.6V D5
BZT52C5V6LP
R33
OPT
2W 2512
C1 0.1uF 16V
C23 2.2uF 25V
R11
OPT
E14 GND
+
C2
10F
2.7V
TPB2
E1
VIN
C24 0.1uF 16V
R26
866K
R39 2.4M
5%
R19
0
C12 0.1uF 16V
R8
100K
5%
E13
PFO
C25
0.1uF
25V
M8 SiA436DJ
TPB1 C6
1uF 0603
25V
L1
3.3uH
XAL7030-332MEB
C18
10nF
16V
R16 5.1K 5%
R14 1K 5%
+
C5 10F
2.7V
D2
PFO RED
C22 2.2uF 25V
JP1
+
C21 OPT 6.3 DIA
C19
47uF
1206
25V
20%
C13
4.7uF
0603
M10
SiA436DJ
C11
1uF
0603
25V
D
S
G
M1
SiS438DN
7
4
1 2 3
6 8 5
RSNSI
0.016
PRL1632
R1 20
R37
OPT
2W 2512
D4
SMBALERT
RED
E11 SMBALERT
D
S
G
M4 SiS438DN
7
4
1
2
3
6
8
5
E9
VCAP
10V
R12
1K
5%
E16
GPI
R20
2.7
5%
TP2
SCL R7
2.7
5%
D1
1N4448HWT
SOD-523
+
C4 10F
2.7V
U1
LTC3350EUHF
VCAP
21
PFI
37
CAP_SLCT1
36
PFO
38
PGND
39
CFP
17
CFN
18
BST
26
BGATE
27
SMBALERT
3
CAPFB
6
OUTFB
7
SGND
8
RT
9
INFET
33
VOUTSN
30
VOUTSP
31
VOUTM5
32
VIN
34
SCL
1
SDA
2
ICAP
22
VCC2P5
23
SW
24
TGATE
25
CAP2
14
CAP3
15
CAP4
16
CAP_SLCT0
35
VCAPP5
19
OUTFET
20
INTVCC
29
DRVCC
28
CAPGD
4
VC
5
GPI
10
ITST
11
CAPRTN
12
CAP1
13
R34
OPT
2W 2512
R2
20
D3
CAPGD
RED
J1
HD2X7
+
1
+
3
+
5
+
7
+
9
+
11
+
13
+
2
+
4
+
6
+
8
+
10
+
12
+
14
R30
OPT
2W 2512
E5
CAP3
TP1
SDA
R9
100K
5%
E10
GND
E4
GND
R15 5.1K 5%
R5
787K
R23
2.7
5%
C7
1uF
0603
25V
R4
162K
E15
GND
E8
GND
C27 22uF 0805
16V
10%
E2
GND
R28
OPT
2W 2512
E6
CAP2
C9
OPT
TPA1
R32
OPT
2W 2512
C16 0.1uF 16V
R24
2.7
5%
R17
1M
5%
C10
0.1uF
25V
R3 649K
C8
120pF
25V 5%
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SCHEMATIC DIAGRAM

16
dc1937bf
DEMO MANUAL DC1937B
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
[phone] ●FAX: [phone] ●www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2015
LT 0715 • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application
engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation