Linear Technology DC1296A User manual

DESCRIPTION
Demonstration Circuit DC1296A is a High Efficiency
USB Power Manager + Dual Buck + Buck-Boost Con-
verters featuring the LTC®3556. The LTC3556 is a
highly integrated power management and battery
charger IC for Li-Ion/polymer battery applications. It
includes a high efficiency current limited switching
PowerPath manager with automatic load prioritization,
a battery charger, an ideal diode and three general
purpose synchronous step-down switching regulators.
Designed specifically for USB applications, the
LTC3556’s switching power manager automatically
limits input current to a maximum of either 100mA or
500mA for USB applications or 1A for AC-powered
applications. Unlike linear PowerPath controllers, the
LTC3556’s switching input stage transmits nearly all of
the 2.5W available from the USB port to the system
load with minimal power wasted as heat. This feature
allows the LTC3556 to provide more power to the ap-
plication and eases the constraint of thermal budgeting
in small spaces. The two buck switching regulators
can provide up to 400mA while the buck-boost regula-
tor can deliver 1A. The output voltage of one buck and
the buck-boost can be adjusted, over a 2 to1 range, via
the I2C channel. The entire product can be started from
an external push button and subsequently controlled
via I2C. The LTC3556EUFD is available in a 28-pin
(4mm × 5mm × 0.75mm) QFN surface mount pack-
age. Design files for this circuit board are available,
call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation. PowerPath is a
trademark of Liner Technology Corporation.
PERFORMANCE SUMMARY Specifications are at T
A
= 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VBUS Bus Input Voltage Range 4.35 6 V
LDO3V3 3.3V LDO Output Voltage Range 3.1 3.4 V
VBAT Battery Float Voltage Constant Voltage Mode 4.15 4.23 mA
I
BAT
Battery Charge Current Constant Current Mode, R
PROG
= 2.00k 485 515 mA
V
OUT1
Regulator 1 Output Voltage IOUT1 ≤ 400mA 0.8 1.6 V
V
OUT2
Regulator 2 Output Voltage IOUT2 ≤ 400mA 1.7 1.8 1.9 V
V
OUT3
Regulator 3 Output Voltage IOUT3 ≤ 1A 2.65 3.3 V
OPERATING PRINCIPLES
The LTC3556 is a Li-Ion battery charger/power manager
with two Buck regulators and Buck-Boost regulator. The
LTC3566 also contains an integrated Buck regulator that
can provide the pre-regulation function, called Bat-
Track™, from the USB input supply. This allows for
minimal power dissipation in the charger. The load pre-
sented to the USB port can be programmed to comply
with the USB standards. This load can be set to 100mA,
or 500mA, as negotiated with the USB host, and is pro-
grammed using the I
2
C channel and the CLPROG pin re-
sistance.
The current that the charger supplies to the battery is
also programmable via the PROG pin resistance. The
current available, simultaneous to charging the battery, is
DEMO CIRCUI
T
DC1296
A
QUICK START GUID
E
LTC3556EUFD: High Efficiency
USB Power Manager with Dual Buck
and Buck-Boost DC/DCs
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
DC1296A
HIGH EFFICIENCY USB POWER MANAGER + DUAL BUCK + BUCK-BOOST
LTC3556EUFD
2
the difference between the allowable USB load and the
battery charging current.
The LTC3556 also has an ideal diode function which al-
lows the maximum energy to be extracted from the bat-
tery. The ideal diode function supports an optional ex-
ternal MOSFET for higher battery currents.
The output voltage of one of the Buck regulators
(VOUT1) and the Buck-Boost can be changed via the I
2
C
channel, providing a 2 to 1 range of control.
The output regulators can be enabled, as a group, by the
ENALL pin, or individually over the I
2
C channel. In addi-
tion, the sequence of regulator startup can be controlled
via the SEQ pin.
Figure 1: Y=VOUT1, BLU=VOUT2, PK=VOUT3, GRN = ENALL, SEQ = 0V
Figure 2: Y=VOUT1, BLU=VOUT2, PK=VOUT3, GRN = ENALL, SEQ = VOUT
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
DC1296A
HIGH EFFICIENCY USB POWER MANAGER + DUAL BUCK + BUCK-BOOST
LTC3556EUFD
3
SOFTWARE GUI
The DC1296A Demo Circuit can be controlled from a
software GUI. Most of the features of the
LTC3556EUFD are only accessible via the I
2
C channel.
When the QuikEval program is active and a DC590
with a DC1296A connected and attached to the USB
cable, the “LTC3556” form should automatically pop
up and be fully operational:
SOFTWARE OPERATION
The software GUI automatically opens the control
panel shown above. This control panel allows con-
trol of most major functions of the LTC3556. Please
note that the SEQ has no I
2
C channel equivalent.
And that the ENALL signal is wire OR’ed with indi-
vidual regulator enable regulator signals from the I
2
C
channel. Consequent to this, if the ENALL signal is
high, the regulators will be enabled regardless of the
state of the I
2
C channel regulator control bits.
Register A and Register B display
These are not writeable and are provided as a pro-
gramming aid. The current value of the I2C A and B
register are displayed.
Update button
Forces an immediate update of the I2C registers.
Autoupdate button
If enabled (default) will update the I2C channel
whenever something is changed.
Battery charger button
If enabled (default) the battery charger in the
LTC3556 will be enabled, and vice versa.
VOUT1~VOUT3 buttons
Individually enable or disable the three voltage regu-
lators. These only function if the ENALL pin is held
low.
Switchmode Regulators mode
Set the mode of operation of all the switchmode
regulators. Since VOUT3 is a Buck-Boost regulator,
the interpretation of the bits is different.
VOUT1 and VOUT3 sliders
Allow control of voltage regulator 1 and 3 output
voltages by adjusting the respective reference DACs.
VOUT1~3 output and reference voltages
These are not writeable, but reflect the current state
of the reference DACs, and feedback resistors.
Change feedback divider resistor values button
This opens the form:
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
DC1296A
HIGH EFFICIENCY USB POWER MANAGER + DUAL BUCK + BUCK-BOOST
LTC3556EUFD
4
This form allows the feedback resistor divider net-
work on each regulator to be changed. The informa-
tion changed here, is saved, and is durable from
session to session. However, the factory values can
be recovered by pressing the “Restore defaults” but-
ton
QUICK START PROCEDURE
Complete the Quick Start Procedure outlined in the
Quick Start Guide for Demo Circuit 590 available
from the Linear Technology Web Site, prior to pro-
ceeding.
Refer to Figure 2 for the proper measurement
equipment setup and jumper settings and follow the
procedure below.
NOTE. When measuring the input or output voltage ripple, care
must be taken to avoid a long ground lead on the oscilloscope
probe. Measure the input or output voltage ripple by touching the
probe tip directly across the VBUS or VOUT(x) and GND terminals.
See Figure 2 for proper scope probe technique.
1. Set PS1 to 5.0V, and PS2 to 3.6V. Using the
LTC3556 GUI click on “5X Mode(500mA)”. In-
crease Ld2 to 200mA. Measure VOUT (VM6) ≈
3.68V, and I(VBUS) (AM1) ≈ 454mA.
VBUS is 5V, and can supply up to 500mA, or
2.5W. VOUT is being loaded at 200mA +
≈454mA (battery charge current) ≈654mA, so
VOUT will be 2.5W/0.654A ≈ 3.80V.
2. Using the LTC3556 GUI click on “10X Mode(1A)”
under Average Input Current Limit Setting.
Measure VOUT (VM6) and IBAT. Measure VOUT
(VM6) ≈ 3.97V, and I(VBUS) (AM1) ≈ 510mA.
The input power limit is now higher than the
power load at VOUT, so VOUT rises to 3.97V ≈
(V(
BAT) + 0.35V).
3.
Set V(BAT) (PS2) to 2.5 V. Measure the battery
Current IBAT in trickle charge mode. Remove
the NTC jumper (JP1) and observe the CHRG
LED slow blinking rate (1.5Hz at 50% Duty Cy-
cle). Reinstall the NTC jumper (JP1). When
V(BAT) is below 2.85V (Typ.), the battery
charger attempts to trickle charge the battery up
above this threshold at ≈ I
CHARGE
/10 = 50mA.
When the battery charger detects a fault such as
the NTC pin signaling the battery is too cold or
too hot, it signals this by pulsing the CHRG pin at
a frequency and duty cycle that identifies the re-
ported fault.
4. Set the voltage on the BAT pin (PS2) to 4.21V.
Once the battery reaches the float voltage, the
battery charger switches from Constant Current
(CC) mode to Constant Voltage (CV) mode. The
purpose of Constant Voltage mode is keep the
battery “topped off” at the float voltage. If the
battery is unloaded, this current should be very
small.
5. With PS1 set at 5V, set the voltage on BAT (PS2)
to 3.6V. Set Ld1 to zero current and set ENALL
jumper (JP2) to “LO. Verify that the GOODALL
LED is lit. The GOODALL LED lights red when
one or all of the regulators is out of regulation, or
when all the regulators are off.
6. Set the ENALL jumper (JP2) to “Hi” to turn on
VOUT1-VOUT3. Observe the start-up sequence
with an oscilloscope, measure VOUT1, VOUT2
and VOUT3 and observe the state of the
POWERGOOD ALL LED. The sequencing of
regulators VOUT1, 2, & 3 is controlled by the
state of the SEQ pin. The SEQ pin is a three state
input to the LTC3556, and three sequences are
programmable. There is no equivalent to the
SEQ pin in the I
2
C channel. SEQ is grounded so
the power supply sequence should be VOUT1
then VOUT2, then VOUT3.
7. Move the SEQ jumper (JP3) to “3->1->2”.
8. Set ENALL jumper (JP2) to “LO.
9. Set the ENALL jumper (JP2) to “Hi” to turn on
VOUT1-VOUT3. Observe the start-up sequence
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
DC1296A
HIGH EFFICIENCY USB POWER MANAGER + DUAL BUCK + BUCK-BOOST
LTC3556EUFD
5
with an oscilloscope and the state of the
POWERGOOD ALL LED. The SEQ is floating so
the power supply sequence should VOUT3 then
VOUT1, then VOUT2.
10. Move the SEQ jumper (JP3) to “1->3->2”.
11. Set ENALL jumper (JP2) to “LO.
12. Set the ENALL jumper (JP2) to “Hi” to turn on
VOUT1-VOUT3. Observe the start-up sequence
with an oscilloscope and the state of the
POWERGOOD ALL LED. The SEQ pin is now at
VOUT, so the power supply sequence should be
VOUT1 then VOUT3, then VOUT2.
13. Move the SEQ jumper (JP3) to “1->2->3”, and
set ENALL jumper (JP2) to “LO”. Use the
LTC3556 demonstration software to turn on all
three regulators simultaneously. Do this by en-
suring that “AUTOUPDATE OFF” is displayed, se-
lecting “VOUT1 ON”, “VOUT2 ON”, and “VOUT3
ON”, then clicking “UPDATE ALL”. Observer
Startup sequence of regulators, and verify that
the PGOODALL LED is unlit. This demonstrates
that startup sequence of the regulators is con-
trolled by the SEQ pin, even when the regulators
are enabled via the I
2
C channel. However, there
is an enable bit for each regulator, as opposed to
the ENALL pin, in the I
2
C channel, so some care
must be taken to enable all three regulators si-
multaneously.
14. Ensure that PS1 is 5V, PS2 is 4.21V. Set the
GUI autoupdate mode to “AUTOUPDATE ON”.
With the load on VOUT1 (Ld5) at 400mA, VOUT2
(Ld3) at 400mA, and VOUT3 (Ld4) at 1A. Meas-
ure VOUT (VM6) ≈ 4.2V, VOUT1 (VM10) ≈ 1.6V
± 3%, VOUT2 (VM8) ≈ 1.8V ± 3% and VOUT3
(VM9) ≈ 3.27V ± 3%. Observe the state of
PGOODALL LED. VOUT1, VOUT2, and VOUT3
load VOUT. The load on VOUT is (1.6V * 0.4A) +
(1.8V * 0.4A) + (3.3V * 1.0A) = 4.67W. The
power available from the VBUS input is 5V * 1A
= 5W, but the efficiency of the VOUT regulator is
not 100%. VOUT should be a 4.35V ≈ (V( BAT) +
0.35V), but has drooped to 4.2V because the
load is at the maximum power available from the
VBUS input.
15. Using the LTC demonstration software set
VOUT1 and VOUT3 reference voltage to 425mV.
Setting VOUT3 reference voltage to 425mV, may
require enabling operation below 2.75V. Do this
in the Voltage regulator tab of the “Set resistor
values dialogue”. Dismiss any efficiency warning
that is posted. Measure VOUT (VM6) ≈ 4.2V,
VOUT1 (VM10) ≈ 0.85V ± 3%, VOUT2 (VM8) ≈
1.8V ± 3% and VOUT3 (VM9) ≈ 1.65V ± 3%.
Observe state of PGOODALL LED. The feedback
reference voltages of regulators VOUT1 and
VOUT3 have been approximately halved to
425mV. Consequently the output voltage will
approximately halve as well.
16. Set VOUT1 load (Ld5), VOUT2 load (Ld3), and
VOUT3 load (Ld4), to 0.
17. Set PS1 and PS2 to 0V. Disconnect all test
equipment, and close LTC3556 GUI software
window.
18. Reset the Jumpers to their default position.
See the LTC3556 data sheet for more information on
how this part performs.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
DC1296A
HIGH EFFICIENCY USB POWER MANAGER + DUAL BUCK + BUCK-BOOST
LTC3556EUFD
6
Figure 1. Proper Measurement Equipment Setup for DC1296A
VIN GND
Figure 2. Measuring Input or Output Ripple
PS1 -
4.35V - 5.5V supply
2A +
Ld2 -
0V - 5V
2A +
- +
AM3
Ld1 -
0V - 5V
0.1
A
+
- +
AM2
-
+
VM4
-
+
VM1
- PS2
0V - 5V supply
+ 5
A
3.6 Ω
+
-
VM7
- +
AM4
+
-
VM8
+ -
- Ld3
0V - 5V
+ 2
A
AM5
+
-
VM9
+
-
VM10
+ -
AM6
- Ld4
0V - 5V
+ 2
A
+ -
- Ld5
0V - 5V
+ 2
A
AM7
VM5
-
+
VM6
-
+
+ -
-
+
AM1
VM2
-
+
VM3
14 pin ribbon
cable
Linear Technology
DC590B USB to I2C
converter
PC running
LTC3556 demon-
stration software
USB
cable
Note: All connections from equipment should be Kelvin connected directly to the board
pins which they are connected on this diagram and any input or output leads should be
twisted pair.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
DC1296A
HIGH EFFICIENCY USB POWER MANAGER + DUAL BUCK + BUCK-BOOST
LTC3556EUFD
7
Figure 3. Circuit Schematic
C10
2.2uF
16V 0603
R1
1.0
5%
E5
PROG
E12
VOUT1
1->3->2
E14
BAT
R28
1k 5% 0603
1.25A
R21
20 5% TP6
INJ1
E9
GND
TP3 ID
R23 715k
L3 4.7uH
1098AS-4R7M
NTC-EXT
C15 10uF
0603 6.3V
1->2->3
3.3V
R13 15k
E16
PGOODALL
E17
GND
E18
VOUT
C7
10pF ±0.5pF
R9 0
E1
VBUS
R7 0
R3 3.01k
U1
LTC3556EUFD
25 29
24
2
20
3
21 9 12 14 1 23 22 26 11
28 27 13
8
10 16
18 7 19 17 5 4 6 15
VBUS
GND
VOUT
CLPROG PROG NTC
CHRG
SWAB3
VOUT3
SWCD3
LDO3V3
BAT
GATE
SW
VIN3
ENALL SEQ SCL
VC3
DVCC SDA
VIN2
FB3
SW2
FB2
VIN1
SW1
FB1
PGOODALL
25mA
Q1 Si2333DS
1
3 2
E7
GND
INT R8
0
TP4
INJ3
C6
330pF 5%
R15
121k
E8
VOUT3
C12 10uF
6.3V 0603 20%
R26 1.0 5%
JP1
OPT
C4
0.1uF
16V
3->1->2
C2 10uF
0603
6.3V 20%
R17 20 5%
J2 DF3-3P-2DSA
1 2 3
BAT GND NTC-EXT
1A
R19 1MEG
L1 2.2uH
LPS4018-222MLC
Vout
R16 324k
R18
20 5%
USBMINI-B
J1
1 2 3 4 5
VBUS
D-
D+
ID
GND
J3 HD2X7
1 3 5 7 9
11 13
2 4 6 8 10 12 14
+ + + + + + +
+ + + + + + +
TP5INJ2
0.8V-1.6V
CHRG
E2
GND
R22
715k
C14
10pF ±0.5pF
R5
100K
E15 CHRG
C3
0.1uF
16V
1.8V
PGOODALL
C13
1uF 10V E11
GND
D2
RED
R29 0
JP3
C8
33pF 5%
C16
1uF
10V
L4 3.3uH
LPS4018-332
C9
22uF
0805
6.3V 20%
E6
NTC
VOUT
NTC
C11 10pF ±0.5pF
E4
GND
2.65V-3.3V
EXT
R2
8.25
R20 806k
R24 1.0 5%
D1
GREEN
R25 1.0 5%
OPT
SEQ
4.35V-5.5V
ENALL
R27
1k 5% 0603
Unless noted: Resistors: Ohms, 0402, 1%, 1/16W Capacitors: uF, 0402, 10%, 50V
NTC-EXT
R10
5.1K 5%
L2 4.7uH
1098AS-4R7M
E10
VOUT2
400mA
R14
105k
JP2
U2
24LC025I/ST
256X8
1 6 3
4
5
2 7
8
A0 SCLK A2
Vss
SDA
A1 WP
Vcc
400mA
HI
VBUS
R11
5.1K 5%
C1 10uF
0603 6.3V
20%
0.5A
R4 2.00k
C18
22uF 0805 6.3V 20%
R12
5.1K
5%
VFLOAT=4.2V
TP2 D+
VBUS
LO
C5
0.1uF
16V
C19 1uF 10V
TP1 D-
E13
GND
3.4V-4.7V
E3
CLPROG
R6
100K
E19
LDO3V3
C17
100uF
6.3V
1206
20%
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT
DC1296A
HIGH EFFICIENCY USB POWER MANAGER + DUAL BUCK + BUCK-BOOST
LTC3556EUFD
8
Figure 4. Bill of Materials
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