Linear Analog Devices DC2985A User manual

1
DEMO MANUAL DC2985A
Rev. 0
1
Rev. 0
DESCRIPTION
LT3380
Multi-Output Power Management Solution with 4 Buck
Switching and 3 LDO Linear Regulators with I2C
DC2985A is a multi-output power management solution
demonstration circuit, featuring the LT
®
3380. It contains
two 2.5A, two 1.5A synchronous step-down DC/DC regu-
lators and three 300mA LDO regulators.
All regulators can be enabled with external enable pins.
After the first regulator is enabled, the remaining enable
pins use a precision threshold to allow hardwire-pro-
grammed Power-Up Sequence.
All registered trademarks and trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
BOARD PHOTO
A micro-USB communication interface is integrated on
board to allow software GUI to write or read the registers
in LT3380 via its I
2
C serial port. This GUI can control
regulator enables, power-down sequencing, output volt-
age levels, dynamic voltage scaling, operation modes,
status reporting and other special functions.
Refer to LT3380 data sheet for more details on the electri-
cal specifications and the setting of its command registers.
Design files for this circuit board are available.
Specifications are at TA= 25°C
Figure1. DC2985A Board Photo
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Input Voltage Range 2.7 5.5 V
VBUCK1 BUCK1 Output Voltage BUCK1 Enabled, I(BUCK1) = 0A ~ 2.5A 1.20 V
VBUCK2 BUCK2 Output Voltage BUCK2 Enabled, I(BUCK2) = 0A ~ 2.5A 1.50 V
VBUCK3 BUCK3 Output Voltage BUCK3 Enabled, I(BUCK3) = 0A ~ 1.5A 2.48 V
VBUCK4 BUCK4 Output Voltage BUCK4 Enabled, I(BUCK4) = 0A ~ 1.5A 1.81 V
VLDO1 LDO1 Output Voltage LDO1 Enabled, I(LDO1) = 0A ~ 300mA 1.20 V
VLDO2 LDO2 Output Voltage LDO2 Enabled, I(LDO2) = 0A ~ 300mA 0.80 V
VLDO3 LDO3 Output Voltage LDO3 Enabled, I(LDO3) = 0A ~ 300mA 1.80 V

2
DEMO MANUAL DC2985A
Rev. 0
EFFICIENCY CURVES
Specifications are at TA= 25°C, fSW = 2.25MHz, VIN = 5V, without D1
BURST
PULSE
SKIPPING
FORCE
CONTINUOUS
LOAD CURRENT (mA)
1
10
100
1000
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
dc2985a G01
BURST
PULSE
SKIPPING
FORCE
CONTINUOUS
LOAD CURRENT (mA)
1
10
100
1000
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
dc2985a G02
BURST
PULSE
SKIPPING
FORCE
CONTINUOUS
LOAD CURRENT (mA)
1
10
100
1000
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
dc2985a G03
BURST
PULSE
SKIPPING
FORCE
CONTINUOUS
LOAD CURRENT (mA)
1
10
100
1000
0
10
20
30
40
50
60
70
80
90
100
EFFICIENCY (%)
dc2985a G04
BUCK1 1.2VOUT Efficiency BUCK2 1.5VOUT Efficiency
BUCK3 2.48VOUT Efficiency BUCK4 1.81VOUT Efficiency

3
DEMO MANUAL DC2985A
Rev. 0
TRANSIENT RESPONSE
Specifications are at TA= 25°C, fSW = 2.25 MHz, VIN = 5V
1.5A
100mA
BURST
PULSE SKIPPING
FORCE CONTINUOUS
50µs/DIV
I
OUT
2A/DIV
V
OUT
200mV/DIV
V
OUT
200mV/DIV
V
OUT
200mV/DIV
dc2985a G07
1.5A
100mA
BURST
PULSE SKIPPING
FORCE CONTINUOUS
50µs/DIV
I
OUT
2A/DIV
V
OUT
200mV/DIV
V
OUT
200mV/DIV
V
OUT
200mV/DIV
dc2985a G08
300mA
5mA
LDO1
LDO2
LDO3
50µs/DIV
V
OUT
2A/DIV
V
OUT
200mV/DIV
V
OUT
200mV/DIV
V
OUT
200mV/DIV
dc2985a G09
BUCK3 2.48VOUT Transient Response BUCK3 1.81VOUT Transient Response
LD01-LD03 Transient Response
2.5A
100mA
BURST
PULSE SKIPPING
FORCE CONTINUOUS
50µs/DIV
I
OUT
2A/DIV
V
OUT
200mV/DIV
V
OUT
200mV/DIV
V
OUT
200mV/DIV
dc2985a G05
2.5A
100mA
BURST
PULSE SKIPPING
FORCE CONTINUOUS
50µs/DIV
I
OUT
2A/DIV
V
OUT
200mV/DIV
V
OUT
200mV/DIV
V
OUT
200mV/DIV
dc2985a G06
BUCK1 1.2VOUT Transient Response BUCK2 1.5VOUT Transient Response

4
DEMO MANUAL DC2985A
Rev. 0
POWER UP SEQUENCE
Specifications are at TA= 25°C, fSW = 2.25MHz, VIN = 5V, IOUT = 100mA for all regulators
500µs/DIV
V
LDO3
V
LDO1
V
BUCK4
V
BUCK1
V
BUCK3
V
BUCK2
V
LDO2
V
PWR_ON
dc2985a G10
Regulators Power-Up Sequencing
QUICK START PROCEDURE
Follow the procedure below to familiarize yourself with
the DC2985A.
1. Refer to Figure2, configure the jumpers on the demo
board as follows:
JP1 = VIN
JP2 = VIN
JP3 = VIN
JP4-JP10 = DFT
JP11 = ON
JP13 = ON
2. Set PS1 to 5V, with 5A current limit. Turn on PS1. All
the regulators should come up in a default sequence:
B2 & B3 -> L2 -> B1 & B4 -> L1 & L3
3. The PGOOD LED D2 should stay off, indicating all out-
puts are in regulation. Check the output voltage of all
the regulators, they should read close to the following
values:
VVM1 = 1.2V
VVM2 = 1.5V
VVM3 = 2.48V
VVM4 = 1.81V
VVM5 = 1.2V
VVM6 = 0.8V
VVM7 = 1.8V
4. Set each electronic load to its corresponding current
level indicated in Figure2. Turn on each load. The
PGOOD LED D2 should stay off, indicating all the out-
puts are still in regulation under loads. Note that if there
are not enough electronic loads for all the regulators,
this test can be done sequentially.
5. Optional:The default input of the three LDOs are from
VIN. To increase the efficiency, the LDOs can be pow-
ered from BUCK3 by configuring JP1 to JP3 to V(B3).
They can also be powered from external source by
configuring these jumpers to EXT.
6. Optional:The power up sequence can also be pro-
grammed by configuring JP4 to JP10 to PGM/OFF.
Connect the SEQ_START to the EN_SEQ of the first
regulators to power up. Then connect the subsequent
regulators EN_SEQ to the corresponding VX_SEQ
according to the desired startup sequence. If EN_SEQ
of a regulator is not connected and the jumper is on
PGM/OFF position, this regulator is turned off.

5
DEMO MANUAL DC2985A
Rev. 0
JUMPER DESCRIPTION
JUMPER NAME FUNCTION POSITION DESCRIPTION
JP1-JP3 LDOXVIN Input for the LDOs V(B3) Input from BUCK3
EXT Input from External Source Connected to VIN_LDOXTurret
VIN Input from VIN Turret
JP4-JP10 BX_SEQ or
LX_SEQ
Power Up Sequence for the Regulators DFT Default Power Up Sequence
PGM/OFF Programmed Sequence/Regulator Off
JP12 PGOOD_LED Power On Master Enable and Disable
Status Selection
ON PWR_ON Allows Enable Pin Operation
OFF PWR_ON Inhibits Enable Pin Operation
JP13 PWR_ON_CTRL Enable/Disable Power Good LED
Indicator (Indicating Output not in
Regulation)
ON Power Good LED Indicator Enabled
EXT PWR_ON Status Controlled by External Source Connected to
PWR_ON Turret
OFF Power Good LED Indicator Disabled

6
DEMO MANUAL DC2985A
Rev. 0
TEST SETUP
VM6
VM4
LD6
300mA
LD4
1.5A
+
–
+
–
VM3 LD3
1.5A
+
–
+
–
+
–
+
–
VM2 LD2
2.5A
+
–
+
–
VM1 LD1
2.5A
+
–
+
–
VM7
LD7
300mA
+
–
+
–
PS1
5V, 5A
+
–
VM5
LD5
300mA
+
–
+
–
POWER UP SEQUENCE
PROGRAMMING SECTION
PC RUNNING LT3380
DEMONSTRATION SOFTWARE
MICRO-USB
CABLE
Figure2. Test Setup for DC2985A Demo Board

7
DEMO MANUAL DC2985A
Rev. 0
DEMO CIRCUIT OPERATION
Introduction to the DC2984A
The DC2985A a multi-output power management solu-
tion with I2C interface featuring the LT3380. It contains
four synchronous buck regulators and three LDO regula-
tors. Among the four buck regulators, BUCK1 and BUCK2
deliver up to 2.5A output current, while BUCK3 and BUCK4
deliver up to 1.5A output current. All three LDOs deliver
up to 300mA output current. BUCK1-BUCK4 have default
output voltages of 1.2V, 1.5V, 2.48V and 1.81V, respec-
tively. LDO1 and LDO2 have default output voltages of
1.2V and 0.8V respectively. These voltages are configured
by voltage dividers on the corresponding FB pins and can
be changed by the user. LDO3 has a fixed voltage of 1.8V.
The DC2985A also contains an isolated USB transceiver
and a micro-controller, allowing computer-based software
GUI to read/write the registers defined in the LT3380 via
its I2C serial port. User can control regulator enables,
power-down sequencing, output voltage levels, dynamic
voltage scaling, operating modes and status reporting.
Power Up Sequencing
The LT3380 regulators can be powered up in any desired
order by pin-strapping output rails to enable pins. The
enable pins have a 0.75V (typical) input voltage threshold.
If any enable is driven high, the remaining enable input
thresholds switch to an 400mV threshold. There is a built-
in 450µs delay from the enable pin threshold crossing to
the internal enable of the regulator.
The DC2985A has a default power up sequence. User
can also program the power up sequence by selecting
JP4-JP10 to PGM/OFF position and connecting the out-
put rails to the enable pins at the Power Up Sequence
Programming Section shown in Figure2. The start of the
sequence is the rising edge of the PWR_ON pin. PWR_ON
pin can be pulled up to VIN, pulled down to ground, or
connected to an external command source by selection
JP13, PWR_ON_CTRL jumper.
Figure3 illustrates BUCKX voltage when BUCK1-BUCK4
is programmed to start in an ascending order. The demo
board connection is shown as follows:
SEQ_START -> EN_B1_SEQ
VB1_SEQ -> EN_B2_SEQ
VB2_SEQ -> EN_B3_SEQ
VB3_SEQ -> EN_B4_SEQ
1ms/DIV
dc2985a F03
V
PWR_ON
5V/DIV
V
BUCK1
2V/DIV
V
BUCK2
2V/DIV
V
BUCK3
2V/DIV
V
BUCK4
2V/DIV
Figure3. Program BUCK1-BUCK4 Power Up
Sequence in Ascending Order
Regulator Enables
When JP4-JP10 is at PGM/OFF position, and no connec-
tion is made at the Power Up Sequence Programming
Section, all the regulators are disabled. Each regulator
can be individually enabled by its corresponding enable
turret at the edge of the demo board.
LDO Input Selection
The default input of each LDO is the general input of the
demo circuit, VIN. To reduce power loss of the LDOs, the
input source of each LDO can be changed to the output
of BUCK3 by connection corresponding LDOXVIN jumper
to V(B3). Each LDO can also be powered externally by
selecting the corresponding LDOXVIN jumper to EXT and
connecting a separate source to VIN_LDOX turret. Note
that the voltage of this external LDO source must not
exceed voltage.
Power Good Indicator
Power Good LED D2 is turned on when PGOOD pin on
LT3383 is pulled low. It indicates the one or more output
voltages of the enabled regulators are low. It will also be
on when no regulator is enabled.

8
DEMO MANUAL DC2985A
Rev. 0
Install the LT3380 GUI
The LT3380 GUI can be downloaded from Analog.com or
using QuickEval software. Double click the LT3380 GUI
installer ins3380.exe. A window as shown in Figure 4
will pop up. Select I accept the agreement and then click
Next to start the installation. The GUI application will be
installed at the following location:
C:\Program Files (x86)\LT C \LT3380 GUI
Start the LT3380 GUI
The LT3380 GUI applicaiotn should show up in the Recen-
tely added section when clicking the Windows button.
Before starting the GUI, please make sure that DC2985A is
connected to the PC with micro-USB cable. Click LT3380
GUI to start the GUI application. If LT3380 GUI cannot be
found in the Recentely added section, go to the LTC3380
GUI folder and double click em.3380.exe to start the GUI.
If DC2985A is powered up and successfully connected to
the PC with a micro-USB cable, the Dashboard of the GUI
will pop up, as shown in Figure6
USING LT3380 GUI
Figure4. License Agreement Window in GUI
Installation Process
Figure5. Completing Installation Window
Figure6. LT3380 GUI Dashboard Tab
Figure7. LT3380 GUI Engineering Tab
When the software is succefully installed, a window as
shown in Figure 5 will pop up. Click Finish to complete
the installation.
In this Dashboard tab, user can control the basic setups
of the regulators.
To get access to all the registers and change some
advanced setups of the regulators, click the Engineer-
ing tab next to the Dashboard tab. Figure7 shows the
LTC3380 Engineering tab.

9
DEMO MANUAL DC2985A
Rev. 0
To change the register setup, right click on the register,
and click Write Preset, then select the desired register
status. Figure8 shows an example of setting the register
to mask overtemperature warning.
The default setting of the Engineering tab is reading the
registers continuously. User can change this setting by
right click in the main window. User can also hide the
registers that are not used by clicking the checkbox in
the Categories section. Detailed description for all the
features in the GUI is in Window ->Show Help Guide on
the top left corner of the GUI.
Figure8. Changing Register Setup in Engineering Tab
USING LT3380 GUI

10
DEMO MANUAL DC2985A
Rev. 0
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 5 C1, C8-C11 CAP., 10μF, X5R, 10V, 20%,0603, AEC-Q200 TAIYO YUDEN, LMK107BBJ106MAHT
2 6 C2-C7 CAP., 1μF, X5R, 25V, 10%, 0402, AEC-Q200 MURATA, GRT155R61E105KE01D
3 4 C12, C15, C17, C19 CAP., 47μF, X5R, 6.3V, 20%, 0805, AEC-Q200 MURATA, GRT21BR60J476ME13L
4 4 C14, C16, C18, C20 CAP., 10pF, C0G, 50V, 5%, 0402, AEC-Q200 MURATA, GCM1555C1H100JA16D
5 1 C21 CAP., 0.1μF, X7R, 16V, 10%, 0402, AEC-Q200 MURATA, GCM155R71C104KA55D
6 2 L1, L2 IND., 0.82μH, PWR, 20%, AEC-Q200 COILCRAFT, XGL4020-821MEC
7 2 L3, L4 IND., 1.5μH, PWR, 20%, AEC-Q200 COILCRAFT, XGL4020-152MEC
8 2 Q1, Q2 XSTR., NPN, 40V, 200MA, SOT23-3 ON SEMICONDUCTOR, MMBT3904LT1G
9 1 R1 RES., 102k, 1%,1/16W, 0402, AEC-Q200 STACKPOLE ELECTRONICS, INC., RMCF0402FT102K
10 6 R2, R4, R6, R9, R13, R16
11 2 R3, R15 RES., 649k, 1%,1/16W, 0402 NIC, NRC04F6493TRF
12 4 R5, R8, R11, R14 RES., 20Ω, 1%,1/16W, 0402, AEC-Q200 NIC, NRC04F20R0TRF
13 1 R7 RES., 665k, 1%, 1/16W, 0402, AEC-Q200 NIC, NRC04F6653TRF
14 1 R10 RES., 412k, 1%, 1/16W, 0402 NIC, NRC04F4123TRF
15 1 R12 RES., 1.07M, 1%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW04021M07FKED
16 10 R17, R18, R20-R26, R76 RES., 10k, 5%, 1/16W, 0402, AEC-Q200 NIC, NRC04J103TRF
17 2 R27, R28 RES., 4.7k, 5%, 1/16W, 0402, AEC-Q200 NIC, NRC04J472TRF
18 2 R30, R31 RES., 1k, 5%, 1/16W, 0402, AEC-Q200 NIC, NRC04J102TRF
19 8 R33-R39, R61 RES., 10k, 1%, 1/16W, 0402, AEC-Q200 VISHAY, CRCW040210K0FKED
20 7 R40-R46 RES., 10k, 1%,1/10W, 0603, AEC-Q200 PANASONIC, ERJ3EKF1002V
21 7 R54-R60 RES., 5.11M, 1%, 1/10W, 0603, AEC-Q200 VISHAY, CRCW06035M11FKED
22 2 R62,R75 RES., 100k, 5%, 1/16W, 0402, AEC-Q200 NIC, NRC04J104TRF
23 1 U1 IC, MULTI-OUTPUT POWER, 40-PIN ANALOG DEVICES, LT3380EUJM
Additional Demo Board Circuit Components
1 2 C22, C23 CAP., 22pF, NP0, 50V, 5%, 0402 WURTH ELEKTRONIK, 885012005057
2 2 C24, C31 CAP., 1μF, JB, 10V, 20%, 0402 TDK, CGB2A1JB1A105M033BC
3 1 C25 CAP., 2.2μF, X5R, 10V, 20%, 0402 WURTH ELEKTRONIK, 885012105013
4 1 C26 CAP., 10μF, X5R, 6.3V, 20%, 0603 MURATA, GRM188R60J106ME47D
5 4 C27-C30 CAP., 0.1μF, X5R, 10V, 20%, 0402 WURTH ELEKTRONIK, 885012105010
6 1 C32 CAP., 0.01μF, X7R, 25V, 10%, 0402 WURTH ELEKTRONIK, 885012205050
7 2 D1, D2 LED, RED, WATER CLEAR, 0603 WURTH ELEKTRONIK, 150060RS75000
8 1 D3 LED, BRIGHT GREEN, WATERCLEAR, 0603 WURTH ELEKTRONIK, 150060VS75000
9 1 D4 LED, YELLOW, WATERCLEAR, 0603 WURTH ELEKTRONIK, 150060YS75000
10 1 L5 IND., CHIP BEAD, 6A,0.01Ω, L-MPZ2012 TDK, MPZ2012S300AT000
11 3 M1-M3 XSTR., MOSFET, DUAL N-CH, 0.28A, SOT-563 DIODES INC., 2N7002VAC-7