Linear Technology DC1123 User manual

DC1123 QUICK START GUIDE
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DESCRIPTION
Demonstration circuit 1123 is a Linear USB Battery
Charger w ith Dual Buck Regulators featuring the
LTC35 2. The LTC35 2 is a quad high efficiency mono-
lithic synchronous step-dow n regulator w ith an I
2
C inter-
face. Tw o regulators are externally adjustable and can
have their feedback voltages programmed betw een
425mV and 800mV in 25mV (Type A). The other tw o
regulators are fixed output regulators w hose output volt-
ages can be programmed betw een 00mV and 3.775V in
25mV steps (Type B). All four regulators operate inde-
pendently and can be put into pulse skip, LDO, Burst
M ode operation or forced Burst M ode operation through
I
2
C control. The Type A regulators have separate RUN
pins that can be enabled if I
2
C control is unavailable.
The 2.85V to 5.5V input range makes the LTC-35 2 ide-
ally suited for single Li-ion battery pow ered applications.
At low output load conditions, the regulators can be
sw itched into LDO, Burst M ode operation or forced Burst
M ode operation, extending battery life in portable sys-
tems. The quiescent current drops to under 100µA w ith
all regulators in LDO mode and under 0.1µA w hen all
regulators are shut dow n
Sw itching frequency is internally set to 2.25M Hz, allow -
ing the use of small surface mount inductors and capaci-
tors. All regulators are internally compensated.
The LTC35 2 is offered in a low profile 3mm  3mm
QFN package.
Design files for this circuit board are available. Call
the LTC factory.
L , LTC, LTM , LT, Burst M ode, are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective ow ners.
TABLE 1. Typical Specifications (25°C)
Input Voltage Range: V
CC
2.85V to 5.5V (Subject to dropout)
P 00A 0.9 V to 1.82V, 00mA (M ax)
P 00B 1.20V to 3.775V, 00mA (M ax)
P400A 0.80V to 1.51V, 400mA (M ax)
P400B 0. 0V to 3.775V, 400mA (M ax)
OPERA TING PRINCIPL ES
The LTC35 2 is a highly integrated pow er management
IC that contains four I
2
C controllable, monolithic, high
efficiency step-dow n regulators. Tw o regulators pro-
vide up to 00ma of output current and the other tw o
regulators produce up to 400ma. All four regulators
are 2.25M Hz, constant-frequency, current mode
sw itching regulators that can be independently con-
trolled through I
2
C. All regulators are internally com-
pensated eliminating the need for external compensa-
tion components.
The LTC35 2 offers tw o different types of adjustable
step-dow n regulators. The tw o Type A regulators
(R 00A, R400A) can have the feedback voltage ad-
justed from 425mv to 800mv in 25mv increments. The
tw o Type B regulators (R 00B, R400B) can have the
DC
1 1 2 3
Q U ICK S TA R T G U IDE
L T C3 5 6 2
L in e a r U S B B a tte ry Ch a rg e r w ith Du a B u c k R e g u a to rs

DC1123 QUICK START GUIDE
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output voltages adjusted through I
2
C control from
00mv to 3.775V in 25mv increments.
Q U ICK STA RT PROCEDU RE
Using short tw isted pair leads for any pow er connec-
tions and w ith all loads and pow er supplies off, refer
to Figure 1 for the proper measurement and equip-
ment setup.
NOTE. W hen measuring the input or output voltage ripple, care must be
taken to avoid a long ground lead on the oscilloscope probe. M easure the
input or output voltage ripple by touching the probe tip directly across the
VCC or VOUT and GND terminals. See Figure 2 for proper scope probe
technique.
1. Place jumpers and load settings in the follow ing posi-
tions:
JP1 ( UN600A) = ON
JP2 ( UN400A) = ON
Load 1 = Consant Current 50mA
Load 2 = Constant Current 50mA
Load 3 = Constant Current 50mA
Load 4 = Constant Current 50mA
2. Connect Pow er Supply PS1 to VIN terminals and ad-
just to 4.5 Volts to the demo board, as show n in Fig-
ure 1.
3. Verify that OUT 00A (1.8V) and O UT400A (1.5V) are
operational w ith proper output voltages.
4. Once the proper output voltages are established, ad-
just the loads w ithin the operating range and observe
the output voltage regulation, ripple voltage, and effi-
ciency.
5. Open the Quickstart Softw are as discribed in the
DC590 Quick Start Guide
6. Set Jumpers JP1 (RUN400A) and JP2 (RU N 00A) to
Off Position. Connect Ribbon cable from DC590 demo
circuit to J2. The LTC 35 2 demonstation softw are
should pop-up automatically w hen the cable is in-
stalled.
7. Using the LTC35 2 softw are GUI. See Figure 3. Set all
modes to Burst mode, VOUT 00A to 1.82V, VOUT
00B to 3.3V, VO UT 400A to 1.51V and VO UT 400B to
1.2V. Set all loads to 50mA. Check Auto Update but-
tons. Click on Enable All button.
8. Once the proper output voltages are established, ad-
just the loads w ithin the operating range and observe
the output voltage regulation, ripple voltage, and effi-
ciency.
9. Using the LTC35 2 softw are GUI. Set all modes to
Pulse Skip mode, VOUT 00A to 1.82V, VOUT 00B to
3.3V, VOUT 400A to 1.51V and VO UT 400B to 1.2V.
Set all loads to 50mA.
10. Once the proper output voltages are established, ad-
just the loads w ithin the operating range and observe
the output voltage regulation, ripple voltage, and effi-
ciency.
11. Using the LTC35 2 softw are GUI. Set all modes to
Forced Burst mode, VOU T 00A to 1.82V, VOUT 00B
to 3.3V, VOUT 400A to 1.51V and VOUT 400B to 1.2V.
Set all loads to 50mA.
12. Once the proper output voltages are established, ad-
just the loads w ithin the operating range and observe
the output voltage regulation, ripple voltage, and effi-
ciency
13. Using the LTC35 2 softw are GUI. Set all modes to
LDO mode, VO UT 00A to 1.82V, VOUT 00B to 3.3V,
VOUT 400A to 1.51V and VOUT 400B to 1.2V. Set all
loads to 50mA.
14. Once the proper output voltages are established, ad-
just the loads w ithin the operating range and observe
the output voltage regulation, ripple voltage, and effi-
ciency
15. Using the LTC35 2 softw are GUI. Set all modes to
Burst mode, VOUT 00A to 1.82V, VOU T 00B to
3.3V, VOUT 400A to 1.51V and VO UT 400B to 1.2V.
Set all loads to 50mA.
16. M onitor POR 00A pin w hile increasing Load1 until
the signal on POR 00A goes low . The voltage on
P 00A w ill be less than 92% of voltage setting.

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17. Set Load1 and Load2 to 450mA. Set Load3 and
Load4 to 300mA. Adjust PS1 over the operating range
and observe line regulation.
A PPL ICA TION INF ORM A TION
This demo circuit is designed to demonstrate the full
capability of the LTC35 2 I
2
C Quad Synchronous
Step-Dow n DC-DC Regulator. Not all components are
required in all applications. The critical circuit com-
ponents are on the top of the board near the IC and
listed in the R equired Circuit Components section of
the Bill of M aterials, in Figure 5.
The input capacitor netw ork of C1 and R1 is used to
dampen source lead inductances that commonly oc-
cur in laboratory setups w ith tw isted leads and a
bench pow er supply. W hen using a USB cable this
input damping netw ork w ill likely not be required.
Please note that the in-circuit capacitance of the
specified 10uF, 0805 ceramic capacitor for C1 and C2
is less than 5uF each w ith VIN greater than 4.25 Volts.
For good transient response and stability the output
capacitor each buck regulator should retain at least
4uF of capacitance over the operating temperature
and voltage range.
The output inductors for the OUT 00A and OUT 00B
are the recommended values of 3.3uH w hile the
OUT400A and OUT400B are 4.7uH.
Resistors R4 and R are to adjust the output voltage
seen on the OUT 00A output w hile R3 and R4 w ill set
the voltage on the OUT400A output.

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Figure 1. Proper M easurem ent Equipm ent Setup
VIN GND
Figure 2. M easuring Input or Output ipple

DC1123 QUICK START GUIDE
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Figure 3.
Figure 3. Graphical User Interface

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Figure 4. Circuit Schem atic

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Item Qty Reference - Des Part Description Manufacturer, Part #
REQUIRED CIRCUIT COMPONENTS:
1 1 C2 CAP, CHIP X5R, 10uF, 10V, 0805 Murata, GRM21BR61A106KE19
2 4 C4,C7,C8,C9 CAP, CHIP,X5R, 10uF, 6.3V, 0603 TDK, C1608X5R0J106M
3 2 C5,C6 CAP, CHIP, COG, 10pF, 50v, 0402 Murata, GRM1557U1H100JZ01D
4 2 L2,L4 INDUCTOR, 3.3uH, 0.120 Ohms, 1.0A TOKO, 1098AS-3R3M
5 2 L1,L3 INDUCTOR, 4.7uH, 0.155 Ohms, 0.88A TOKO, 1098AS-4R7M
6 1 R3 RES, 0402, 475K OHMS, 1%, 1/16w VISHAY, CRCW0402475KFKED
7 1 R4 RES, 0402, 634K OHMS, 1%, 1/16w VISHAY, CRCW402634KFKED
8 1 R5 RES, 0402, 536K OHMS, 1%, 1/16w VISHAY, CRCW402536KFKED
9 1 R6 RES, 0402, 499K OHMS, 1%, 1/16w VISHAY, CRCW0402499KFKED
10 2 R12,R13 RES, 0402, 3.3M OHMS, 5%, 1/16w VISHAY, CRCW04023M30JNED
11 1 U1 I
2
C QUAD SYNCHRONOUS STEP-DOWN
DC/DC REGULATOR LINEAR TECH, LTC3562EUD
ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS:
1 2 C10,C11 CAP, CHIP, X5R, 0.1uF, 10V TDK, C1005X5R1A104K
2 1 C1 CAP, CHIP,X5R, 10uF, 10V TDK, C2012X5R0J106M
3 1 R7 RES, 0402, 0.0 Ohms, 1/16w VISHAY, CRCW04020000Z0ED
4 1 R2 RES, 0402, 100K Ohms, 5%, 1/16w VISHAY, CRCW0402100KJNED
5 4 R8,R9,R10,R11 RES, 0402, 5.1K OHMS, 5%, 1/16w VISHAY, CRCW04025K1JNED
6 1 R1 RES, 0402, 1 OHM, 5%, 1/16w VISHAY, CRCW04021R00JNED
7 1 U2 SERIAL EEPROM MICROCHIP, 24LC025-I/ST
HARDWARE FOR DEMO BOARD ONLY:
1 2 JP1,JP2 HEADER,3 PINS, 2mm SAMTEC, TMM-103-02-L-S
2 2 JP1,JP2 SHUNT, 2mm SAMTEC, 2SN-BK-G
3 1 J1 CONN, USB MINI-B TYCO, 1734035-2
4 1 J2 HEADER, 2X7 PIN, 0.079CC MOLEX/WALDEN, 87831-1420
5 10
E1,E5,E6,E7,E8,
E9,E15,E16,E17,
E18
TURRET, 0.09 DIA MILL-MAX, 2501-2
6 8 E2,E3,E4,E10,E11,
E12,E13,E14 TURRET, 0.061 DIA MILL-MAX, 2308-2
7 4 STAND-OFF, NYLON 0.25" tall (SNAP ON) KEYSTONE, 8831 (SNAP ON)
Figure 5. Bill of M aterials