Linear Technology DC1123 User manual

DC1123A QUICK START GUIDE
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DESCRIPTION
Demonstration circuit 1123 is a I
2
C Quad Synchro-
nous Step-Down DC/DC Regulators featuring the
LTC3562. The LTC3562 is a quad high efficiency
monolithic synchronous step-down regulator with
an I
2
C interface. Two regulators are externally ad-
justable and can have their feedback voltages pro-
grammed between 425mV and 800mV in 25mV
(Type A). The other two regulators are fixed output
regulators whose output voltages can be pro-
grammed between 600mV and 3.775V in 25mV
steps (Type B). All four regulators operate inde-
pendently and can be put into pulse skip, LDO,
Burst Mode operation or forced Burst Mode opera-
tion 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-
3562 ideally suited for single Li-ion battery pow-
ered applications. At low output load conditions,
the regulators can be switched into LDO, Burst
Mode operation or forced Burst Mode operation,
extending battery life in portable systems. The qui-
escent current drops to under 100µA with all regu-
lators in LDO mode and under 0.1µA when all
regulators are shut down
Switching frequency is internally set to 2.25MHz,
allowing the use of small surface mount inductors
and capacitors. All regulators are internally com-
pensated.
The LTC3562 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 Mode, are registered trademarks of Linear Technology
Corporation.
All other trademarks are the property of their respective owners.
TABLE 1. Typical Specifications (25°C)
Input Voltage Range: V
CC
2.85V to 5.5V (Subject to dropout)
P600A 0.96V to 1.82V, 600mA (Max)
P600B 1.20V to 3.775V, 600mA (Max)
P400A 0.80V to 1.51V, 400mA (Max)
P400B 0.60V to 3.775V, 400mA (Max)
OPERATING PRINCIPLES
The LTC3562 is a highly integrated power man-
agement IC that contains four I
2
C controllable,
monolithic, high efficiency step-down regulators.
Two regulators provide up to 600ma of output
current and the other two regulators produce up
to 400ma. All four regulators are 2.25MHz, con-
stant-frequency, current mode switching regula-
tors that can be independently controlled through
I
2
C. All regulators are internally compensated
DC1123
QUICK START GUIDE
LTC3562
I
2
C Quad Synchronous
Step
-
Down DC/DC Regulators

DC1123A QUICK START GUIDE
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eliminating the need for external compensation
components.
The LTC3562 offers two different types of ad-
justable step-down regulators. The two Type A
regulators (R600A, R400A) can have the feed-
back voltage adjusted from 425mv to 800mv in
25mv increments. The two Type B regulators
(R600B, R400B) can have the output voltages
adjusted through I
2
C control from 600mv to
3.775V in 25mv increments.
QUICK START PROCEDURE
Using short twisted pair leads for any power
connections and with all loads and power sup-
plies off, refer to Figure 1 for the proper meas-
urement and equipment setup.
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 VCC or VOUT and GND terminals. See
Figure 2 for proper scope probe technique.
1. Place jumpers and load settings in the following
positions:
JP1 (RUN600A) = ON
JP2 (RUN400A) = ON
Load 1 = Consant Current 50mA
Load 2 = Constant Current 50mA
Load 3 = Constant Current 50mA
Load 4 = Constant Current 50mA
2. Connect Power Supply PS1 to VIN terminals
and adjust to 4.5 Volts to the demo board, as
shown in Figure 1.
3. Verify that OUT600A (1.8V) and OUT400A
(1.5V) are operational with proper output volt-
ages.
4. Once the proper output voltages are estab-
lished, adjust the loads within the operating
range and observe the output voltage regula-
tion, ripple voltage, and efficiency.
5. Open the Quickstart Software as discribed in the
DC590 Quick Start Guide
6. Set Jumpers JP1 (RUN400A) and JP2
(RUN600A) to Off Position. Connect Ribbon ca-
ble from DC590 demo circuit to J2. The LTC
3562 demonstation software should pop-up
automatically when the cable is installed.
7. Using the LTC3562 software GUI. See Figure 3.
Set all modes to Burst mode, VOUT 600A to
1.82V, VOUT 600B to 3.3V, VOUT 400A to
1.51V and VOUT 400B to 1.2V. Set all loads to
50mA. Check Auto Update buttons. Click on
Enable All button.
8. Once the proper output voltages are estab-
lished, adjust the loads within the operating
range and observe the output voltage regula-
tion, ripple voltage, and efficiency.
9. Using the LTC3562 software GUI. Set all modes
to Pulse Skip mode, VOUT 600A to 1.82V,
VOUT 600B to 3.3V, VOUT 400A to 1.51V and
VOUT 400B to 1.2V. Set all loads to 50mA.
10. Once the proper output voltages are estab-
lished, adjust the loads within the operating
range and observe the output voltage regula-
tion, ripple voltage, and efficiency.
11. Using the LTC3562 software GUI. Set all mod-
es to Forced Burst mode, VOUT 600A to 1.82V,
VOUT 600B 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 estab-
lished, adjust the loads within the operating
range and observe the output voltage regula-
tion, ripple voltage, and efficiency
13. Using the LTC3562 software GUI. Set all mod-
es to LDO mode, VOUT 600A to 1.82V, VOUT
600B to 3.3V, VOUT 400A to 1.51V and VOUT
400B to 1.2V. Set all loads to 50mA.

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14. Once the proper output voltages are estab-
lished, adjust the loads within the operating
range and observe the output voltage regula-
tion, ripple voltage, and efficiency
15. Using the LTC3562 software GUI. Set all
modes to Burst mode, VOUT 600A to 1.82V,
VOUT 600B to 3.3V, VOUT 400A to 1.51V and
VOUT 400B to 1.2V. Set all loads to 50mA.
16. Monitor POR600A pin while increasing Load1
until the signal on POR600A goes low. The volt-
age on P600A will be less than 92% of voltage
setting.
17. Set Load1 and Load2 to 450mA. Set Load3
and Load4 to 300mA. Adjust PS1 over the oper-
ating range and observe line regulation.
APPLICATION INFORMATION
This demo circuit is designed to demonstrate
the full capability of the LTC3562 I
2
C Quad Syn-
chronous Step-Down DC-DC Regulator. Not all
components are required in all applications.
The critical circuit components are on the top of
the board near the IC and listed in the Required
Circuit Components section of the Bill of Materi-
als, in Figure 5.
The input capacitor network of C1 and R1 is
used to dampen source lead inductances that
commonly occur in laboratory setups with
twisted leads and a bench power supply. When
using a USB cable this input damping network
will 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 with VIN greater than 4.25 Volts.
For good transient response and stability the
output capacitor each buck regulator should re-
tain at least 4uF of capacitance over the operat-
ing temperature and voltage range.
The output inductors for the OUT600A and
OUT600B are the recommended values of
3.3uH while the OUT400A and OUT400B are
4.7uH.
Resistors R4 and R6 are to adjust the output
voltage seen on the OUT600A output while R3
and R4 will set the voltage on the OUT400A
output.

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Figure 1. Proper Measurement Equipment Setup
VIN GND
Figure 2. Measuring Input or Output Ripple

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Figure 3.
Figure 3. Graphical User Interface

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Figure 4. Circuit Schematic

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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, GRM1555C1H100JZ01D
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 Materials

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DC1123A