Linear LTC3562, DC1123 User Manual
DC1123 QUICK START GUIDE
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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 l B u c k R e g u la to rs
DESCRIPTION
Demonstration circuit 1123 is a Linear USB Battery
Charger w ith Dual Buck R egulators featuring the
LTC3562. The LTC3562 is a quad high efficiency monolithic synchronous step-dow n regulator w ith an I2C interface. 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 voltages can be programmed betw een 600mV and 3.775V in
25mV steps (Type B). All four regulators operate independently and can be put into pulse skip, LDO, Burst
M ode operation or forced Burst M ode operation through
I2C control. The Type A regulators have separate R UN
pins that can be enabled if I2C 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
sw itched into LDO, Burst M ode operation or forced Burst
M ode operation, extending battery life in portable systems. The quiescent current drops to under 100µA w ith
all regulators in LDO mode and under 0.1µA w hen all
regulators are shut down
Sw itching frequency is internally set to 2.25M Hz, allow ing the use of small surface mount inductors and capacitors. All regulators are internally compensated.
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 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: VCC
P600A 0.96V to 1.82V, 600mA (M ax)
2.85V to 5.5V (Subject to dropout)
P600B 1.20V to 3.775V, 600mA (M ax)
P400A 0.80V to 1.51V, 400mA (M ax)
P400B 0.60V to 3.775V, 400mA (M ax)
OPERA TING PRINCIPL ES
The LTC3562 is a highly integrated power management
IC that contains four I2C controllable, monolithic, high
efficiency step-dow n regulators. Tw o regulators provide up to 600ma 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 controlled through I2C. All regulators are internally com-
pensated eliminating the need for external compensation components.
The LTC3562 offers tw o different types of adjustable
step-dow n regulators. The tw o Type A regulators
(R600A, R 400A) can have the feedback voltage adjusted from 425mv to 800mv in 25mv increments. The
tw o Type B regulators (R 600B, R400B) can have the
DC1123 QUICK START GUIDE
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output voltages adjusted through I2C control from
600mv to 3.775V in 25mv increments.
Q U ICK STA RT PROCEDU RE
Using short tw isted pair leads for any pow er connections and w ith all loads and pow er supplies off, refer
to Figure 1 for the proper measurement and equipment 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 VO U T and GND terminals. See Figure 2 for proper scope probe
technique.
1. Place jumpers and load settings in the following posi-
tions:
JP1 (R U N600A)
JP2 (R U N400A)
Load 1
Load 2
Load 3
Load 4
2. Connect Pow er Supply PS1 to VIN terminals and ad-
just to 4.5 Volts to the demo board, as show n in Figure 1.
3. Verify that OU T600A (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 efficiency.
5. Open the Quickstart Softw are as discribed in the
DC590 Q uick Start Guide
= Consant Current 50mA
= Constant Current 50mA
= Constant Current 50mA
= Constant Current 50mA
= ON
= ON
1.2V. Set all loads to 50mA. Check Auto U pdate buttons. 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 efficiency.
9. Using the LTC3562 softw are GU I. Set all modes to
Pulse Skip mode, VO UT 600A to 1.82V, VOU T 600B to
3.3V, VO UT 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 efficiency.
11. Using the LTC3562 softw are G UI. Set all modes to
Forced Burst mode, VO UT 600A to 1.82V, VOU T 600B
to 3.3V, VOU T 400A to 1.51V and VOU T 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 efficiency
13. Using the LTC3562 softw are G UI. Set all modes to
LDO mode, VO U T 600A to 1.82V, VO UT 600B to 3.3V,
VO UT 400A to 1.51V and VOU T 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 efficiency
6. Set Jumpers JP1 (R UN 400A) and JP2 (RU N600A) to
Off Position. Connect Ribbon cable from DC590 demo
circuit to J2. The LTC 3562 demonstation softw are
should pop-up automatically w hen the cable is installed.
7. Using the LTC3562 softw are G UI. See Figure 3. Set all
modes to Burst mode, VO UT 600A to 1.82V, VOU T
600B to 3.3V, VOU T 400A to 1.51V and VOU T 400B to
15. Using the LTC3562 softw are G UI. Set all modes to
Burst mode, VOU T 600A to 1.82V, VO UT 600B to
3.3V, VO UT 400A to 1.51V and VO UT 400B to 1.2V.
Set all loads to 50mA.
16. M onitor PO R600A pin w hile increasing Load1 until
the signal on POR 600A goes low . The voltage on
P600A w ill be less than 92% of voltage setting.
DC1123 QUICK START GUIDE
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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 LTC3562 I2C Quad Synchronous
Step-Dow n DC-DC R egulator. 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 R equired Circuit Components section of
the Bill of M aterials, in Figure 5.
The input capacitor netw ork of C1 and R 1 is used to
dampen source lead inductances that commonly occur 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 OU T600A and OUT600B
are the recommended values of 3.3uH w hile the
OU T400A and O U T400B are 4.7uH.
Resistors R 4 and R 6 are to adjust the output voltage
seen on the OU T600A output w hile R3 and R 4 w ill set
the voltage on the OU T400A output.
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