DC1123 QUICK START GUIDE
1
DESCRIPTION
Demonstration circuit 1123 is a Linear U SB Battery
Charger w ith Dual Buck Regulators featuring the
LTC3562. The LTC3562 is a quad high efficiency mono-
lithic synchronous step-down regulator w ith an I
2
C inter-
face. Tw o regulators a re externally adjustable and can
have their feedback voltages programmed betw een
425mV and 800mV in 25mV (Type A). The other two
regulators are fixed output regulators whose output volt-
ages can be programmed between 600mV and 3.775V in
25mV steps (Type B). All four regulators operate inde-
pendently and can be put into pulse skip, LDO , B urst
M ode operation or forced Burst M ode operation through
I
2
C control. The Type A regulators have separate R UN
pins that can be enabled if I
2
C control is unavailable.
The 2.85V to 5.5V input range makes the LTC-3562 ide-
ally suited for single Li-ion battery pow ered applications.
At low output load conditions, the regulators can be
switched 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 when all
regulators are shut down
Sw itching frequency is internally set to 2.25M H z, allow-
ing the use of small surface mount inductors and capaci-
tors. 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 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 (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 I
2
C controllable, monolithic, high
efficiency step-dow n regulators. Tw o regulators pro-
vide up to 600ma of output current and the other two
regulators produce up to 400ma. All four regulators
are 2.25M H z, constant-frequency, current mode
switching regulators that can be independently con-
trolled through I
2
C. A ll regulators are internally com-
pensated eliminating the need for external compensa-
tion components.
The LTC3562 offers two different types of adjustable
step-down regulators. The two Type A regulators
(R600A, R 400A) can have the feedback voltage ad-
justed from 425mv to 800mv in 25mv increments. The
two Type B regulators (R600B, R400B) can have the