LTC3785_15 Datasheet, PDF (1/20 Pages) Linear Technology – 10V, High Efficiency, Synchronous, No RSENSE Buck-Boost Controller

Features
n _{Single Inductor Architecture Allows VIN Above,}
Below or Equal to V_OUT
n _{2.7V to 10V Input and Output Range}
n _{Up to 96% Efficiency}
n _{Up to 10A of Output Current}
n _{All N-channel MOSFETs, No RSENSE™}
n _{True Output Disconnect During Shutdown}
n _{Programmable Current Limit and Soft-Start}
n _{Optional Short-Circuit Shutdown Timer}
n _{Output Overvoltage and Undervoltage Protection}
n _{Programmable Frequency: 100kHz to 1MHz}
n _{Selectable Burst Mode}^® _Operation
n _{Available in 24-Lead (4mm × 4mm) Exposed Pad}
QFN Package
Applications
n _{Palmtop Computers}
n _{Handheld Instruments}
n _{Wireless Modems}
n _{Cellular Telephones}
LTC3785
10V, High Efficiency,
Synchronous, No R_SENSE
Buck-Boost Controller
Description
The LTC^®3785 is a high power synchronous buck-boost
controller that drives all N-channel power MOSFETs from
input voltages above, below and equal to the output volt-
age. With an input range of 2.7V to 10V, the LTC3785 is
well suited for a wide variety of single or dual cell Li-Ion
or multicell alkaline/NiMH applications.
The operating frequency can be programmed from
100kHz to 1MHz. The soft-start time and current limit are
also programmable. The soft-start capacitor doubles as
the fault timer which can program the IC to latch off or
recycle after a determined off time. Burst Mode opera-
tion is user controlled and can be enabled by driving the
MODE pin high.
Protection features include foldback current limit, short-
circuit and overvoltage protection.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. No R_SENSE is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Typical Application
V_OUT
V_IN
V_CC
205k
I_SVIN
1.3k
270pF
V_SENSE
205k 121k
TG1
V_BST1
FB
SW1
121k 12k
I_SSW1
V_DRV
1nF
BG1
LTC3785
V_C
59k
RT
I_SVOUT
MODE
TG2
4.7µF
0.22µF
V_IN
2.7V
TO 10V
22µF
4.7µH
V_OUT
3.3V
5A
V_BST2
RUN/SS
SW2
42.2k ^ILSET
I_SSW2
1nF
CCM
BG2
GND
0.22µF
100µF
3785 TA01a
Efficiency vs Input Voltage
100
V_OUT = 3.3V
F_OSC = 500kHz
95
I_LOAD = 2A
I_LOAD = 1A
90
85
2.5
4
5.5
7
8.5
10
V_IN (V)
3785 TA01b
3785fc