LTC3737 Datasheet, PDF (1/24 Pages) Linear Technology – Dual 2-Phase, No RSENSE DC/DC Controller with Output Tracking

LTC3737
Dual 2-Phase, No R_SENSE^TM,
DC/DC Controller with
Output Tracking
FEATURES
s _{Sense Resistor Optional}
s _{Out-of-Phase Controllers Reduce Required}
Input Capacitance
s _{Programmable Output Voltage Tracking}
s _{Constant Frequency Current Mode Architecture}
s _{Wide VIN Range: 2.75V to 9.8V}
s _{Wide VOUT Range: 0.6V to VIN}
s _{0.6V ±1.5% Reference}
s _{Low Dropout Operation: 100% Duty Cycle}
s _{True PLL for Frequency Locking or Adjustment}
(Frequency Range 250kHz to 850kHz)
s _{Selectable Burst Mode}^® _{or Pulse Skipping Operation}
at Light Loads
s _{Internal Soft-Start Circuitry}
s _{Selectable Maximum Peak Current Sense Threshold}
s _{Power Good Output Voltage Monitor}
s _{Output Overvoltage Protection}
s _{Micropower Shutdown: IQ = 9µA}
s _{Tiny 4mm × 4mm QFN and 24-Lead SSOP Packages}
U
APPLICATIO S
s _{One or Two Lithium-Ion Powered Devices}
s _{Notebook and Palmtop Computers, PDAs}
s _{Portable Instruments}
s _{Distributed DC Power Systems}
DESCRIPTIO
The LTC^®3737 is a 2-phase dual step-down switching
regulator controller that requires few external compo-
nents. The constant frequency current mode architecture
provides excellent AC and DC load and line regulation.
MOSFET V_DS sensing eliminates the need for current
sense resistors and improves efficiency. Power loss and
noise due to the ESR of the input capacitance are mini-
mized by operating the two controllers out of phase.
Burst Mode operation provides high efficiency operation
at light loads. 100% duty cycle provides low dropout
operation and extends battery operating time.
Switching frequency can be programmed up to 750kHz,
allowing the use of small surface mount inductors and
capacitors. For noise sensitive applications, the LTC3737
can be externally synchronized from 250kHz to 850kHz.
Other features include a power good output voltage moni-
tor, a tracking input and internal soft-start.
The LTC3737 is available in the low profile thermally
enhanced (4mm × 4mm) QFN package or a 24-lead SSOP
narrow package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
No R_SENSE is a trademark of Linear Technology Corporation.
U.S. patent numbers 5481178, 5731694, 5929620, 6144194,6580258, 5994885
TYPICAL APPLICATIO
187k
59k
15k
220pF
220pF
15k
59k
118k
SW1
SENSE1⁺
V_FB1
PV_IN1
I_TH1
PGATE1
PGOOD
V_IN
LTC3737
SGND
PGND
TRACK
RUN/SS
I_TH2
V_FB2
SW2
PGATE2
PV_IN2
SENSE2⁺
V_IN
2.75V TO
M1
2.2µH
+
9.8V
V_OUT1
2.5V
D1
47µF
10µF
×2
D2
47µF
2.2µH
M2
3737 F01
V_OUT2
1.8V
Figure 1. High Efficiency, 2-Phase, 550kHz Dual Step-Down Converter
Efficiency vs Load Current
100
V_IN = 3.3V
95
90
V_OUT = 2.5V
85
V_OUT = 1.8V
80
75
70
65
60
55
50
1
10
100
1000
LOAD CURRENT (mA)
10000
3737 F01b
3737f
1