LTC3716 Datasheet, PDF (1/28 Pages) Linear Technology – 2-Phase, 5-Bit VID, Current Mode, High Efficiency, Synchronous Step-Down Switching Regulator

LTC3716
2-Phase, 5-Bit VID,
Current Mode, High Efficiency,
Synchronous Step-Down
Switching Regulator
FEATURES
s _{Output Stages Operate Antiphase Reducing Input}
and Output Capacitance Requirements and Power
Supply Induced Noise
s _{Dual Input Supply Capability for Load Sharing}
s _{5-Bit Mobile VID Code: VOUT = 0.6V to 1.75V}
s _{±1% Output Voltage Accuracy}
s _{True Remote Sensing Differential Amplifier}
s _{Power Good Output Voltage Monitor}
s _{Supports Active Voltage Positioning}
s _{Current Mode Control Ensures Current Sharing}
s _OPTI-LOOP^TM _{Compensation Minimizes COUT}
s _{Three Operational Modes: PWM, Burst and Cycle Skip}
s _{Programmable Fixed Frequency: 150kHz to 300kHz}
s _{Wide VIN Range: 4V to 36V Operation}
s _{Adjustable Soft-Start Current Ramping}
s _{Internal Current Foldback and Short-Circuit Shutdown}
s _{Overvoltage Soft Latch Eliminates Nuisance Trips}
s _{Available in 36-Lead Narrow SSOP Package}
U
APPLICATIO S
s _{Mobile Computer CPU Supply}
, LTC and LT are registered trademarks of Linear Technology Corporation.
OPTI-LOOP and Burst Mode are trademarks of Linear Technology Corporation.
DESCRIPTIO
The LTC^®3716 is a 2-phase, VID programmable, synchro-
nous step-down switching regulator controller that drives
two N-channel external power MOSFET stages in a fixed fre-
quency architecture. The 2-phase controller drives its two
output stages out of phase at frequencies up to 300kHz to
minimize the RMS ripple currents in both input and output
capacitors. The 2-phase technique effectively multiplies the
fundamental frequency by two, improving transient re-
sponse while operating each channel at an optimum fre-
quency for efficiency. Thermal design is also simplified.
An operating mode select pin (FCB) can be used to regu-
late a secondary winding or select among three modes
including Burst Mode^TM operation for highest efficiency. An
internal differential amplifier provides true remote sensing
of the regulated supply’s positive and negative output ter-
minals as required in high current applications.
The RUN/SS pin provides soft-start and optional timed,
short-circuit shutdown. Current foldback limits MOSFET
dissipation during short-circuit conditions when the
overcurrent latchoff is disabled. OPTI-LOOP compensation
allows the transient response to be optimized for a wide
range of output capacitors and ESR values.
TYPICAL APPLICATIO
0.1µF
220pF
3.3k
5 VID BITS
FCB
V_IN
TG1
RUN/SS
BOOST1
SW1
LTC3716
I_TH
BG1
SGND
PGND
PGOOD
VID0–VID4
SENSE1⁺
SENSE1^–
TG2
EAIN
BOOST2
ATTENOUT
SW2
ATTENIN
BG2
V_DIFFOUT
V_OS–
V_OS+
INTV_CC
SENSE2⁺
SENSE2^–
0.47µF
0.47µF
10µF
10µF
35V
×4
1µH
D1
1 ^0.002Ω 2
3
4
V_IN
5V TO 28V
1µH
D2
1 ^0.002Ω 2
3
4
V_OUT
0.6V TO 1.75V
40A
+ ^COUT
1000µF
4V
×2
3716 F01
Figure 1. High Current Dual Phase Step-Down Converter
1