LTC1709-7 Datasheet, PDF (1/28 Pages) Linear Technology – 2-Phase, 5-Bit VID, Current Mode, High Efficiency, Synchronous Step-Down Switching Regulator

LTC1709-7
2-Phase, 5-Bit VID,
Current Mode, High Efficiency,
Synchronous Step-Down Switching Regulator
FEATURES
DESCRIPTIO
s _{Output Stages Operate Antiphase Reducing Input}
Capacitance Requirements and Power Supply
Induced Noise
s _{Dual Input Supply Capability for Load Sharing}
s _{5-Bit Mobile VID Code: VOUT = 0.925V to 2V}
s _{Current Mode Control Ensures Current Sharing}
s _{True Remote Sensing Differential Amplifier}
s _{Power Good Output Indicator}
s _OPTI-LOOP^TM _{Compensation Minimizes COUT}
s _{Three Operational Modes: PWM, Burst and Cycle Skip}
s _{Programmable Fixed Frequency: 150kHz to 300kHz}
s _{±1% Output Voltage Accuracy}
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 _{Active Voltage Positioning Capable}
s _{Available in 36-Lead Narrow SSOP Package}
U
APPLICATIO S
s _{Mobile/Desktop Computers}
s _{Internet Servers}
s _{Large Memory Arrays}
s _{DC Power Distribution Systems}
The LTC^®1709-7 is a 2-phase, VID programmable, synchro-
nous step-down switching regulator controller that drives
two all N-channel external power MOSFET stages in a fixed
frequency 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
OPTI-LOOP and Burst Mode are trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
0.1µF
220pF
3.3k
5 VID BITS
FCB
V_IN
TG1
RUN/SS
BOOST1
SW1
LTC1709-7
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
0.002Ω
0.002Ω
1µH
Figure 1. High Current Dual Phase Step-Down Converter
V_IN
5V TO 28V
V_OUT
0.925V TO 2V
40A
+ ^COUT
1000µF
4V
×2
170989 F01
1