LTC1709-9_15 Datasheet, PDF (1/28 Pages) Linear Technology – 2-Phase, 5-Bit VID, Current Mode, High Efficiency, Synchronous Step-Down Switching Regulators

LTC1709-8/LTC1709-9
2-Phase, 5-Bit VID,
Current Mode, High Efficiency,
Synchronous Step-Down Switching Regulators
FEATURES
s _{Single Controller Operates Two Output Stages}
Antiphase Reducing Required Input Capacitance
and Power Supply Induced Noise
s _{Two 5-Bit Desktop VID Codes:}
LTC1709-8 For VRM8.4 (V_OUT from 1.3V to 3.5V)
LTC1709-9 For VRM9.0 (V_OUT from 1.1V to 1.85V)
s _{Current Mode Control Ensures Best Current Sharing}
s _{True Remote Sensing Differential Amplifier}
s _{Power Good Output Indicator}
s _OPTI-LOOP^TM _{Compensation Minimizes COUT}
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 _{Low Shutdown Current: 20µA}
s _{Available in 36-Lead Narrow SSOP Package}
U
APPLICATIO S
s _Workstations
s _{Internet Servers}
s _{Large Memory Arrays}
s _{DC Power Distribution Systems}
DESCRIPTIO
The LTC^®1709-8/LTC1709-9 are 2-phase, VID program-
mable, synchronous step-down switching regulator con-
trollers that drive 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 from 150kHz 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 response while
operating each channel at an optimum frequency for
efficiency. Thermal design is also simplified.
An internal differential amplifier provides true remote
sensing of the regulated supply’s positive and negative
output terminals as required for 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 compensa-
tion allows the transient response to be optimized for a
wide range of output capacitors and ESR values. The
LTC1709-8/LTC1709-9 implement two different VID
tables compliant with VRM8.4 and VRM9.0 respectively.
, LTC and LT are registered trademarks of Linear Technology Corporation.
OPTI-LOOP is a trademark of Linear Technology Corporation.
TYPICAL APPLICATION
0.1µF
220pF
3.3k
5 VID BITS
V_IN
TG1
RUN/SS
BOOST1
SW1
LTC1709-8
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 2-Phase Step-Down Converter
V_IN
5V TO 28V
V_OUT
1.3V TO 3.5V
40A
+ ^COUT
1000µF
4V
×2
17097 F01
1