LTC1708-PG Datasheet, PDF (1/32 Pages) Linear Technology – Dual Adjustable 5-Bit VID High Efficiency, 2-Phase Current Mode Synchronous Buck Regulator Controller

Final Electrical Specifications
LTC1708-PG
Dual Adjustable 5-Bit VID
High Efficiency, 2-Phase Current Mode
Synchronous Buck Regulator Controller
FEATURES
DESCRIPTIO
February 2000
s _{Out-of-Phase Controllers Reduce Input Capacitance}
and Power Supply Induced Noise
s _OPTI-LOOP^TM _{Compensation Minimizes COUT}
s _{Power Good Output Monitors Both Outputs}
s _{5-Bit Mobile VID Control, VOUT: 0.9V to 2.0V}
s _{Dual N-Channel MOSFET Synchronous Drive}
s _{±1% Output Voltage Accuracy}
s _{DC Programmed Fixed Frequency 150kHz to 300kHz}
s _{Wide VIN Range: 3.5V to 36V Operation}
s _{Very Low Dropout Operation: 99% Duty Cycle}
s _{Adjustable Soft-Start Current Ramping}
s _{Foldback Output Current Limiting}
s _{Latched Short-Circuit Shutdown with Defeat Option}
s _{Output Overvoltage Protection}
s _{Remote Output Voltage Sense}
s _{Low Shutdown Current: 20µA}
s _{5V and 3.3V Standby Regulators}
s _{Selectable Constant Frequency, Burst Mode}^TM _and
Continuous Operation
U
APPLICATIO S
s _{Notebook and Palmtop Computers, PDAs}
s _{Portable Instruments}
The LTC^®1708 is a dual adjustable 5-bit VID program-
mable step-down switching regulator controller that drives
all N-Channel power MOSFET stages. A constant fre-
quency current mode architecture allows adjustment of
the frequency up to 300kHz. Power loss and noise due to
the ESR of the input capacitance are minimized by oper-
ating the two main controller output stages out of phase.
OPTI-LOOP compensation allows the transient response
to be optimized over a wide range of output capacitance
and ESR values. The precision 0.8V reference is compat-
ible with future microprocessor generations, and a wide
3.5V to 30V (36V maximum) input supply range that
encompasses all battery chemistries. A power good out-
put indicates when the output voltages are within 7.5% of
their programmed value.
A RUN/SS pin for each controller provides both soft-start
and an optional timed, short-circuit shutdown. Other
protection features include: internal foldback current lim-
iting and an output overvoltage crowbar. The force con-
tinuous control pin (FCB) can be used to inhibit Burst
Mode operation or to regulate a third, flyback output.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode and OPTI-LOOP are trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
M1
L1
1µH
D1
M2
V_OUT1
0.925V TO
2.00V
14.1A
R_SENSE1
0.003Ω
C_{OUT1a +}
10µF
6.3V
CERAMIC
C_OUT1
270µF
2V
SP
×4
+
4.7µF
C_B1 0.47µF
D3
V_IN
TG1
VIDV_CC INTV_CC
TG2
BOOST1
BOOST2
SW1
SW2
LTC1708-PG
BG1
BG2
5 VID BITS
1000pF
C_C1
1500pF
R_C1
22k
VID0 TO VID4
PGND
SENSE1⁺
SENSE2⁺
SENSE1^–
PGOOD
SENSE2^–
ATTNIN
V_OSENSE2
I_TH1
I_TH2
RUN/SS1 SGND RUN/SS2
C_SS1
0.1µF
C_SS2
0.1µF
1µF
D4
CERAMIC
M3a
C_B2 0.1µF
M3b
C_IN
10µF
50V
CERAMIC
×4 _L2
2.2µH
V_IN
4.75V TO 28V
D2
1000pF
C_C2
220pF
R3
R_C2
15k
20k
1%
R_SENSE2
0.01Ω
R4
63.4k
1%
C_OUT
180µF
4V
SP
V_OUT2
1.5V
4A
M1: IRF7811
M2: 1RF7809
M3a, M3b: FDS6982
L1: VISHAY 5050CE
ATTNOUT CONNECTED TO EAIN1
1628 F01
Figure 1. High Efficiency VID Controlled, 2-Output Step-Down Converter
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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