LTC3711 Datasheet, PDF (1/24 Pages) Linear Technology – 5-Bit Adjustable, Wide Operating Range, No RSENSE

LTC3711
5-Bit Adjustable,
Wide Operating Range,
No R_SENSE^TM Step-Down Controller
FEATURES
s _{5-Bit Programmable Output Voltage: 0.925V to 2V}
s _{No Sense Resistor Required}
s _{True Current Mode Control}
s _{2% to 90% Duty Cycle at 200kHz}
s _{tON(MIN) < 100ns}
s _{Supports Active Voltage Positioning}
s _{Extremely Fast Transient Response}
s _{Stable with Ceramic COUT}
s _{Dual N-Channel MOSFET Synchronous Drive}
s _{Power Good Output Voltage Monitor}
s _{Wide VIN Range: 4V to 36V}
s _{±1% 0.8V Reference}
s _{Adjustable Current Limit}
s _{Adjustable Switching Frequency}
s _{Programmable Soft-Start}
s _{Output Overvoltage Protection}
s _{Optional Short-Circuit Shutdown Timer}
s _{Micropower Shutdown: IQ < 30µA}
s _{Available in 24-Lead Narrow SSOP Package}
U
APPLICATIO S
s _{Power Supplies for Mobile Pentium}^® _Processors
s _{Notebook and Palmtop Computers, PDAs}
DESCRIPTIO
The LTC^®3711 is a synchronous step-down switching
regulator controller for CPU power. An output voltage
between 0.925V and 2.000V is selected by a 5-bit code
(Intel mobile VID specification). The controller uses a
valley current control architecture to deliver very low duty
cycles without requiring a sense resistor. Operating fre-
quency is selected by an external resistor and is compen-
sated for variations in V_IN and V_OUT.
Discontinuous mode operation provides high efficiency
operation at light loads. A forced continuous control pin
reduces noise and RF interference and can assist second-
ary winding regulation by disabling discontinuous mode
operation when the main output is lightly loaded.
Fault protection is provided by internal foldback current
limiting, an output overvoltage comparator and optional
short-circuit shutdown timer. Soft-start capability for sup-
ply sequencing is accomplished using an external timing
capacitor. The regulator current limit level is user pro-
grammable. Wide supply range allows operation from 4V
to 36V at the input.
, LTC and LT are registered trademarks of Linear Technology Corporation.
No R_SENSE is a trademark of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corporation.
TYPICAL APPLICATIO
C_SS
0.1µF
C_C 500pF
R_C 20k
5-BIT VID
PGOOD I_ON
V_IN
RUN/SS TG
I_TH
SW
SGND BOOST
LTC3711
INTV_CC
VID4
BG
VID3
VID2 _PGND
VID1
VID0 V_OSENSE
R_ON
330k
C_B 0.33µF
D_B
CMDSH-3
+
C_VCC
4.7µF
M1
IRF7811A
M2
IRF7811A
×2
V_IN
C_IN
5V TO 24V
L1
1µH
22µF
50V
×3
V_OUT
1.5V
+ ^{COUT 15A}
270µF
2V
×4
D1
UPS840
C_IN: UNITED CHEMICON
THCR70EIH226ZT
C_OUT: CORNELL DUBILIER
ESRE271M02B
L1: SUMIDA CEP125-IROMC
3711 F01a
Figure 1. High Efficiency Step-Down Converter
Efficiency vs Load Current
100
V_OUT = 1.5V
EXTV_CC = 5V
90
V_IN = 5V
V_IN = 15V
80
70
60
0.01
0.1
1
LOAD CURRENT (A)
10
3711 F01b
3711f
1