IRU3138 Datasheet, PDF (1/18 Pages) International Rectifier – SYNCHRONOUS PWM CONTROLLER FOR TERMINATION POWER SUPPLY APPLICATIONS

Data Sheet No. PD94701
IRU3138
SYNCHRONOUS PWM CONTROLLER
FOR TERMINATION POWER SUPPLY APPLICATIONS
FEATURES
1A Peak Output Drive Capability
0.8V Precision Reference Voltage Available
Shuts off both drivers at shorted output
and shutdown
200KHz to 400KHz operation set by an external
resistor
Soft-Start Function
Uncommitted Error Amplifier available for DDR
voltage tracking application
Protects the output when control FET is shorted
Synchronous Controller in 14-Pin Package
APPLICATIONS
DDR memory source sink Vtt application
Graphic Card
Low cost on-board DC to DC such as
5V to 3.3V, 2.5V or 1.8V
DESCRIPTION
The IRU3138 controller IC is designed to provide a low
cost synchronous Buck regulator for voltage tracking
applications such DDR memory and general purpose
on-board DC to DC converter. Modern micro processors
combined with DDR memory, need high-speed bandwidth
data bus which requires a particular bus termination volt-
age. This voltage will be tightly regulated to track the
half of chipset voltage for best performance. The IRU3138
together with two N-channel MOSFETs, provide a low
cost solution for such applications. This device features
a programmable frequency set from 200KHz to 400KHz,
under-voltage lockout for both Vcc and Vc supplies, an
external programmable soft-start function as well as
output under-voltage detection that latches off the de-
vice when an output short is detected.
TYPICAL APPLICATION
VDDQ
(2.5V)
DDR
Memory
C1
0.1uF
R1
1K
R2
1K _C5
0.1uF
C7
3300pF
R3
13K
Vcc
VR E F
VP
Vc
HDrv
SS/SD _U1
IRU3138
Rt
Comp
LDrv
PGnd
Fb
Gnd
12V
C2
1uF
L1
1uH
C3
2x 47uF
D1
BAT54
Q1
IRF7460
Q2
IRF7456
L2
3.3uH
5V
C4
47uF
Vtt
1.25V @ 10A
C6
2x 150uF
40m V
Figure 1 - Typical application of IRU3138 when VTT tracks the VDDQ.
PACKAGE ORDER INFORMATION
TA (°C)
0 To 70
DEVICE
IRU3138CS
PACKAGE
14-Pin Plastic SOIC NB (S)
Rev. 1.0
01/29/04
www.irf.com
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