iru3138 International Rectifier Corp., iru3138 Datasheet - Page 3

• Manufacturer Part Number: iru3138
• Description: Synchronous Pwm Controller For Termination Power Supply Applications -
• Manufacturer: International Rectifier Corp.

PARAMETER
Error Amp
Fb Voltage Input Bias Current
Fb Voltage Input Bias Current
V
Transconductance
Output Drivers
Rise Time
Fall Time
Dead Band Time
Max Duty Cycle
Min Duty Cycle
Note 1: Guaranteed by design, but not tested in production.
PIN DESCRIPTIONS
PIN#
Rev. 1.0
01/29/04
P
14
10
12
13
11
1
2
3
4
5
6
7
8
9
Voltage Range
PIN SYMBOL
SS / SD
Comp
PGnd
HDrv
V
LDrv
Gnd
V
NC
Fb
V
V
Rt
REF
CC
P
C
This pin is connected directly to the output of the switching regulator via resistor divider to
provide feedback to the Error amplifier.
Non-inverting input of error amplifier.
Reference Voltage.
This pin provides biasing for the internal blocks of the IC as well as power for the low side
driver. A minimum of 1mF, high frequency capacitor must be connected from this pin to
ground to provide peak drive current capability.
No Connection.
Output driver for the synchronous power MOSFET.
Analog ground for internal reference and control circuitry. Connect to PGnd with a short
trace.
This pin serves as the separate ground for MOSFET's drivers and should be connected to
system's ground plane. A high frequency capacitor (0.1mF to 1mF) must be connected
from V
Output driver for the high side power MOSFET. This pin should not go negative (below
ground), this may cause problem for the gate drive circuit. It can happen when the inductor
current goes negative (Source/Sink), soft-start at no load and for the fast load transient
from full load to no load. To prevent negative voltage at gate drive, a low forward voltage
drop diode might be connected between this pin and ground.
This pin is connected to a voltage that must be at least 4V higher than the bus voltage of
the switcher (assuming 5V threshold MOSFET) and powers the high side output driver. A
minimum of 1mF, high frequency capacitor must be connected from this pin to ground to
provide peak drive current capability.
The switching frequency can be Programmed between 200KHz and 400KHz by connect-
ing a resistor between Rt and Gnd. Floating the pin set the switching frequency to 200KHz
and grounding the pin set the switching frequency to 400KHz.
Compensation pin of the error amplifier. An external resistor and capacitor network is
typically connected from this pin to ground to provide loop compensation.
This pin provides soft-start for the switching regulator. An internal current source charges
an external capacitor that is connected from this pin to ground which ramps up the output
of the switching regulator, preventing it from overshooting as well as limiting the input
current. The converter can be shutdown by pulling this pin below 2.8V.
PIN DESCRIPTION
CC
SYM
and V
Toff
GM
T
Ton
I
I
FB1
FB2
Tr
T
DB
f
C
SS=3V, Fb=1V
SS=0V, Fb=1V
C
C
Fb=0.7V, Freq=200KHz
Fb=1.5V
pins to this pin for noise free operation.
LOAD
LOAD
=3000pF
=3000pF
TEST CONDITION
www.irf.com
MIN
500
0.7
85
TYP
800
100
0.1
50
35
35
90
MAX
1000
1.5
70
70
IRU3138
0
UNITS
mmho
mA
mA
ns
ns
ns
%
%
V
3