iru3034 International Rectifier Corp., iru3034 Datasheet - Page 3

• Manufacturer Part Number: iru3034
• Description: 8-pin Pwm Switcher Controller Ic With Current Limiting -
• Manufacturer: International Rectifier Corp.

PIN DESCRIPTIONS
PIN # PIN SYMBOL
BLOCK DIAGRAM
1
2
3
4
5
6
7
8
Gnd
Drv
1
5
V
CS+
Gnd
CS-
Drv
V
SS
V
HYST
FB
12
V
2
12
The PWM output of the switching controller. This pin is a totem pole drive that is con-
nected to the gate of the power MOSFET. A resistor may be placed from this pin to the
gate in order to reduce switching noise.
This pin supplies the voltage to the PWM drive and hysteresis circuitry and it is connected
to the 12V supply. A 1 F, high frequency capacitor must be connected from this pin to
ground to provide the peak current for charging and discharging of the MOSFET.
A resistor divider from this pin to the output of the switching regulator and ground sets the
Core supply voltage.
A resistor and a 10pF capacitor is connected from this pin to the V
ripple voltage for the switching regulator.
This pin is connected to the IC substrate and must be connected to the lowest potential in
the system.
This pin is connected to the minus side of the external current sense resistor. An internal
current source together with an external resistor in series with this pin programs the
current limit threshold voltage. This voltage divided by the external current sense resistor
sets the current limit threshold.
This pin is connected to the plus side of the external current sense resistor. A resistor in
series with this pin and a capacitor connected between this pin and pin 6 provides a high
frequency filtering for the noise spikes of turn on and turn off switching.
This pin provides the soft-start for the regulator during power up. It also sets a long off time
when the converter goes into current limiting, providing low duty cycle for the catch diode
allowing it to survive during short circuit.
PIN DESCRIPTION
V
HYST
4
Figure 2 - Simplified block diagram of the IRU3034.
PWM Control
S.S. / Hiccup
UVLO
Control
www.irf.com
V
3
FB
1.25V
R
3R
5V Reg
V
REF
20uA
IRU3034 & (PbF)
FB
pin to set the output
CS+
CS-
SS
6
7
8
3