4

Rev. 1.0

09/09/02

IRU3047

www.irf.com

Figure 2 - Block diagram of the IRU3047.

PIN#

PIN SYMBOL

PIN DESCRIPTION

9,12

10

11

15

16

17

19

20

LDrv2, LDrv1

PGnd

Fb3

SS

PGood

Gnd

Output driver for the synchronous power MOSFET.

This pin serves as the separate ground for MOSFET’s driver and should be connected to

the system’s ground plane.

Supply voltage for the low side output drivers.

Driver signal for the LDO’s external transistor.

LDO’s feedback pin, connected to a resistor divider to set the output voltage of LDO.

Soft-Start pin. The converter can be shutdown by pulling this pin below 0.5V.

Power Good pin. This pin is a collector output that switches Low when any of the outputs

are outside of the specified under voltage trip point.

Ground pin.

Bias

Generator

LDrv2

Two Phase

Oscillator

1.25V

3V

Ramp1

Fb3

0.5V

POR

POR

Gnd

HDrv2

VcH2

SS

Comp2

1.25V

Error Amp2

PWM Comp2

POR

25uA

Reset Dom

LDrv1

HDrv1

VcH1

Fb1

Comp1

Error Amp1

PWM Comp1

25K

Reset Dom

Set1

Set2

Ramp2

64uA Max

UVLO

VcH2

3.5V / 3.3V

VcH1

3.5V / 3.3V

4.2V / 4.0V

Fb2

40mA LDO Controller

PGnd

Vcc

1.25V

1.25V

SS > 2V

Vp2

PGood

Fb3

Fb2

Fb1

PGood

Fb2 Monitor

Shut Down

R

S

Q

S

R

Q

Vcc

4

17

18

5

1

2

3

6

16

20

14

13

11

12

7

8

9

19

10

15

2V

SS

25K

25K

25K

25K

25K

BLOCK DIAGRAM