SiP41109/41110

Vishay Siliconix

New Product

Document Number: 73023

S-51104—Rev. A, 13-Jun-05

www.vishay.com

5

FUNCTIONAL BLOCK DIAGRAM

Figure 1.

PWM

GND

UGATE

PHASE

LGATE

BOOT

(2.5 V)

−

+

UVLO

OTP

Tri-State

Detect

+8-V Linear

Regulator

Linear

Regulator

+5 V

UVLO

DETAILED OPERATION

PWM/Tri-State Enable

The PWM pin controls the switching of the external MOSFETs.

The driver logic operates in a noninverting configuration. The

PWM input stage should be driven by a signal with fast

transition times, like those provided by a PWM controller or

logic gate, (<200 ns). The PWM input functions as a logic input

and is not intended for applications where a slow changing

input voltage is used to generate a switching output when the

input switching threshold voltage is reached.

Shutdown

The SiP41109/41110 enters shutdown mode when the signal

driving PWM enters the tri-state window for more than 240 ns.

The shutdown state is removed when the PWM signal moves

outside the tri-state window. If the PWM is left open, the pin is

held to 2.5 V by an internal voltage divider, thus forcing the

tri-state condition.

Low-Side Driver

In the SiP41110, the low-side driver voltage is supplied by

High-Side Driver

The high-side driver is isolated from the substrate to create a

floating high-side driver so that an n-channel MOSFET can be

used for the high-side switch. The high-side driver voltage is

bootstrap capacitor, which is continually recharged by the

switching action of the output. During shutdown UGATE is

held low.

An integrated 80-mA, 8-V regulator supplies voltage to the

output is shorted to ground. A capacitor (1 mF minimum) must

Bootstrap Circuit

The internal bootstrap diode and an external bootstrap

capacitor supply voltage to the BOOT pin. An integrated

bootstrap diode replaces the external diode normally needed

for the bootstrap circuit; only a capacitor is necessary to

complete the bootstrap circuit. The bootstrap capacitor is

sized according to,