SiP41109/41110

Vishay Siliconix

New Product

www.vishay.com

6

Document Number: 73023

S-51104—Rev. A, 13-Jun-05

droop allowed in the bootstrapped supply voltage when the

high-side MOSFET is driven high. The bootstrap capacitor

value is typically 0.1 mF to 1 mF. The bootstrap capacitor

transient spikes and ringing.

Shoot-Through Protection

The external MOSFETs are prevented from conducting at the

same time during transitions. Break-before-make circuits

monitor the voltages on the PHASE pin and the LGATE pin and

control the switching as follows: When the signal on PWM goes

low, UGATE will go low after an internal propagation delay.

After the voltage on PHASE falls below 2.5 V by the inductor

action, the low-side driver is enabled and LGATE goes high

after some delay. When the signal on PWM goes high, LGATE

will go low after an internal propagation delay. After the voltage

on LGATE drops below 2.5 V the high-side driver is enabled

and UGATE will go high after an internal propagation delay. If

PHASE does not drop below 2.5 V within 380 ns after UGATE

goes low, LGATE is forced high until the next PWM transition.

MOSFET drivers draw large peak currents from the supplies

when they switch. A local bypass capacitor is required to

supply this current and reduce power supply noise. Connect

a 1-mF ceramic capacitor as close as practical between the

Undervoltage Lockout

Undervoltage lockout prevents control of the circuit until the

supply voltages reach valid operating levels. The UVLO circuit

specified voltage. A separate UVLO forces UGATE low when

the voltage between BOOT and PHASE is below the specified

voltage.

Thermal Protection

If the die temperature rises above 165_C, the thermal

protection disables the drivers. The drivers are re-enabled

after the die temperature has decreased below 140_C.

TYPICAL CHARACTERISTICS

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15

25

35

45

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65

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85

95

105

0

1234

5

1 MHz

500 kHz

200 kHz

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10

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90

100

0

1234

5

1 MHz

500 kHz

200 kHz