Datasheet

TPS51220A

SLUS897E –DECEMBER 2008–REVISED JANUARY 2013

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HIGH-SIDE DRIVER

The high-side driver is designed to drive high current, low R

DS(on)

N-channel MOSFET(s). The drive capability is

represented by its internal resistance, which is 1.7Ω for VBSTx to DRVHx, and 1Ω for DRVHx to SWx. When

configured as a floating driver, 5 V of bias voltage is delivered from VREG5 supply. The instantaneous drive

current is supplied by the flying capacitor between VBSTx and SWx pins. The average drive current is equal to

the gate charge at Vgs = 5V times switching frequency. This gate drive current as well as the low-side gate drive

current times 5 V makes the driving power which needs to be dissipated mainly from TPS51220A package. A

dead time to prevent shoot through is internally generated between high-side MOSFET off to low-side MOSFET

on, and low-side MOSFET off to high-side MOSFET on.

LOW-SIDE DRIVER

The low-side driver is designed to drive high-current low-R

DS(on)

N-channel MOSFET(s). The drive capability is

represented by its internal resistance, which are 1.3Ω for VREG5 to DRVLx and 0.7Ω for DRVLx to GND. The 5-

V bias voltage is delivered from VREG5 supply. The instantaneous drive current is supplied by an input capacitor

connected between VREG5 and GND. The average drive current is also calculated by the gate charge at

Vgs = 5 V times switching frequency.

CURRENT SENSING SCHEME

In order to provide both good accuracy and cost effective solution, the TPS51220A supports external resistor

sensing and inductor DCR sensing. An RC network with high quality X5R or X7R ceramic capacitor should be

used to extract voltage drop across DCR. 0.1μF is a good value to start the design. CSPx and CSNx should be

connected to positive and negative terminal of the sensing device respectively. TPS51220A has an internal

current amplifier. The gain of the current amplifier, Gc, is selected by TRIP terminal. In any setting, the output

signal of the current amplifier becomes 100mV at the OCL setting point. This means that the current sensing

amplifier normalize the current information signal based on the OCL setting. Attaching a RC network

recommended even with a resistor sensing scheme to get an accurate current sensing; see the external parts

selection session for detailed configurations.

Product Folder Links :TPS51220A