TAS5101

SLES039 – JUNE 2002

5

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functional description

PWM H-bridge state control

The digital interface control signals consists of PWM_AP, PWM_AM, PWM_BP, and PWM_BM. These signals

are a complementary differential signal format for the A-side H-bridge and the B-side H-bridge.

bootstrapped gate drive

The TAS5101 includes 2 dedicated bootstrapped power supplies. A bootstrap capacitor is connected between

the individual bootstrap pin and the associated output as described in the application note SLAA117. For

example, a capacitor will be connected between the BOOTSTRAPA pin and OUTPUTA pin, and another

capacitor will be connected between the BOOTSTRAPB pin and the OUTPUTB pin. The bootstrap power

supply minimizes the number of high voltage power supply levels externally supplied to the system while

providing a low noise supply level for driving the high-side N-channel DMOS transistors. See application note

SLAA117 for details.

low-dropout voltage regulator

Two on-chip low-dropout voltage regulators (LDO) are provided to minimize the number of external power

supplies needed for the system. These voltage regulators are for internal circuits only and cannot be used for

external circuitry. Each LDO is dedicated to an H-bridge and its gate driver. An LDO output capacitor is

connected between the individual LDO output pin and the associated output return as described in the

application note SLAA117. For example, a capacitor will be connected between the LDROUTA pin and PVSS

pin, and another capacitor will be connected between the LDROUTB pin and PVSS pin. This capacitor is usually

0.1

µF.

high-current H-bridge output stage

The positive outputs of the H-bridge are the two OUTPUTA pins. The negative outputs of the H-bridge are the

two OUTPUTB pins. The logic for the input command to H-bridge outputs is described in the H-bridge output

mapping section below. When the TAS5101 is in the normal mode, as seen in the H-bridge output mapping

tables, the outputs are decoded from the inputs. However, the TAS5101 is immediately shut down if any of the

following error conditions occur: over-current, over-temperature, low regulator output voltage, or an illegal PWM

input state is applied. For these conditions, the outputs are set to the appropriate disabled state as specified

in the H-bridge output mapping section, and the SHUTDOWN pin is set low.

H-bridge output mapping

The A-side and B-side H-bridge output is designed to the following truth table:

INPUTS

OUTPUTS

DESCRIPTION

RESET

HiZ

PWM_AP/BP

PWM_AM/BM

SHUTDOWN

OUTPUTA/B

DESCRIPTION

X

X

X

X

0

0 or Hi-Z†

Shutdown

X

0

X

X

1

Hi-Z

High Impedance

0

1

X

X

1

0

Low

1

1

0

0

0

0

Low

1

1

0

1

1

0

Normal

1

1

1

0

1

1

Normal

1

1

1

1

0

0

Low

† Output is 0 for low voltage, over temperature, and illegal input. Hi-Z is for over current.