MC33253 查看數據表（PDF） - Motorola => Freescale

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MC33253

Full Bridge Pre-Driver

Motorola => Freescale 

MC33253

Driver Supply

The High Side Driver is supplied from the internal charge pump buffered at CP_OUT. The low-drop regulator provides

approx. 3.5 mA (fPWM = 50kHz) per gate. In case of the full bridge that means approximately. 14 mA; 7.0 mA for the high side and

7.0 mA for the low side. (Note: The average current required to switch a gate with a frequency of 100kHz is: Average Current

(Charge Pump) for PWM Frq. (fPWM) and ICP = Qg*fPWM = 75 nC*100 kHz = 7.5mA. A full bridge application switch only one high side

and one low side at the same time.)

External capacitors on Charge Pump and on Linear Regulator are necessary to supply high peak current absorbed during

switching. The Low Side Driver is supplied from built in low drop regulator.

Gate Protection

The low side gate is protected by the internal linear regulator, which guarantees that VGATE_LS does not exceed the maximum

VGS. Especially when working with the charge pump the voltage at POS_HS can be up to 65V. The high side gate is clamped

internally, in order to avoid a VGS exceeding 14V.

The Gate protection does not include a Flyback Voltage Clamp that protects the driver and the external FET from a Flyback

voltage that can appear when driving inductive load.This Flyback voltage can reach high negative voltage values and needs to

be clamped externally.

Figure 5. Gate Protection and Flyback Voltage Clamp

Vgs_ls

Vgs_hs

IN Output OUT

Driver

M1

GATE_HS

G_LOW

SRC_HS

G_LOW

IN Output OUT

Driver

Dcl

L1

M2

GATE_LS

VCC

VGS < 14 V

under all

conditions

Inductive

Flyback Voltage

Clamp

TMOS Failure Protection

All output driver stages are protected against TMOS failure conditions. If one of the external power FETs is destroyed (Gate

= VCC, or Gate = Gnd) the function of the remaining output driver stages is not affected. All output drivers are short circuit

protected against short circuits to ground.

Cross Conduction Suppression

The purpose of the cross conduction suppression is to avoid that high and low side FET are turned on at the same time,

which prevents the half bridge power FETs of a shoot-through condition. The CCS can be disabled / enabled by an external

signal (/CCS).

- /CCS=0, the cross conduction is not allowed.

- /CCS=1, the cross conduction is allowed.

MC33253

MOTOROLA

rev3.0 - 8/15

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