TDA7572 datasheet(46/64 Pages) STMICROELECTRONICS

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Step-up

TDA7572

46/64

Step-up

A current boost controller is provided to allow high power operation in the 14V automotive

environment. This is a clocked PWM, current mode control block that drives an external

NFET. Following is present the application circuits.

Figure 10.

Step-up application diagram

In the Step-up implemented is present a current control loop and a voltage one to fix the

output voltage. On the pin BSTVSense is reported the voltage VSP except for the gain of

Step-up, here imposed by the ratio R1 and R2. To improve stability, response time and

inductor requirements, an inner current control loop has been implemented. The inductor

parasitic resistance will be an adequate current sensor, and it is expected that with an RC

could be cancelled the zero of the boost inductor. Instead of use the parasitic resistor of

inductor a series sensing resistor could be used. The current sensing is take out by the pins

V14Sense and Csense.

To avoid destructive startup currents, soft startup is provided which functions by increasing

the allowed current limit using 4 steps roughly 4ms apart.

An overcurrent condition is declared if there is an extended period of high current.

Excessive current is detected (by monitoring the voltage across Csense and V14Sense

pins) for a period exceeding 20ms, which are considered to be caused by a fault condition,

are detected as Csense exceeding a voltage threshold and are handled by forcing a restart

of the soft start sequence when over-current is declared. Following are reported the

threshold of current limiting.

14V

VSM

Step-Up

Regulator

VSM

+14V

VSP

V14Sense

BSTGate

BSTSource

BSTVSense

Coil

CSense

AC00022

TDA7572 Datasheet(PDF) 46 Page - STMicroelectronics