Data sheet

8

Rev. 1.0, 2009-05-18

TLE8366

Buck Regulator

An internal temperature sensor detects the temperature of the device, it will be switched off if the junction

temperature exceeds 175 °C.

The error Flip flop is set by the Schmitt Trigger 1 and will be reset by one of these signals. This will close the NOR1

gate and shutdown the pulse. The bootstrap capacitor monitoring is connected directly to the NOR1 gate.

The bootstrap under-voltage shutdown is created by the BDS UV comparator, which compares the bootstrap

capacitor voltage to a reference level. If the bootstrap capacitor voltage is too low, the pulse will be shut down.

PWM pulses are passing through the NOR 1 gate. In case if one of the mentioned failures will occur this gate will

be closed and the pulse switched immediately off.

The PWM Flip-Flop is set by NAND2, which combines the clock from the Schmitt Trigger 1 with the output from

NOR1. The PWM Flip-Flop is reset by the output of the NOR1.

5.1.1.3

Internal Power Stage

The gate driver consists of the Gate driver itself, an inverter for the PWM signal and the gate driver supply. The

gate Driver Supply is connected over pin BDS to the BDS capacitor. A charge pump is integrated to support the

gate drive in cases of low input voltage, small differential voltage between input supply and output voltage and

during start up. To minimize emissions the charge pump is switched off if the input voltage is high enough to charge

the bootstrap capacitor.

5.1.2

Operation Mode

The PWM pulses are voltage controlled. The error amplifier and the PWM comparator are creating the PWM

pulses using the oscillator saw-tooth signal and the feedback voltage. The pulse-width modulation is done so that

the feedback voltage (at pin FB for the adjustable version) is similar to the reference voltage (0.6 V).

Between input voltages from 8.0 to 36 V the integrated feed forward path provides a fast line transient rejection.

(feed-forward means sensing the input voltage and react on fluctuations before they influence the output)

To achieve a stable output voltage even under low duty cycle conditions (light load down to zero output load and/or

high input voltage) a pulse skipping mode is implemented. Pulse skipping is also used for operation with low supply

voltages leading to duty cycles > 92%.