L5953

Functional description

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2.6

PWM step down voltage regulator

The switching regulator (

Figure 11.) inside the L5953 is a voltage control mode (also known

as a direct duty cycle) Buck regulator: the error signal coming from the error amplifier is

compared with a sawtooth to set on and off times of the power switch.

The feedforward control is introduced to get a quickly response to input voltage changes: the

sawtooth has a fixed frequency and an amplitude variable with the battery voltage.

Continuous mode operation is recommended in order to reduce the stress of the output

capacitor and of the free-wheeling diode.

2.6.1

Error amplifier and compensation network

The error amplifier (EA) is a voltage amplifier whose non-inverting input is fixed to the

reference voltage (1.275V bandgap voltage) and whose inverting input and output are

externally available for feedback and frequency compensation.