STOD03AS datasheet(19/25 Pages) STMICROELECTRONICS

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STOD03AS

Detailed description

8.1.5

Enable pin

The device operates when the EN pin is set high. If the EN pin is set low, the device stops

switching, and all the internal blocks are turned off. In this condition the current drawn from

VINP/VINA is below 1 µA in the whole temperature range. In addition, the internal switches

are in an OFF state so the load is electrically disconnected from the input, this avoids

unwanted current leakage from the input to the load.

When the EN is pulled high, the P1B switch is turned on for 100 µs. In normal operation,

during this time, apart of a small drop due to parasitic resistance, VMID reaches VIN.

If, after this 100 µs, VMID stays below VIN, the P1B is turned off and stays off until a new

pulse is applied to the EN. This mechanism avoids the STOD03AS starting if a short-circuit

is present on VMID.

8.1.6

Soft-start and inrush current limiting

After the EN pin is pulled high, or after a suitable voltage is applied to VINP, VINA and EN, the

device initiates the startup phase.

As a first step, the CMID capacitor is charged and the P1B switch implements a current

limiting technique in order to keep the charge current below 400 mA. This avoids the battery

overloading during startup.

After VMID reaches the VINP voltage level, the P1B switch is fully turned on and the soft-start

procedure for the step-up is started. After around 2 ms the soft-start for the inverting is

started. The positive and negative voltages are under regulation at around 6 ms after the

EN pin is asserted high.

8.1.7

Undervoltage lockout

The undervoltage lockout function avoids improper operation of the STOD03AS when the

input voltage is not high enough. When the input voltage is below the UVLO threshold the

device is in shutdown mode. The hysteresis of 50mV avoids unstable operation when the

input voltage is close to the UVLO threshold.

8.1.8

Overtemperature protection

An internal temperature sensor continuously monitors the IC junction temperature. If the IC

temperature exceeds 140 °C, typical, the device stops operating. As soon as the

temperature falls below 125 °C, typical, normal operation is restored.

8.1.9

Short-circuit protection

When short-circuit occurs, the device is able to detect the voltage difference between VIN

and VMID. Overshoots on LX1 are limited, decreasing the inductor current. After that, the

output stages of the device are turned off. This status is maintained, avoiding current flowing

to the load. A new ENABLE transition is needed to restart the device. During startup the

short-circuit protection is active.

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