LED5000 datasheet(11/52 Pages) STMICROELECTRONICS

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LED5000

Functional description

Doc ID 023951 Rev 1

11/51

4.1

Power supply and voltage reference

The internal regulator circuit consists of a startup circuit, an internal voltage pre-regulator,

the bandgap voltage reference and the bias block that provides current to all the blocks. The

starter supplies the startup current to the entire device when the input voltage goes high and

the device is enabled (inhibit pin connected to ground). The pre-regulator block supplies the

bandgap cell with a pre-regulated voltage that has a very low supply voltage noise

sensitivity.

4.2

Voltage monitor

An internal block continuously senses the Vcc, Vref and Vbg. If the monitored voltages are

good, the regulator begins operating. There is also a hysteresis on the Vcc(UVLO).

Figure 4.

Internal circuit

4.3

Soft-start

The startup phase is implemented ramping the reference of the embedded error amplifier in

1 msec typ. time. It minimizes the inrush current and decreases the stress of the power

components at power up.

Figure 5.

Soft-start open

AM13488v1

AM13489v1

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