STPD01 datasheet(17/43 Pages) STMICROELECTRONICS

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Operation description

7.1

Enable

The device can be forced into shutdown mode by pulling the enable pin low. In this condition, the I2C interface is

switched off.

Once the EN pin voltage exceeds the threshold value, then the device immediately switches on following the

start-up sequence.

7.1.1

Digital enable

The device can be enabled/disabled using the external pin EN, which switches off the DC-DC, the oscillator and

the digital core completely.

Optionally, the DC-DC can be switched off by the DIG_EN bit in I2C register (0x06), but in this case the digital

core is kept partially ON to allow the I2C to wake up the device.

Table 7. Functional modes

Dig_EN bit

EN pin

I2C interface

DC-DC state

Pon

Low

OFF

Stop

Functional

Low

High

Functional

Stop

Functional

High

Functional

Operating

Functional

7.2

Cable drop compensation

In some applications, the output voltage needs to be increased proportionally to load current to compensate the

potential voltage drop across copper tracks (and output cable). The compensation acts by altering the current

flowing in the high-side of the voltage feedback resistor divider. The resulting compensation voltage is expressed

as follows:

ΔVout=k⋅ILOAD⋅RSENSE⋅ RCDC1/RCDC2

(1)

where the parameter k is 18 and RCDC2 depends on the cable resistance, with RCDC1 being typically 10 kOhm.

The cable drop compensation loop should be very slow to avoid potential disturbance to the voltage loop. This

can be achieved by a proper choice of RCDC1 and CCDC.

STPD01

Operation description

DS13473 - Rev 1

page 17/43

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