SRK2000 datasheet(10/19 Pages) STMICROELECTRONICS

10 / 19 page

Application information

SRK2000

10/19

DocID17811 Rev 4

As VCC exceeds VCCOn, the internal current sink IEN is switched off and the enable function

is activated. The voltage on the pin is then compared to an internal reference VEN_On set at

1.8 V: if this threshold is exceeded the gate drivers GD1 and GD2 are enabled and the SR

MOSFET is operated; otherwise, the device stays in an idle condition and the SR MOSFET

in the off state.

Using the pull-up resistor RP, the voltage on the EN pin rises as IEN is switched off and tends

to VCC, therefore exceeding VEN_On and enabling the operation of both SR MOSFETs.

Essentially, this results in enabling the gate-driving as VCC exceeds VCCOn and disabling it

as VCC falls below VCCOn. This configuration is thereby recommended when SR MOSFETs

are logic level types.

6.1.2

Resistor divider configuration

To enable gate-driving with a VCC voltage higher than a predefined value VCC_G, to properly

drive a standard SR MOSFET, the EN pin is biased by a resistor divider (R1 upper resistor,

R2 lower resistor) whose value is chosen so as to exceed VEN_On when VCC = VCC_G and

also to set the desired VDVS1,2_Off level. Note that, with a falling VCC, gate-driving is

disabled at a VCC level about 2.5% lower than VCC_G, because of the 45 mV hysteresis of

the comparator.

The equations that describe the circuit in the two crucial conditions VCC = VCCOn (when the

decision of the VDVS1,2_Off level is made) and VCC = VCC_G (when gate-driving is to be

enabled) are respectively:

Figure 6. EN pin biased with a resistor divider to program the gate drive UVLO

threshold VCC_G

Equation 3



















CCOn

SRK2000 Datasheet(PDF) 10 Page - STMicroelectronics