L9780 datasheet(20/56 Pages) STMICROELECTRONICS

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Main functionalities

L9780

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DocID026356 Rev 3

In the table above the list of selectable Cint is shown and for each Cint is specified maximum

and minimum Rtot value that guarantee respectively a phase margin > 60° and a bandwidth

> 100 kHz.

In order to avoid that during the activation of VCCS for a short time the output current can be

out of control, the selection or the change of different functionalities of VCCS (like the

change of output channel, of input clamp or of Cint capacitances) are possible only when

VCCS is disabled. Well defined rules have to be respected in order to be able to drive

correctly VCCS; these rules are specified in Section 5.5.2.

All VCCS electrical parameters ranges are specified in sections Table 12 and Table 15. All

the logic signals used to select VCCS functionalities are defined in detail in section 7.3.

4.10

Pin PG1, PG2, SR functionalities

The device is able to drive via SPI (through bits PG1EN, PG2EN) the gate of the external

protection FET, that can be connected to PG1 or PG2 pin. This external FET acts as a

switch that connects to ground the second terminal of the pump cell and completes the path

for VCCS output current (see block diagram in Figure 2). In this condition SR pin voltage is

expected to be low; if the voltage value exceeds STBS1 threshold (typical value of 200mV

and possible range specified in Table 13), a sensor short to battery condition is detected.

For the consequences of this detection see Section 5.1.

In order to avoid the possibility that the external FET switch on when the device is

un-powered the FET driver has 100 k

 (typ) pull down resistor permanently connected to

PG1 and PG2 pins. Electrical parameters of PG driver are specified in Table 12 and

Table 15.

318

212

324

216

329

219

335

223

341

227

347

231

352

235

357

238

363

242

369

246

374

249

380

253

386

257

Table 6. Cint vs. possible Rtot to guarantee phase margin and bandwidth (continued)

Cint (pF)

Maximum Rtot [Ω] value to

guarantee a phase margin > 60°

Minimum Rtot [Ω] value to

guarantee a bandwidth > 100 kHz

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