L6207 datasheet(11/53 Pages) STMICROELECTRONICS

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AN1762 APPLICATION NOTE

Resistor

R4 is added to reduce the maximum current in the external components and to reduce the slew rate of

the rising and falling edges of the voltage at the

CP pin, in order to minimize interferences with the rest of the

circuit. For the same reason care must be taken in realizing the PCB layout of

R4, C5, D1, D2 connections (see

also the

Layout Considerations section). Recommended values for the charge pump circuitry are:

D1, D2

: 1N4148

: 100

Ω (1/8 W)

: 10nF 100V ceramic

: 220nF 25V ceramic

Due to the high charge pump frequency, fast diodes are required. Connecting the cold side of the bulk capacitor

(C8) to VS instead of GND the average current in the external diodes during operation is less than 10 mA (with

R4 = 100

Ω); at startup (when VS is provided to the IC) is less than 200 mA while the reverse voltage is about

10 V in all conditions. 1N4148 diodes withstand about 200 mA DC (1 A peak), and the maximum reverse voltage

is 75 V, so they should fit for the majority of applications.

3.7 Sharing the Charge Pump Circuitry

If more than one device is used in the application, it's possible to use the charge pump from one L6205, L6206

or L6207 to supply the VBOOT pins of several ICs. The unused CP pins on the slaved devices are left uncon-

nected, as shown in Figure 10. A 100nF capacitor (C8) should be connected to the VBOOT pin of each device.

Supply voltage pins (VS) of the devices sharing the charge pump must be connected together.

The higher the number of devices sharing the same charge pump, the lower will be the differential voltage avail-

able for gate drive (VBOOT - VS), causing a higher RDS(ON) for the high side DMOS, so higher dissipating power.

In this case it's recommended to omit the resistor on the

CP pin, obtaining a higher current capability of the

charge pump circuitry.

Better performance can also be obtained using a 33nF capacitor for C5 and using schottky diodes (for example

BAT47 are recommended).

Sharing the same charge pump circuitry for more than 3÷4 devices is not recommended, since it will reduce the

VBOOT voltage increasing the high-side MOS on-resistance and thus power dissipation.

Figure 10. Sharing the charge pump circuitry.

VSA

VSB

VBOOT

C18 = 100 nF

To High-Side

Gate Drivers

VSA

VSB

VBOOT

C8 = 100nF

To High-Side

Gate Drivers

To other Devices

L6205, L6206, L6207

D1 = BAT47

D2 = BAT47

C5 = 33nF

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