L6207 datasheet(10/53 Pages) STMICROELECTRONICS

10 / 53 page

AN1762 APPLICATION NOTE

10/53

Nevertheless, sensing resistor power rating should be chosen taking into account the peak value of the dissi-

pated power:

where Ipk is the peak value of the load current.

Using multiple resistors in parallel will help obtaining the required power rating with standard resistors, and re-

duce the inductance.

RSENSE tolerance reflects on the peak current error: 1% resistors should be preferred.

The following table shows RSENSE recommended values (to have 0.5V drop on it) and power ratings for typical

examples of current peak values.

3.6 Charge pump external components

An internal oscillator, with its output at

CP pin, switches from GND to 10V with a typical frequency of 600kHz

(see Figure 9).

Figure 9. Charge Pump.

When the oscillator output is at ground, C5 is charged by VS through D2. When it rises to 10V, D2 is reverse

biased and the charge flows from C5 to C8 through D1, so the VBOOT pin, after a few cycles, reaches the max-

imum voltage of VS + 10V - VD1 - VD2, which supplies the high-side gate drivers.

With a differential voltage between VS and VBOOT of about 9V and both the bridges switching at 50kHz, the typ-

ical current drawn by the VBOOT pin is 1.85 mA.

Ipk

RSENSE Value [Ω]

RSENSE Power Rating [W]

Alternatives

0.5

0.25

0.5

2 X 1

Ω, 0.25W paralleled

1.5

0.33

0.75

3 X 1

Ω, 0.25W paralleled

0.25

4 X 1

Ω, 0.25W paralleled

SEN SE

⋅

≈

L6205, L6206, L6207

VS + 10 V - VD1

VS -VD1

f = 600 kHz

VSA

VSB

VBOOT

RDS(ON) = 70

Ω

10 V

5 V

RDS(ON) = 70

Ω

To High-Side

Gate Drivers

10 V

f = 600 kHz

Charge Pump

Oscillator

VS + 10 V - VD1 - VD2

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