L6258EX datasheet(13/32 Pages) STMICROELECTRONICS

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L6258EX

Functional description

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2.3

Phase input ( PH )

The logic level applied to this input determines the direction of the current flowing in the

winding of the motor.

High level on the phase input causes the motor current flowing from OUT_A to OUT_B

through the load.

2.4

Triangular generator

This circuit generates the two triangular waves TRI_0 and TRI_180 internally used to

generate the duty cycle variation of the signals driving the output stage in bridge

configuration.

The frequency of the triangular wave defines the switching frequency of the output, and can

be adjusted by changing the capacitor connected at TR1_CAP pin:

where: K = 1.5 x 10-5

2.5

Charge pump circuit

To ensure the correct driving of the high side drivers a voltage higher than Vs is supplied on

the Vboot pin. This boostrap voltage is not needed for the low side power DMOS transistors

because their sources terminals are grounded. To produce this voltage a charge pump

method is used. It is made by using two external capacitors; one connected to the internal

oscillator (CP) and the other (Cboot) to storage the overvoltage needed for the driving the

gates of the high side DMOS. The value suggested for the capacitors are:

LHL

88.9

92.1

95.2

98.4

100

Table 5.

Current levels (continued)

Current level

% of IMAX

ref

----

Table 6.

Charge pump capacitor's values

Component name

Component's function

Value

Unit

Cboot

Storage capacitor

100

Pump capacitor

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