L6208 Просмотр технического описания (PDF) - STMicroelectronics

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L6208

DMOS driver for bipolar stepper motor

STMicroelectronics 

Circuit description

5

Circuit description

L6208

5.1

Power stages and charge pump

The L6208 integrates two independent power MOS full bridges. Each power MOS has an

RDS(ON) = 0.3  (typical value at 25 °C), with intrinsic fast freewheeling diode. Switching

patterns are generated by the PWM current controller and the phase sequence generator

(see Section 6: PWM current control). Cross conduction protection is achieved using

a deadtime (tDT = 1 s typical value) between the switch off and switch on of two Power

MOSFETs in one leg of a bridge.

Pins VSA and VSB MUST be connected together to the supply voltage VS. The device

operates with a supply voltage in the range from 8 V to 52 V. It has to be noticed that the

RDS(ON) increases of some percents when the supply voltage is in the range from 8 V to 12 V

(see Figure 38: Typical low-side RDS(ON) vs. supply voltage on page 29 and Figure 35:

Typical high-side RDS(ON) vs. supply voltage on page 29).

Using N-channel power MOS for the upper transistors in the bridge requires a gate drive

voltage above the power supply voltage. The bootstrapped supply voltage VBOOT is obtained

through an internal oscillator and few external components to realize a charge pump circuit

as shown in Figure 8. The oscillator output (VCP) is a square wave at 600 KHz (typical) with

10 V amplitude. Recommended values/part numbers for the charge pump circuit are shown

in Table 6.

Table 6. Charge pump external components values

Component

Value

CBOOT

CP

RP

D1

D2

220 nF

10 nF

100 

1N4148

1N4148

Figure 8. Charge pump circuit

VS

D1

D2

CBOOT

RP

CP

VCP VBOOT

VSA VSB D01IN1328

12/35

DocID7514 Rev 2

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