L6235 datasheet(8/25 Pages) STMICROELECTRONICS

8 / 25 page

L6235

8/25

CIRCUIT DESCRIPTION

POWER STAGES and CHARGE PUMP

The L6235 integrates a Three-Phase Bridge, which

consists of 6 Power MOSFETs connected as shown

on the Block Diagram. Each Power MOS has an

RDS(ON) = 0.3Ω (typical value @25°C) with intrinsic

fast freewheeling diode. Switching patterns are gen-

erated by the PWM Current Controller and the Hall

Effect Sensor Decoding Logic (see relative para-

graphs). Cross conduction protection is implemented

by using a dead time (tDT = 1µs typical value) set by

internal timing circuit between the turn off and turn on

of two Power MOSFETs in one leg of a bridge.

Pins VSA and VSB MUST be connected together to

the supply voltage (VS).

Using N-Channel Power MOS for the upper transis-

tors in the bridge requires a gate drive voltage above

the power supply voltage. The Bootstrapped Supply

(VBOOT) is obtained through an internal oscillator and

few external components to realize a charge pump

circuit as shown in Figure 3. The oscillator output (pin

VCP) is a square wave at 600KHz (typically) with 10V

amplitude. Recommended values/part numbers for

the charge pump circuit are shown in Table1.

Table 1. Charge Pump External Component

Values.

Figure 3. Charge Pump Circuit

LOGIC INPUTS

Pins FWD/REV, BRAKE, EN, H1, H2 and H3 are TTL/

CMOS and µC compatible logic inputs. The internal

structure is shown in Figure 4. Typical value for turn-

ON and turn-OFF thresholds are respectively Vth(ON)

= 1.8V and Vth(OFF) = 1.3V.

Pin EN (enable) may be used to implement Overcurrent

and Thermal protection by connecting it to the open col-

lector DIAG output If the protection and an external dis-

able function are both desired, the appropriate

connection must be implemented. When the external

signal is from an open collector output, the circuit in Fig-

ure 5 can be used . For external circuits that are push

pull outputs the circuit in Figure 6 could be used. The re-

sistor REN should be chosen in the range from 2.2KΩ to

180K

Ω. Recommended values for REN and CEN are re-

spectively 100K

Ω and 5.6nF. More information for se-

lecting the values can be found in the Overcurrent

Protection section.

Figure 4. Logic Input Internal Structure

Figure 5. Pin EN Open Collector Driving

Figure 6. Pin EN Push-Pull Driving

CBOOT

220nF

10nF

100

Ω

1N4148

CBOOT

VSA

VCP

VBOOT

VSB

D01IN1328

D01IN1329

ESD

PROTECTION

OPEN

COLLECTOR

OUTPUT

REN

CEN

DIAG

D02IN1378

ESD

PROTECTION

PUSH-PULL

OUTPUT

REN

CEN

D02IN1379

DIAG

ESD

PROTECTION

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