Obsolete

Product(s)

- Obsolete

Product(s)

DC Motor Driver operation

L8229

38/42

10

DC Motor Driver operation

When in L8229_0 or L8229_1 configuration, the device could be configured to drive two

different DC motors. Each drive provides bi-directional drive to a DC motor via the serial

control and the PWM pins. The W0 bits 8 and 14 in the register will control the direction of

drive while the PWM input pin controls the switching of the drivers. According to above

description, the motor drive will be in voltage mode only.

The device could also drive a single DC motor with increased current by paralleling the two

bridges. If this is required, W0 bit 15 must be set to 1 and OUT1A must be shorted to

OUT2A while OUT1B must be shorted to OUT2B. In this case of two bridges paralled to

drive a single DC motor, the W0 bit 14 (PHASE2) will not be used as well as pin 17 (PWM2).

This means that the device will act as a single bridge with ouputs OUTA (OUT1A in parallel

with OUT2A), OUTB (OUT1B in parallel with OUT2B) and driven by PHASE1 (W0 bit 8) and

PWM1 (pin 20).

The drives are powered by VS.

The crossover delay is controlled to provide sufficient time for cross-conduction

suppression, so that at no time both the upper and lower output devices on the same side of

the H bridge are allowed to conduct simultaneously.

A blanking period following a current turn-on event is included to prevent false current

protection turnoffs due to the initial current spike resulting from circuit capacitance.

When OCD happens, outputs are placed in Hi_Z untill next PWM positive edge occurs.

During an over-temperature event, when the device junction temperature Tj is above

Tj(shutdown), the internal thermal protection circuit disables the drive outputs by driving all

outputs to the high impedance state until the device temperatures have dropped below the

lower thermal threshold temperature.

Table 36.

DC Motor Drivers - DC Specifications

(0°C

≤ T

Name

Description

Conditions

Min

Typ

Max

Units

DC Motor Over Current Threshold

(1)

1.5

A

1.

The current limitation is applied to the bottom H bridge LDMOS only, therefore over current protection applies to motor

current, but no short circuit protection exists against shorts from the DC motor outputs to ground or to VS.

Table 37.

DC Motor Drivers - AC/Transient Specifications

(0°C

≤ T

Name

Description

Conditions

Min

Typ

Max

Units

PWM frequency

10

30

KHz

Blanking time (for OCD)

1

μs

Table 38.

DC Motor Drivers Truth Table

Therm.

prot.

OCD

W2 bit 15

(SLOW

/FAST)

W0 bit 8

or 14

(PHASE)

Pin 20

or 17

(PWM)

OUT A

high side

OUT Al

ow side

OUT B

high side

OUT B

low side

Out State

0

0

0

0

0

Off

On

Off

On

L-L

0

0

0

0

1

Off

On

On

Off

L-H