34923

MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA

10

FUNCTIONAL DESCRIPTION

Serial Interface

The 34923 is controlled via a 3-wire (clock, data, strobe)

serial port. The programmable functions allow maximum

flexibility in configuring the PWM to the motor drive

requirements. The serial data is clocked in starting with bit D19.

D0–D1, Blank Time

The current-sense comparator is blanked when any output

the oscillator input frequency.

D2–D6, Fixed Off-Time

A five-bit word sets the fixed off-time for internal PWM

current control. The off time is defined as follows:

where N = 0 to 31.

For example, with an oscillator frequency of 4.0 MHz, the off-

time is adjusted from 1.75

µs to 63.75 µs in increments of

2.0

µs.

D7–D10, Fast Decay Time

A four-bit word sets the fast decay portion of the fixed off-time

for the internal PWM control circuitry. This will only have impact

if the mixed current decay mode is selected (via bit D17 and the

operate in the fast decay mode. The fast decay portion is

defined as follows:

where N = 0 to 15.

For example, with an oscillator frequency of 4.0 MHz, the fast

decay time is adjusted from 1.75

µs to 31.75 µs in increments

of 2.0

µs.

D11–D12, Synchronous Rectification Control

The active mode prevents reversal of load current by turning

off synchronous rectification when a zero current level is

detected. The passive mode will allow reversal of current but

will turn off the synchronous rectifier circuit if the load current

D13, External PWM Decay Mode

Bit D13 determines the current decay mode when using

PWM/ENABLE chopping for external PWM current control.

Bit

Function

D0

Blank Time LSB

D1

Blank Time MSB

D2

Fixed Off-Time LSB

D3

Fixed Off-Time Bit 1

D4

Fixed Off-Time Bit 2

D5

Fixed Off-Time Bit 3

D6

Fixed Off-Time MSB

D7

Fast Decay Time LSB

D8

Fast Decay Time Bit 1

D9

Fast Decay Time Bit 2

D10

Fast Decay Time MSB

D11

Synchronous Rectification Mode

D12

Synchronous Rectification Enable

D13

External PWM Decay Mode

D14

Enable Logic

D15

Direction Logic

D16

Divisor SPAN Select

D17

Internal PWM Mode

D18

Test Mode

D19

Sleep Mode

D0

D1

Blank Time

0

0

1

0

0

1

1

1

D11

D12

Synchronous

Rect. Control

0

0

Disabled

0

1

Active

1

0

Disabled

1

1

Passive

D13

Current

Decay Mode

0

Fast

1

Slow

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com