MC34923 데이터 시트보기 (PDF) - Freescale Semiconductor
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MC34923 Datasheet PDF : 16 Pages
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Freescale Semiconductor, Inc.
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.
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
The current-sense comparator is blanked when any output
driver is switched on in accordance with the table below. fosc is
the oscillator input frequency.
D0
D1
Blank Time
0
0
4 / f osc
1
0
6 / f osc
0
1
12 / f osc
1
1
24 / f osc
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:
toff = (8[1 + N] /fosc) - 1/fosc
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
PWMMODE input pin). For tfd > toff, the device will effectively
operate in the fast decay mode. The fast decay portion is
defined as follows:
tfd = (8[1 + N]/fosc) - 1/fosc
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
inversion ramps up to the current limit set by VREF/RS.
D11
D12
Synchronous
Rect. Control
0
0
Disabled
0
1
Active
1
0
Disabled
1
1
Passive
D13, External PWM Decay Mode
Bit D13 determines the current decay mode when using
PWM/ENABLE chopping for external PWM current control.
D13
Current
Decay Mode
0
Fast
1
Slow
34923
10
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
For More Information On This Product,
Go to: www.freescale.com
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