3958
DMOS FULL-BRIDGE
PWM MOTOR DRIVER
FUNCTIONAL DESCRIPTION (continued)
D15 Phase Logic. Bit D15, in conjunction with
PHASE, determines if the device is operating in the
forward (PHASE ≠ D15) or reverse (PHASE = D15) state.
D18 Test Mode. Bit D18 low (default) operates the
device in normal mode. D18 is only used for testing
purposes. The user should never change this bit.
PHASE D15 State
OUTA OUTB
Low High
Low
Low
High
D19 Sleep Mode. Bit D19 selects a Sleep mode to
minimize power consumption when not in use. This
disables much of the internal circuitry including the
regulator and charge pump. On power up the serial port is
initialized to all 0s. Bit D19 should be programmed high
for 1 ms before attempting to enable any output driver.
0
1
0
1
0
0
1
1
Reverse
ForwardHigh
ForwardHigh
Reverse
Low
D16 Gm Range Select. Bit D16, in conjunction with
RANGE, determines if VREF is divided by 5 (RANGE ≠
D16) or by 10 (RANGE = D16).
D19
Sleep Mode
0
1
Sleep
Normal
RANGE
D16
Divider
Serial Port Write Timing Operation. Data is clocked
into the shift register on the rising edge of the CLOCK
signal. Normally STROBE will be held high, only
brought low to initiate a write cycle. Refer to diagram
below and these specifications for the minimum timing
requirements.
0
1
0
1
0
0
1
1
÷10
÷5
÷5
÷10
D17 Internal PWM Mode. Bit D17, in conjunction with
MODE, selects slow (MODE ≠ D17) or mixed (MODE =
D17) current decay.
A. DATA setup time ......................................... 15 ns
B. DATA hold time........................................... 10 ns
C. Setup STROBE to CLOCK rising edge ....... 50 ns
D. CLOCK high pulse width ............................ 50 ns
E. CLOCK low pulse width .............................. 50 ns
F. Setup CLOCK rising edge to STROBE ....... 50 ns
G. STROBE pulse width................................... 50 ns
MODE D17 Current-Decay Mode
0
1
0
1
0
0
1
1
Mixed
Slow
Slow
Mixed
Serial Port Write Timing
STROBE
CLOCK
E
C
D
F
G
A
B
D19
D18
D0
DATA
Dwg. WP-038
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
6
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
