A3992SBT- Allegro MicroSystems, Inc., A3992SBT- Datasheet - Page 6

• Manufacturer Part Number: A3992SBT-
• Description: DMOS Dual Full-Bridge Microstepping PWM Motor Driver
• Manufacturer: Allegro MicroSystems, Inc.

A3992
Word 1 Bit Assignments
Word 1 is selected by setting D0 = 1. Assignments are
summarized in the following table, and desribed in
detail in the remainder of this section.
D1 – D2 Blank Time.
ing factor for the current sense comparator:
When a source driver turns on, a current spike occurs
due to the reverse recovery currents of the clamp di-
odes and/or switching transients related to distributed
capacitance in the load. To prevent this current spike
D10
D11
D12
D13
D14
D15
D16
D17
D18
Bit
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
D2
0
0
1
1
Word 1 Bit Assignments
Word Select = 1
Blank Time LSB
Blank Time MSB
Off Time LSB
Off Time Bit1
Off Time Bit2
Off Time Bit3
Off Time MSB
Fast Decay Time LSB
Fast Decay Time Bit1
Fast Decay Time Bit2
Fast Decay Time MSB
C0 Oscillator Control
C1 Oscillator Control
SR Control Bit 1
SR Control Bit 2
Reserved for testing
Reserved for testing
Idle Mode
2 bits to set the blank time scal-
D1
0
1
0
1
Function
12 × P
4 × P
6 × P
8 × P
Time
OSC
OSC
OSC
OSC
Microstepping PWM Motor Driver
from erroneously resetting the source enable latch,
the sense comparator is blanked. The blank timer runs
after the off time counter to provide the programmable
blanking function. The blank timer is reset when
PHASE is changed.
D3 – D7 Fixed Off Time.
off-time for the internal PWM control circuitry. Fixed
off-time is defi ned by:
where n = 0 to 31.
For example, with a master oscillator frequency of
4 MHz ( P
able from 1.75 to 63.75 μs, in increments of 2 μs.
D8 – D11 Fast Decay Time.
decay portion of fi xed off-time for the internal PWM
control circuitry. The fast decay portion is defi ned by:
where n = 0 to 15.
For example, with a master oscillator frequency of
4 MHz ( P
able from 1.75 to 31.75 μs, in increments of 2 μs. For
t
decay mode.
D12 – D13 Oscillator Control.
options:
A 4 MHz internal oscillator can be used for the tim-
ing functions. If more precise control is required, an
external oscillator can be input to OSC pin. To accom-
modate a wider range of system clocks, an internal
divider is provided to generate the desired MO fre-
quency.
fd
> t
off
D13
t
0
0
1
1
, the device will effectively operate in fast
fd
= (1 + n) × P
t
OSC
OSC
OFF
DMOS Dual Full-Bridge
= 250 ns), the fi xed off-time is adjust-
= 250 ns), the fi xed off-time is adjust-
= (1 + n) × P
D12
0
1
0
1
OSC
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
5 bits to set the fi xed
× 8 – P
OSC
Internal clock 4 MHz
4 bits to set the fast
External clock f ÷ 1
External clock f ÷ 2
External clock f ÷ 4
Source and Rate
× 8 – P
2 bits to set timing
OSC ,
OSC ,
6