A3985 Allegro MicroSystems, Inc., A3985 Datasheet - Page 12

• Manufacturer Part Number: A3985
• Description: Digitally Programmable Dual Full-Bridge MOSFET Driver
• Manufacturer: Allegro MicroSystems, Inc.

A3985
Note that, for t
full fast-decay mode.
D12 and D13 – Master Clock Control An internal
oscillator can be used for the timing functions, and if more
precise control is required, an external clock can be input to
the OSC terminal (for configuration information, refer to the
Functional Description section). To accommodate a wider
range of external system clocks, an internal divider is pro-
vided to generate the desired master clock frequency, f
according to the following table:
Bit Assignments Table
Word
*4 MHz typical, configurable with external resistor, ROSC.
0
D13
0
0
1
1
D10
D12
D13
D14
D15
D16
D17
D18
D11
Bit
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
D12
FD
0
1
0
1
> t
Register Select = 0
Bridge 1, DAC bit 0 (LSB)
Bridge 1, DAC bit 1
Bridge 1, DAC bit 2
Bridge 1, DAC bit 3
Bridge 1, DAC bit 4
Bridge 1, DAC bit 5 (MSB)
Bridge 1, Phase
Bridge 1, Mode
Bridge 2, DAC bit 0 (LSB)
Bridge 2, DAC bit 1
Bridge 2, DAC bit 2
Bridge 2, DAC bit 3
Bridge 2, DAC bit 4
Bridge 2, DAC bit 5 (MSB)
Bridge 2, Phase
Bridge 2, Mode
Range Select bit 0
Range Select bit 1
OFF
Data Register
Master Clock Source and f
, the device effectively operates in
Internal oscillator*
External clock rate
External clock rate / 2
External clock rate / 4
Function
MCK
MCK
,
Dual Full-Bridge MOSFET Driver
Word
1
D14 and D15 – Synchronous Rectification Two bits
are used to set the mode for sunchronous rectification. The
modes are described in the synchronous rectification section
of the Functional Description section.
D16 and D17 – Reserved These bits are reserved for test-
ing and should be programmed to 0 during normal operation.
D18 – Idle Mode The device can be placed in a low power
mode by writing a 0 to D18. This disables the outputs and
the device draws a lower load supply current. The undervolt-
age monitor circuit remains active. When leaving idle mode,
D18 should be set to 1 for 1 ms before attempting to enable
any output driver.
D10
D12
D13
D14
D15
D16
D17
D18
D11
Bit
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
D15
0
0
1
1
Register Select = 1
Blank-time bit 0 (LSB)
Blank-time bit 1 (MSB)
Off-time bit 0 (LSB)
Off-time bit 1
Off-time bit 2
Off-time bit 3
Off-time bit 4 (MSB)
Fast-decay time bit 0 (LSB)
Fast-decay time bit 1
Fast-decay time bit 2
Fast-decay time bit 3 (MSB)
Master Clock Control bit 0 (LSB)
Master Clock Control bit 1 (MSB)
Synchronous Rectification Control bit 0 (LSB)
Synchronous Rectification Control bit 1 (MSB)
Reserved
Reserved
Idle Mode
Digitally Programmable
Control Register
D14
0
1
0
1
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
Rectification Mode
Function
Synchronous
Disabled
Disabled
Passive
Active
12