a8291 Allegro MicroSystems, Inc., a8291 Datasheet - Page 11

• Manufacturer Part Number: a8291
• Description: A8291 Single Lnb Supply And Control Voltage Regulator
• Manufacturer: Allegro MicroSystems, Inc.

A8291
Control Registers
All main functions of the A8291 are controlled through the I
compatible interface via the 8-bit Control registers. As the A8291
contains numerous control options, it is necessary to have two
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
(I
VSEL0 These three bits provide incremental control over the voltage on the LNB output.
VSEL1 The available voltages provide the necessary levels for all the common standards
VSEL2 plus the ability to add line compensation in increments of 333 mV. The voltage
VSEL3 Switches between the low level and high level output voltages on the LNB output.
ODT
ENB
I0
I1
2
C™-Compatible Write Register)
Table 2. Control Register Address (I1, I0) = 00
Single LNB Supply and Control Voltage Regulator
levels are defined in table 4, Output Voltage Amplitude Selection.
0 selects the low level voltage and 1 selects the high level. The low-level center voltage
is 12.709 V nominal and the high level is 18.042 V nominal. These may be increased
in steps of 333 mV using the VSEL2, VSEL1 and VSEL0 control register bits.
The overcurrent disable timer is always enabled.
Enables the LNB output. When set to 1 the LNB output is switched on. When set to
0, the LNB output is disabled.
Address
Address
Bit
0
1
2
3
4
5
6
7
VSEL0
VSEL1
VSEL2
VSEL3
Name
ODT
ENB
I0
I1
See table 4, Output Voltage Amplitude Selection
0: LNB = Low range
1: LNB = High range
1 (recommended): The ODT functions are always
enabled, but setting 1 recommended at all times.
0: Disable LNB Output
1: Enable LNB Output
Address Bit: 0
Address Bit: 0
2
C™-
control registers. Each register contains up to 6 bits of data (bit
0 to bit 5), followed by 2 bits for the register address (bit 6 and
bit 7). The power-up states for the control functions are all 0s.
and the settings for output voltage:
The following tables define the control bits for each address
Function
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
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