High Precision, Output Pin Programmable
Linear Hall Effect Sensor ICs
A1373 and
A1374
18
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
INITIAL STATE
After system power-up, the programming logic is reset to a
known state. This is referred to as the Initial state. All the regis-
ters that have intact fuses are set to logic 0.
While in the Initial state, any V
PL
pulses on the VOUT pin are
ignored.
To enter the Mode Selection state, send one V
PH
pulse on the
VOUT pin.
MODE SELECTION STATE
This state allows the selection of the programming mode:
" Try Value Mode. In this mode, the user provisionally downloads
settings to the device registers, without blowing the bits. The user
can increment through the codes of each parameter, and evaluate the
results of various code settings.
" Blow Fuse Mode. In this mode, after downloading the settings, the
user can blow the fuses in specific registers.
" Lock Device Mode. This mode is similar to Blow Fuse mode, except
that the fuse that is blown permanently prevents any further program-
ming of any bits in the device.
To select a mode, increment through the register bitfields by
sending V
PL
pulses on the VOUT pin, as follows:
0 pulses No effect
1 pulse Try Value mode
2 pulses Blow Fuse mode
3 pulses Lock Device mode
This register wraps by default. This means that sending addi-
tional VPL pulses traverses the register again.
Any V
PH
pulse sent before a V
PL
pulse has no effect.
To enter the Register Selection state, after sending a valid quan-
tity of V
PL
pulses, send one V
PH
pulse on the VOUT pin.
REGISTER SELECTION STATE
This state allows the selection of the register containing the
bitfields to be programmed. Selecting the register corresponds to
selecting the parameter to be set. For bit codes, see the section
Programming Logic.
" QVO [V
OUT(Q)
] Coarse. Register for setting the range of the operat-
ing dc point (2 bits)
" QVO Fine. Register for setting the value within the range set in the
QVO Coarse register (9 bits)
" Sens. [Sensivity] Coarse. Register for setting the overall gain of the
device (2 bits)
" Sens. Fine. Register for setting the value within the range set in the
Sens. Coarse register (8 bits)
" [Sensitivity] TC Register. Register for setting the temperature coef-
ficient for the device (5 bits).
" Clamp [V
OUTCLP
] Bit. Register for setting the clamping voltage of
the output (2 bits)
" Polarity Bit. Register setting the polarity of the output (1 bit)
To select a register, increment through the register bitfields by
sending V
PL
pulses on the VOUT pin. Note that the program-
ming of registers should follow the order shown in item 7 in the
section Programming Guidelines, not the bitfield selection order
shown here. The bitfield selection order is:
0 pulses QVO Coarse register
1 pulse QVO Fine register
2 pulses Sens. Coarse register
3 pulses Sense Fine register
4 pulses TC Register register
5 pulses Clamp Bit register
6 pulses Polarity Bit register
This register wraps by default.
To enter the Bitfield Selection state, send one V
PH
pulse on the
VOUT pin.
BITFIELD SELECTION STATE (Write Mode)
This state allows the selection of the individual bitfields to be
programmed, in the register selected in the Register Selection
state.
In Try Value mode, the total value of the bitfields selected incre-
ments by 1 with each V
PL
pulse on the VOUT pin. The param-
eter being programmed changes with each additional pulse, so
measurements can be taken after each pulse to determine if the
desired result has been acquired.
In Blow Fuses mode, each bitfield to be blown must be selected
individually.
For bit codes and wrapping for these registers, see the section
Programming Logic.
To leave this state, send one V
PH
pulse on the VOUT pin. If the
current mode is Try Value, the bitfields remain set and the device
reverts to the Mode Selection state. If the current mode is Blow
Fuse, the selected bitfield fuse is blown, and the device reverts to
the Mode Selection state.
Programming Protocol and State Machine Description