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A1185

Ultrasensitive Two-Wire Field-Programmable Chopper-Stabilized Unipolar Hall-Effect Switches

Allegro MicroSystems 

A1185 and

A1186

Ultrasensitive Two-Wire Field-Programmable

Chopper-Stabilized Unipolar Hall Effect Switches

Programming Protocol

The operate switchpoint, BOP, can be field-programmed. To do

so, a coded series of voltage pulses through the VCC pin is used

to set bitfields in onboard registers. The effect on the device

output can be monitored, and the registers can be cleared and

set repeatedly until the required BOP is achieved. To make the

setting permanent, bitfield-level solid state fuses are blown, and

finally, a device-level fuse is blown, blocking any further cod-

ing. It is not necessary to program the release switchpoint, BRP ,

because the difference between BOP and BRP , referred to as the

hysteresis, BHYS , is fixed.

The range of values between BOP(min) and BOP(max) is scaled to

31 increments. The actual change in magnetic flux (G) repre-

sented by each increment is indicated by BRES (see the Operating

Characteristics table; however, testing is the only method for

verifying the resulting BOP). For programming, the 31 incre-

ments are individually identified using 5 data bits, which are

physically represented by 5 bitfields in the onboard registers.

By setting these bitfields, the corresponding calibration value is

programmed into the device.

Three voltage levels are used in programming the device: a low

voltage, VPL , a minimum required to sustain register settings; a

mid-level voltage, VPM , used to increment the address counter

in the device; and a high voltage, VPH , used to separate sets of

VPM pulses (when short in duration) and to blow fuses (when

long in duration). A fourth voltage level, essentially 0 V, is used

to clear the registers between pulse sequences. The pulse values

are shown in the Programming Protocol Characteristics table and

in figure 4.

V+

VPH

VPM

VPL

0

Td(1)

Td(P)

Td(0)

t

Figure 4. Pulse amplitudes and durations

Additional information on device programming and program-

ming products is available on www. allegromicro.com. Program-

ming hardware is available for purchase, and programming

software is available free of charge.

Code Programming. Each bitfield must be individually set. To

do so, a pulse sequence must be transmitted for each bitfield that

is being set to 1. If more than one bitfield is being set to 1, all

pulse sequences must be sent, one after the other, without allow-

ing VCC to fall to zero (which clears the registers).

The same pulse sequence is used to provisionally set bitfields as

is used to permanently set bitfield-level fuses. The only differ-

ence is that when provisionally setting bitfields, no fuse-blowing

pulse is sent at the end of the pulse sequence.

PROGRAMMING PROTOCOL CHARACTERISTICS, over operating temperature range, unless otherwise noted

Characteristic

Symbol

Test Conditions

Min. Typ.

Max.

Units

Programming Voltage1

VPL Minimum voltage range during programming

VPM

VPH

4.5

5.0

5.5

V

11.5

12.5

13.5

V

25

26

27

V

Programming Current2

IPP tr = 11 μs; 5 V → 26 V; CBYP = 0.1 μF

-

190

-

mA

Pulse Width

td(0) OFF time between programming bits

td(1)

Pulse duration for enable and addressing

sequences

20

-

20

-

-

μs

-

μs

td(P) Pulse duration for fuse blowing

100

300

-

μs

Pulse Rise Time

tr

VPL to VPM; VPL to VPH

5

-

20

μs

Pulse Fall Time

tf

VPM to VPL; VPH to VPL

5

-

100

μs

1Programming voltages are measured at the VCC pin.

2A bypass capacitor with a minimum capacitance of 0.1 μF must be connected from VCC to the GND pin of the A118x device in order to

provide the current necessary to blow the fuse.

Allegro MicroSystems, Inc.

10

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

www.allegromicro.com

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