Field-Programmable, Chopper-Stabilized,

Unipolar Hall-Effect Switches

A3251

9

Allegro MicroSystems, Inc.

115 Northeast Cutoff, Box 15036

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

www.allegromicro.com

V+

t

0

Figure 1. Pulse amplitudes and durations

PROGRAMMING PROTOCOL CHARACTERISTICS

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

Minimum voltage range during programming

4.5

5.0

5.5

V

10

11

12

V

23

25

26

V

Maximum supply current during programming

–

500

–

mA

Pulse Width

OFF time between programming bits

20

–

–

μs

Pulse duration (ON time) for enable, address, fuse

blowing or lock bits

20

–

–

μs

Pulse duration (ON time) for fuse blowing

100

300

–

μs

Pulse Rise Time

11

–

–

μs

Pulse Fall Time

5––

μs

1

Programming voltages are measured at the VCC pin.

2

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

the current necessary to blow the fuse.

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.

Programming Protocol

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

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

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

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

Characteristics table; however, testing is the only method for

ments are individually identified using 6 data bits, which are

physically represented by 6 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

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 1.

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-

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.