Sensitive Two-Wire Field-Programmable

Chopper-Stabilized Unipolar Hall Effect Switches

A1180, A1181,

13

Allegro MicroSystems, Inc.

115 Northeast Cutoff, Box 15036

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

www.allegromicro.com

V+

t

0

Address 1

Address 2

Address n (

≤ 31)

Figure 8. Pulse sequence to select addresses

V+

t

0

Encode Lock Bit

Enable

Address

Blow

32 pulses

Figure 9. Pulse sequence to encode lock bit

Lock Bit Programming.

is programmed, and all of the corresponding bitfield-level fuses

are blown, the device-level fuse should be blown. To do so, the

lock bit (bitfield address 32) should be encoded as 1 and have

its fuse blown. This is done in the same manner as permanently

setting the other bitfields, as shown in figure 9.

Address Selection

.

After addressing mode is enabled, the

shown in figure 8.

Figure 7. Addressing mode enable pulse sequence

V+

t

0

Enabling Addressing Mode

.

The first segment of code is a

keying sequence used to enable the bitfield addressing mode. As

ruptions. This sequence is designed to prevent the device from

being programmed accidentally, such as by noise on the supply

line.