Highly Programmable, Back-Biased,

Hall-Effect Switch with TPOS Functionality

ATS128LSE

17

Allegro MicroSystems, LLC

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Fuse Checking

Incorporated in the ATS128 is circuitry to simultaneously check

the integrity of the fuse bits. The fuse checking feature is enabled

by using the Fuse Checking registers, and while in Try mode,

applying the codes shown in table 3. The register is only valid

in Try mode and is available before or after the programming

LOCK bit is set.

Selecting the Fuse Threshold High register checks that all blown

fuses are properly blown. Selecting the Fuse Threshold Low

register checks all un-blown fuses are properly intact. The supply

If all fuses are correctly blown or fully intact, there will be no

change in supply current.

Output Polarity

is determined by the value of the Output Polarity bit (POL). The

default value is POL = 0 (fuse un-blown). For applications that

require the output states defined by POL = 1 (see Operating Char-

acteristics table), it is recommended to first permanently blow the

POL bit by selecting the Output / Lock bit register, and code 4.

Try mode registers. See table 3 for parameter details.

Additional Guidelines

The additional guidelines in this section should be followed to

ensure the proper behavior of these devices:

• The power supply used for programming must be capable of

down the device after blowing each bit.

• Set the LOCK bit (only after all other parameters have been

programmed and validated) to prevent any further programming

of the device.

Read Mode

The ATS128 features a Read mode that allows the status of each

programmable fuse to be read back individually. The status,

blown or not blown, of the addressed fuse is determined by moni-

toring the state of the VOUT pin. A complete example is shown

in figure 11.

Read mode uses the same register selection keys as Blow mode

(see table 3), allowing direct addressing of the individual fuses in

the BOPPOL and BOPSEL registers (do not inadvertently send a

Blow pulse while in Read mode). After sending the register and

pulse in the key, the first bit (the LSB) is selected. Each addi-

(BOPSEL) and reading back the status of each of the eight bit fields. In this example, the code

GND

Register (and Mode) Selection Key

Bit Field (Fuse) Address Codes

Read-out on VOUT pin

1234567

1

234567

8

9 10 11

GND

Fuse intact

Fuse blown

Don’t Care