ATS128 datasheet(14/25 Pages) ALLEGRO

14 / 25 page

Highly Programmable, Back-Biased,

Hall-Effect Switch with TPOS Functionality

ATS128LSE

Allegro MicroSystems, LLC

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

The four BOP selecting virtual registers allow the programmer

to adjust the BOP parameter for use with a wide magnetic field

range. In addition, values can be traversed from low to high, or

from high to low. Figure 12 shows the relationship between the

BOP parameter and the different Try mode registers. Note: See the

Output Polarity section for information about setting the POL bit

before using Try mode.

The FALL and POL fields are in the same register (FALL is

bits 1:0, and POL is bit 2). Therefore, in Try mode both can be

programmed simultaneously by adding the codes for the two

parameters, and send the sum as the code. For example, sending

code 7 (111) sets FALL to 3 (x11) and sets POL (1xx).

Blow Mode

After the required code is determined for a given parameter, its

value can be set permanently by blowing individual fuses in the

appropriate register bit field. Blowing is accomplished by select-

ing the register and mode selection key, followed by the appro-

priate bit field address, and ending the sequence with a Blow

pulse. The Blow mode selection key is a sequence of eleven VPM

pulses followed by one VPH pulse. The Blow pulse consists of a

VPH pulse of sufficient duration, tBLOW, to permanently set an

addressed bit by blowing a fuse internal to the device. The device

power must be cycled after each individual fuse is blown.

A 0.1 μF blowing capacitor, CBLOW, must be mounted between

the VCC pin and the GND pin during programming, to ensure

enough current is available to blow fuses. If programming in the

application, CBYPASS (see figure 4) can serve the same purpose.

Due to power requirements, the fuse for each bit in the bit field

must be blown individually. The ATS128 built-in circuitry allows

only one fuse at a time to be blown. During Blow mode, the bit

field can be considered a one-hot shift register. Table 2 illustrates

how to relate the number of VPM pulses to the binary and decimal

value for Blow mode bit field addressing. It should be noted that

the simple relationship between the number of VPM pulses and

the required code is:

2n = Code,

where n is the number of VPM pulses, and the bit field has an ini-

tial state of decimal code 1 (binary 00000001). To correctly blow

the required fuses, the code representing the required parameter

value must be translated to a binary number. For example, as

shown in figure 9, decimal code 5 is equivalent to the binary

number 101. Therefore bit 2 must be addressed and blown, the

device power supply cycled, and then bit 0 must be addressed

and blown. The order of blowing bits, however, is not impor-

tant. Blowing bit 0 first, and then bit 2 is acceptable. A complete

example is shown in figure 13.

Note: After blowing, the programming is not reversible, even

after cycling the supply power. Although a register bit field fuse

cannot be reset after it is blown, additional bits within the same

example, if bit 1 (binary 10) has been blown, it is still possible to

blow bit 0. The end result would be binary 11 (decimal code 3).

Locking the Device

After the required code for each parameter is programmed, the

device can be locked to prevent further programming of any

parameters. To do so, perform the following steps:

1. Ensure that the CBLOW capacitor is mounted.

2. Select the Output/Lock Bit register key.

3. Select Blow mode selection key.

4. Address bit 4 (10000) by sending four VPM pulses.

5. Send one Blow pulse, at IPP and SRBLOW, and sustain it for

tBLOW.

6. Delay for a tLOW interval, then power-down.

7. Optionally check all fuses.

Figure 9. Example of code 5 broken into its binary components.

Table 2. Blow Mode Bit Field Addressing

Quantity of

VPM Pulses

Binary

Decimal Equivalent

Code

00000001

00000010

00000100

00001000

00010000

00100000

01000000

10000000

128

(Decimal Equivalent)

Code 5

Bit Field Selection

Address Code Format

Code in Binary

Fuse Blowing

Target Bits

Fuse Blowing

Address Code Format

(Binary)

1 0 1

Bit 2

Bit 0

Code 4

Code 1

(Decimal Equivalents)

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