MX868

IXYS

Bit field A[2:0] controls the digital filter operation:

A[2:0]

Time Constant

Sample Weighting

000

No Filter

1

001

T

1/2

010

3T

1/4

011

7T

1/8

100

15T

1/16

101

31T

1/32

110

63T

1/64

111

127T

1/128

Bit field B[5:0] is the full scale adjust.

Characteristics are 0.8% step size, ±25% total range.

B[5:0] = 000000 is the lowest sensitivity (highest full scale)

B[5:0] = 111111 is the highest sensitivity

One-Time Programming:

Bit Zp, when logic 1 along with A[2:0] and B[5:0] values, programs those values into the internal non-

volatile memory.

Programming a bit to logic 1 is permanent. A bit programmed to logic 1 cannot be made to go back to

logic 0.

Always send a write command with Zp = 0 and SDI = 0 immediately after the programming command.

The actual programming pulse occurs internally at the falling edge of CS* in the command following the

command in which Zp = logic 1.

The write command can be used to preview the trim bits as long as Zp is logic 0.

Examples:

The bit field B[5:0] can be programmed while the A[2:0] bit field is "000", or vice versa. For example the

total SDI bit pattern could be 10 000 001100 0000 1. This would permanently set the B[5:0] bit field to

001100 but the filter setting could still be subsequently changed by a different write command, either in

preview or programming.

The SDI bit pattern 10 010 010000 0000 0 would set the filter time constant to 3T and the full scale field

to 010000 as a preview, without making it permanent (because bit Zp = 0).

If the sample interval T = 1 mS and A[2:0] = 001 then the effective bandwidth would be 1/(2*3.14*1e-3) =

159 Hz. For this condition, if the steady state output was 2000 counts and a step input was applied that

would drive the output to 3000 counts then the digital output response would be 2000, 2500, 2750, 2875,

2937, 2968, 2984, 2992, 2996, 2998, 2999, 2999, 3000.

MX868

5

03/03/08

Drawing No. 086809

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