DS3503(2008) データシートの表示（PDF） - Maxim Integrated

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DS3503
(Rev.:2008)

NV, I2C, Stepper Potentiometer

Maxim Integrated 

NV, I2C, Stepper Potentiometer

PERIOD/2 pulses have been applied to the SYNC

input. During this disable time, the power-up or new

WR value is applied to the RW potentiometer and

position 40h (code 64 decimal) is applied to the Y

potentiometer. Additionally, the step counter is

cleared during this disable time.

After the initialization pulses, stepping is enabled again.

The RW potentiometer starts from the power-up or new

WR value and the Y potentiometer starts from position

40h (code 64 decimal). The step counter starts from

zero in the up direction.

The stepping function is further described as follows:

An internal counter called PERIODCOUNT is set equal

to PERIOD.

The input to the RW potentiometer is WR + COUNT; the

input to the Y potentiometer is code 64 + COUNT.

When a SYNC pulse is received:

PERIODCOUNT = PERIODCOUNT - 1

If PERIODCOUNT = 0 (underflow), the following actions

occur:

If direction is UP:

COUNT = min (COUNT + 1, STEPCOUNT)

RW = min (127 - STEPCOUNT, WR + COUNT);

Y = 64 + COUNT

PERIODCOUNT is reset to PERIOD

If direction is DOWN:

COUNT = max (COUNT - 1, -STEPCOUNT)

RW = max (STEPCOUNT, WR - COUNT);

Y = 64 - COUNT

PERIODCOUNT is reset to PERIOD

If COUNT = STEPCOUNT, direction is changed from

UP to DOWN.

If COUNT = -STEPCOUNT, direction is changed from

DOWN to UP.

In this way the RW output steps up to WR+STEP-

COUNT, then steps down to WR-STEPCOUNT, and then

repeats the cycle. The outputs of the RW and Y DACs

change by one LSB = (VRH - VRL)/127 per PERIOD.

STEPCOUNT and PERIOD are programmable from I2C

and are stored in the nonvolatile SCR (Table 2).

The STEPCOUNT 5-bit value programmed into

SCR<4:0> controls the stepping range reflected in the

Table 4. DAC Stepping Range

SCR<4:0>

(BINARY)

DAC RANGE

0 0000

Stepping disabled; WR is

output

0 0001

0 0010

0 0011

0 0100

0 0101

...

1 1110

...

1 1111

WR-1 to WR+1

WR-2 to WR+2

WR-3 to WR+3

WR-4 to WR+4

WR-5 to WR+5

...

WR-30 to WR+30

...

WR-31 to WR+31

RW or Y outputs per Table 4, assuming STEPCOUNT <

IVR < 127 - STEPCOUNT:

Example 1:

WR = 41h (65 decimal): SCR<4:0> = STEPCOUNT

= 10000 (16 decimal)

RW range: 49 ↔ 81 (decimal)

Y range: 48 ↔ 80 (decimal)

Example 2:

WR = 50h (80 decimal): SCR<4:0> = STEPCOUNT

= 11000 (24 decimal)

RW range: 56 ↔ 104 (decimal)

Y range: 40 ↔ 88 (decimal)

Example 3: Clamping at Lower Rail

WR = 10h (16 decimal): SCR<4:0> = STEPCOUNT

= 11111 (31 decimal)

RW range: 0 ↔ 62 (decimal)

Y range: 33 ↔ 95 (decimal)

Example 4: Clamping at Upper Rail

WR = 70h (112 decimal): SCR<4:0> = STEPCOUNT

= 11111 (31 decimal)

RW range: 65 ↔ 127 (decimal)

Y range: 33 ↔ 95 (decimal)

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