AD5522JSVDZ datasheet(33/65 Pages) AD

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AD5522

Data Sheet

Rev. E | Page 32 of 64

MEASURE CURRENT GAINS

The measure current amplifier has two gain settings, 5 and 10.

The two gain settings allow users to achieve the quoted/specified

current ranges with large or small voltage swing. Use the 10 gain

setting with a 5 V reference, and use the 5 gain setting with a

2.5 V reference. Both combinations ensure the specified current

ranges. Using other VREF/gain setting combinations should

achieve smaller current ranges only. Achieving greater current

ranges than the specified ranges is outside the intended opera-

tion of the AD5522. The maximum guaranteed voltage across

RSENSE = ±1.125 V.

Following are examples of VREF/gain setting combinations. In

these examples, the offset DAC is at its default value of 0xA492.

•

VREF = 5 V results in a ±11.25 V range. Using a gain setting

of 10, there is ±1.125 V maximum across RSENSE, resulting in

current ranges of ±5.625 μA, ±22.5 μA, and so on (inclu-

ding overrange of ±12.5% to allow for error correction).

•

VREF = 2.5 V results in a ±5.625 V range. Using a gain setting

of 5 results in current ranges of ±5.625 μA, ±22.5 μA, and

so on (including overrange of ±12.5% to allow for error

correction).

VREF = 3.5 V results in a ±7.87 V range. Using a gain setting of

10, there is ±0.785 V maximum across RSENSE, resulting in

current ranges of ±3.92 μA, ±15.74 μA, and so on (including

overrange of ±12.5% to allow for error correction).

VMID VOLTAGE

The midcode voltage (VMID) is used in the measure current

amplifier block to center the current ranges about 0 A. This

is required to ensure that the quoted current ranges can be

achieved when using offset DAC settings other than the default.

VMID corresponds to 0x8000 or the DAC midcode value, that

is, the middle of the voltage range set by the offset DAC setting

(see Table 13). See the block diagram in Figure 48.

VMID = 4.5 × VREF × (32,768/216) − (3.5 × VREF ×

(OFFSET_DAC_CODE/216))

VMID = 3.5 × VREF × ((42,130 − OFFSET_DAC_CODE)/216)

VMIN = −3.5 × VREF × (OFFSET_DAC_CODE/216)

VREF

VTOP

VMID

VDAC_MID

VOFFSET

DAC HV AMP

SEL×10

MEASVHx

DUTGND

INT/EXTMEASIHx

MEASURE

CURRENT

IN-AMP

MEASURE

VOLTAGE

IN-AMP

INT/EXTMEASILx

SEL×5

10R

ATT

AGND

SEL×5

VOFFSET

DAC HV AMP

AGND

ATTB

REFGND

MEASOUTx

ATT = ATTENUATION FOR MEASOUTx ×0.2

MI = MEASURE CURRENT

MV = MEASURE VOLTAGE

SEL×5 = MI GAIN = 5

SEL×10 = MI GAIN = 10

ATTB

ATT

INAMP10

INAMP1

VMIN

VDAC_MIN

DATA

ADDRESS

DAC

50Ω

Figure 48. Measure Block and VMID Influence

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