Data Sheet
AD5522
Rev. E | Page 33 of 64
CHOOSING POWER SUPPLY RAILS
variation across the part |AVDD AVSS| ≥ 20 V. For the
AD5522 circuits to operate correctly, the supply rails must take
into account not only the force voltage range, but also the
internal DAC minimum voltage level, as well as headroom and
so on. The DAC amplifier gains VREF by 4.5, and the offset
DAC centers that range about some chosen point.
The supplies need to cater to the DAC output voltage range to
avoid impinging on other parts of the circuit (for example, if the
measure current block for rated current ranges has a gain of
10/5, the supplies need to provide sufficient headroom and
footroom to not clip the measure current circuit when full
current range is required).
Also, the MEASOUT gain = 0.2 setting uses the VMIN level for
scaling purposes; if there is not enough footroom for this
VMIN level, then the MV and MI output voltage range is
affected.
For the MEASOUT gain = 0.2 setting, it is important to choose
AVSS based on the following:
AVSS ≤ 3.5 × (VREF × (OFFSET_DAC_CODE/216))
AVSS_footroom VDUTGND (RCABLE × ILOAD)
where:
AVSS_footroom = 4 V.
VDUTGND is the voltage range anticipated at DUTGND.
RCABLE is the cable/path resistance.
ILOAD is the maximum load current.
MEASURE OUTPUT (MEASOUTx PINS)
The measured DUT voltage or current (voltage representation
of DUT current) is available on the MEASOUTx pin with respect
to AGND. The default MEASOUTx range is the forced voltage
range for voltage measure and current measure (nominally
±11.25 V, depending on the reference voltage and offset DAC)
and includes some overrange to allow for offset correction.
The serial interface allows the user to select another MEASOUTx
range of 0.9 × VREF to AGND, allowing an ADC with a 5 V
input range to be used. The MEASOUTx line for each PMU
channel can be made high impedance via the serial interface.
The offset DAC directly offsets the measured output voltage level,
but only when GAIN1 = 0. When the MEASOUT gain is 0.2, the
minimum code from the DAC is used to center the MEASOUTx
voltage and to ensure that the voltage is within the range of 0 to
When using low supply voltages, ensure that there is sufficient
headroom and footroom for the DAC output range (set by the
VREF and offset DAC setting).
DEVICE UNDER TEST GROUND (DUTGND)
By default, there is one DUTGND input available for all four
PMU channels. However, in some PMU applications, it is
necessary that each channel operate from its own DUTGND
level. The dual function pin, GUARDINx/DUTGNDx, can be
configured as an input to the guard amplifier (GUARDIN) or
as a DUTGND input for each channel.
The pin function can be configured through the serial interface
on power-on for the required operation. The default connection
is SW13b (GUARDIN) and SW14b (shared DUTGND).
Table 10. MEASOUTx Output Ranges for GAIN1 = 0, MEASOUT Gain = 1
MEASOUT
Function
Measure
Current Gain
Transfer Function
Output Voltage Range for VREF = 5 V1 Offset DAC = 0x0
Offset DAC = 0xA492
Offset DAC = 0xED67
MV
5 or 10
±VDUT
0 V to 22.5 V
±11.25 V
16.26 V to +6.25 V
MI
GAIN0 = 0
10
(IDUT × RSENSE × 10) + VMID
0 V to 22.5 V
±11.25 V
16.26 V to +6.25 V
GAIN0 = 1
5
(IDUT × RSENSE × 5) + VMID
0 V to 11.25 V
(VREF = 2.5 V)
±5.625 V
(VREF = 2.5 V)
8.13 V to +3.12 V
(VREF = 2.5 V)
1
VREF = 5 V unless otherwise noted.
Table 11. MEASOUTx Output Ranges for GAIN1 = 1, MEASOUT Gain = 0.2
MEASOUT
Function
Measure
Current Gain
Transfer Function
Output Voltage Range for VREF = 5 V1, 2 MV
5 or 10
0.2 × (VDUT × VREF × OFFSET_DAC_CODE/216)
0 V to 4.5 V (±2.25 V centered around 2.25 V)
MI
GAIN0 = 0
10
(IDUT × RSENSE × 10 × 0.2) + (0.45 × VREF)
0 V to 4.5 V (±2.25 V centered around 2.25 V)
GAIN0 = 1
5
(IDUT × RSENSE × 5 × 0.2) + (0.45 × VREF)
1.125 V to 3.375 V (±1.125 V, centered around 2.25 V)
0 V to 2.25 V (±1.125 V, centered around 1.125 V)
(VREF = 2.5 V)
1
VREF = 5 V unless otherwise noted.
2
The offset DAC setting has no effect on the output voltage range.