AD5522JSVUZ Analog Devices Inc, AD5522JSVUZ Datasheet - Page 31

• Manufacturer Part Number: AD5522JSVUZ
• Description: Quad PPMU With DACs And LVDS/SPI
• Manufacturer: Analog Devices Inc

Specifications of AD5522JSVUZ

• Design Resources: Parametric Measurement Unit and Supporting Components for PAD Appls Using AD5522 and AD7685 (CN0104)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

When the AD5522 is placed in high-Z mode, the clamp circuit
is always configured to monitor the measure current signal
(irrespective of which high-Z mode is selected, high-Z V or
high-Z I). At this time, the clamp circuit is also comparing to
the voltage clamp levels. Because the device is in high-Z mode,
the measure current signal is at zero, but zero for the measure
current is always the VMID voltage set by the offset DAC. For
default offset DAC conditions, this causes no concern. For other
settings of the offset DAC, the zero point follows the VMID,
and as the clamp circuit is comparing the voltage clamp levels
to the measure current signal, there may be instances where
the voltage clamp levels cause the alarm to flag during high-Z
mode. To avoid this, the clamps can be disabled when going
into high-Z mode.
CURRENT RANGE SELECTION
Integrated thin film resistors minimize the need for external
components and allow easy selection of any of these current
ranges: ±5 μA (200 kΩ), ±20 μA (50 kΩ), ±200 μA (5 kΩ), and
±2 mA (500 Ω). One current range up to ±80 mA can be
accommodated per channel by connecting an external sense
resistor. For current ranges in excess of ±80 mA, it is necessary
that an external amplifier be used.
For the suggested current ranges, the maximum voltage drop
across the sense resistors is ±1 V. However, to allow for error
correction, there is some overrange available in the current
ranges (±12.5% or ±0.125 V across R
voltage range that can be loaded to the FIN DAC is ±11.5 V;
the forced current can be calculated as follows:
FI = 4.5 × VREF × ((DAC_CODE − 32,768)/2
MI_Amplifier_Gain)
MEASOUTx
×1 OR
×0.2
Figure 47. Addition of High Current Amplifier for Wider Current Range (>±80 mA)
SENSE
). The full-scale
VMID TO
CENTER
I RANGE
DAC
16
AGND
)/(R
FIN
×5 or ×10
×1
SENSE
+
–
+
–
+
–
Rev. D | Page 31 of 64
×
+
–
+
–
+
–
+
–
(±5µA, ±20µA, ±200µA, ±2mA)
INTERNAL RANGE SELECT
where:
FI is the forced current.
R
MI_Amplifier_Gain is the gain of the measure current
instrumentation amplifier. This gain can be set to 5 or 10
via the serial interface.
In the ±200 μA range with the 5 kΩ sense resistor and an I
gain of 10, the maximum current range possible is ±225 μA.
Similarly, for the other current ranges, there is an overrange of
12.5% to allow for error correction.
Also, the forced current range is the quoted full-scale range only
with an applied reference of 5 V or 2.5 V (with I
gain = 5). The I
voltage in such a way as to center the measure current output
irrespective of the voltage span used.
When using the EXTFOHx outputs for current ranges up to
±80 mA, there is no switch in series with the EXTFOHx line,
ensuring minimum capacitance present at the output of the
force amplifier. This feature is important when using a pin
electronics driver to provide high current ranges.
HIGH CURRENT RANGES
With the use of an external high current amplifier, one high
current range in excess of ±80 mA is possible. The high current
amplifier buffers the force output and provides the drive for the
required current.
To eliminate any timing concerns when switching between the
internal ranges and the external high current range, there is a
mode where the internal ±80 mA stage can be enabled at all
times. See Table 26 for more information.
SENSE
R
SENSE
EN
is the selected sense resistor.
2kΩ
4kΩ
4kΩ
SENSE
amplifier is biased by the VMID DAC
EXTMEASIHx
MEASVHx
DUTGND
EXTFOHx
CFFx
FOHx
EXTMEASILx
AMPLIFIER
CURRENT
HIGH
DUT
R
SENSE
SENSE
AD5522
amplifier
SENSE