AD5520 Analog Devices, AD5520 Datasheet - Page 11

• Manufacturer Part Number: AD5520
• Description: Per Pin Parametric Measurement Unit/Source Measure Unit
• Manufacturer: Analog Devices

THEORY OF OPERATION
The AD5520 is a single channel per pin parametric measurement
unit (PPMU) for use in semiconductor automatic test equip-
ment. It contains programmable modes to force a pin voltage and
measure the corresponding current (FVMI), force current mea-
sure voltage (FIMV), force current measure current (FIMI), and
force voltage measure voltage (FVMV). The PPMU can force or
measure a voltage from –11 V to +11 V. It can force or measure a
current over four ranges: 4 µA, 40 µA, 400 µA, and 4 mA. The
addition of an external driver allows two extended ranges.
The device provides a force sense capability to ensure accuracy
at the tester pin. A guard output is also available to drive the
shield of a force/sense pair.
The AD5520 has an on-board window comparator that pro-
vides two bits of useful information, DUT too low or too high.
Also provided on the chip is clamp circuitry that will flag via
CLHDETECT and CLLDETECT if the voltage applied to
FIN or across the DUT has exceeded the voltage applied to
CLL and CLH.
On chip is clamp circuitry that clamps the output of the force
amplifier if the voltage at MEASIOUT and MEASVOUT
exceeds CLL and CLH.
INTERFACE
The AD5520 PPMU is controlled via a number of digital inputs,
which are discussed in detail in the following sections. All inputs
are TTL compatible. CS is used to select the device while STB
(active low input) latches data available on the other digital inputs
and updates any required digital outputs. The rising edge of STB
triggers sequence inputs. The remaining digital inputs control the
function of the PMU—which measure mode it is in, which com-
pensation capacitor is used, and the selected current range.
Standby Mode
The AD5520 may be placed into standby mode via the standby
logic input. In this mode, the force amplifier is disconnected from
the force input (FIN), the switch in series with the force output
pins, FOHx, is opened, and the current measure amplifier is dis-
connected from the sense resistors. The voltage measure amplifier
is still connected across the DUT, so DUT voltage measure-
ments may still be made while in standby mode. Figure 3 shows
the configuration of the PMU while in standby mode.
REV. A
STANDBY
Low
High
Table I. Standby Mode
Normal Force Mode
Standby Mode
Function
–11–
Force Voltage or Force Current
FSEL is an input that determines whether the PPMU forces a
voltage or current.
Measured Parameter
MEASOUT is a muxed output that tracks the sensed parameter,
MSEL connects it to the output of either the current sense
amplifier or the voltage sense amplifier, depending on which is
the measured parameter of interest.
The MEASOUT pin will be connected back to an ADC to
allow the measured value to be converted to a digital code.
The MEASOUT pin may also be made high impedance through
the MOEB logic input.
MEASVOUT
MEASIOUT
DAC
FSEL
Low
High
MSEL
Low
High
MOEB
Low
High
FIN
Table III. MEASOUT Connected to
Voltage or Current
Table IV. MOEB Allows MEASOUT
to Go High Impedance
Figure 3. PMU in Standby Mode
Function
Voltage Force and Current Clamp with
MEASIOUT Voltage
Current Force and Voltage Clamp with
MEASVOUT Voltage
Table II. FSEL Function
Function
MEASOUT = DUT Voltage
MEASOUT = DUT Current
Function
Enable MEASOUT Output
Hi-Z MEASOUT Output
G = 16
G = 1
MEASIHx
MEASVH
MEASIL
MEASVL
FOHx
AD5520
R
DUT
S