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AD5520
(Rev.:RevA)

Per Pin Parametric Measurement Unit/Source Measure Unit

Analog Devices 

AD5520

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.

Table I. Standby Mode

STANDBY

Low

High

Function

Normal Force Mode

Standby Mode

DAC

FIN

FOHx

MEASIOUT

MEASVOUT

G = 16

G=1

MEASIHx

MEASIL

MEASVH

MEASVL

RS

DUT

Figure 3. PMU in Standby Mode

Force Voltage or Force Current

FSEL is an input that determines whether the PPMU forces a

voltage or current.

FSEL

Low

High

Table II. FSEL Function

Function

Voltage Force and Current Clamp with

MEASIOUT Voltage

Current Force and Voltage Clamp with

MEASVOUT Voltage

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.

Table III. MEASOUT Connected to

Voltage or Current

MSEL

Low

High

Function

MEASOUT = DUT Voltage

MEASOUT = DUT Current

The MEASOUT pin may also be made high impedance through

the MOEB logic input.

Table IV. MOEB Allows MEASOUT

to Go High Impedance

MOEB Function

Low

High

Enable MEASOUT Output

Hi-Z MEASOUT Output

REV. A

–11–

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