AD5520 datasheet(14/24 Pages) AD

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AD5520

Rev. B | Page 14 of 24

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. They also determine which

measure mode the PMU is in, the compensation capacitor used,

and the selected current range.

STANDBY MODE

The AD5520 can be placed into standby mode via the standby

logic input. In this mode, the force amplifier is disconnected

from the force input (FIN). In addition, the switch in series with

the force output pins (FOHx) is opened, and the current

measure amplifier is disconnected from the sense resistors. The

voltage measure amplifier is still connected across the DUT;

therefore, DUT voltage measurements may still be made while

in standby mode. Figure 21 shows the configuration of the

PMU while in standby mode.

Table 5. Standby Mode

Standby

Function

Low

Normal Force Mode

High

Standby Mode

DAC

MEASIHx

MEASIL

MEASVH

MEASVL

FOHx

DUT

FIN

MEASIOUT

MEASVOUT

G = 16

G = 1

Figure 21. PMU in Standby Mode

FORCE VOLTAGE OR FORCE CURRENT

FSEL is an input that determines whether the PPMU forces a

voltage or current.

Table 6. FSEL Function

FSEL

Function

Low

Voltage Force and Current Clamp with MEASIOUT Voltage

High

Current Force and Voltage Clamp with MEASVOUT Voltage

MEASURED PARAMETER

MEASOUT is a muxed output that tracks the sensed parameter.

MSEL (digital input) connects the MEASOUT to the output of

the current sense amplifier or the voltage sense amplifier,

depending on which is the measured parameter of interest.

The MEASOUT pin is connected back to an ADC to allow the

measured value to be converted to a digital code.

Table 7. MEASOUT Connected to Voltage or Current

MSEL

Function

Low

MEASOUT = DUT Voltage

High

MEASOUT = DUT Current

The MEASOUT pin can also be made high impedance through

the MOEB logic input.

Table 8. MOEB Allows MEASOUT to Go High Impedance

MOEB

Function

Low

Enable MEASOUT Output

High

Hi-Z MEASOUT Output

CURRENT RANGES

A number of current ranges are possible with the AD5520. The

AM0, AM1, and AM2 pins are digital inputs used to establish

full-scale current range of the PMU.

Table 9. Selection of Current Range

AM0

AM1

AM2

Function

Low

Current Range MODE0 (4 μA)

High

Low

Current Range MODE1 (40 μA)

Low

High

Low

Current Range MODE2 (400 μA)

High

Low

Current Range MODE3 (4 mA)

Low

High

Current Range MODE4

(External Buffer Mode)

High

Low

High

Current Range MODE5

(External Buffer Mode)

Low

High

Standby (Same as STANDBY = High)

High

Standby (Same as STANDBY = High)

RS SELECTION

The AD5520 is designed to ensure the voltage drop across each

of the RS resistors is less than ±500 mV when maximum current

is flowing through them. To support other current ranges, these

sense resistor values can be changed. The force amplifier can

drive a maximum of 6 mA. It is not recommended to increase

the maximum current above the nominal range.

The two external current ranges use an external buffer to drive

higher current. The example in Figure 26 uses 40 mA and

160 mA ranges. These ranges can be changed to suit user

requirements for a high current range.

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