Using Maxim's driver-comparator-load (DCL) devices and parameter measurements

Eliminate external relays by leveraging the built-in functionality of Maxim driver-comparator-load (DCL) devices and parametric measurement unit (PMU) chipsets

Abstract: This application note describes the capabilities of Maxim's new PMU and DCL products and uses their features to meet specific PMU applications with output currents below 2mA or in the 2mA to 50mA range.

Overview

In traditional semiconductor automated testing, DCLs and PMUs alternately connect the device under test (DUT) via "selector relays."

This application note details the unique features of Maxim DCLs (MAX9961/62, MAX9967/68) and PMUs (MAX9949/MAX9950, MAX9951/MAX9952) that enable users to eliminate the cost and board space of mechanical relays. A secondary benefit is the ability to leverage the DCL's drive circuitry to improve the drive capability of traditional low-current PMUs.

Device Description

The MAX9961/62/67/68 are dual-channel, low-power, high-speed pin electronics DCL ICs for automatic test equipment (ATE). Each channel includes a 500Mbps driver, a window comparator, dynamic clamping circuitry, and active load (MAX9961/62 = 2mA, max; MAX9967/68 = 35mA, max).

The MAX9949/50 are dual-channel PMUs for ATE and other instrumentation. The small size, wide force/measure range, and high accuracy make the MAX9949-50 ideal for applications that require a PMU per pin or per test point. The MAX9949/50 have built-in buffered drivers that extend the PMU voltage and current ranges as required by the user.

Application Examples

The internal force/sense and low-leakage features of the MAX9961/MAX9962/67/68, along with the external buffer support of the MAX9949/50, enable these chips to work together, eliminating the need for external relays.

Circuit Description

PMU applications requiring Iout < 2mA
In this mode, the PMU uses its internal range selector switch for force and measurement. The device is in low leakage mode and the PMU is connected to the DUT through the force pin of DCL ( Figure 1 ).


Figure 1.

PMU applications requiring 2mA < Iout < 50mA
In this mode, the PMU uses its external range selector function for force and measurement. The reference input of the driver is connected to the Rcom output of the PMU. The PMU's current sense amplifier is used to measure the voltage across the DCL force/sense pin, which is used to measure the DUT current through the 45Ω driver output resistor ( Figure 2 ).


Figure 2.

in conclusion

Maxim's DCL and PMU with analog switches can eliminate the need for mechanical potentiometers, thereby reducing costs and saving board space. When using a low-current PMU in a design, DCL can be used to increase current drive capability.