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Fast parametric measurement-unit chips have small footprints

Posted: 01 Aug 2005 ?? ?Print Version ?Bookmark and Share

Keywords:bicmos ic? ate? automatic test equipment? pin-count tester? pmu?

It's not often that I get to examine semiconductors for test; most test-and-measurement products are board- or box-level products. Here's a family of BiCMOS ICs, however, that will appeal to those of you developing ATE (automatic test equipment).

These devices are intended to let you develop cost-effective high pin-count testers with a PMU (parametric measurement unit) per-pin. Admittedly not every EE or test engineer is designing a multi-million dollar tester, but they're significant nonetheless.

Expanding a product line

Expanding its existing line of standards-based PPMU (per-pin parametric measurement unit) silicon, chip maker Semtech Corp.'s family of three PPMU devices are claimed to have extremely fast settling times and the smallest form-factors for 40mA devices.

The fast settling times of these devices should dramatically shorten application test times. That can translate into an increase in a tester's throughput. The result can be a decrease in the overall cost of test.

The use of BiCMOS fab also permits them to accommodate a wide 16.25V range.

In terms of packaging, the E4237 and the E4257 come in 9-by-9mm 64-pad LPCC (leadless plastic chip carriers). LPCCS were developed by Asat back in 1998.

The use of LPCCs renders these devices about 70% smaller/channel than competing 40mA ICs. For its part, the E4287 comes in a 14-by-14mm MQFP (metric quad flat pack) package.

Some specs

Let's look a bit more closely at this low output-capacitance silicon. The Type E4237, E4257 and E4287 chips all feature dual-channels for forcing or measuring voltage and current. Digital inputs determine whether you're forcing voltage or forcing current, or measuring voltage or current.

Slated for general-purpose applications are the E4257 (it supports four current ranges), and the E4287 (it offers the same four current ranges, along with an analog MUX that can help do flash programming). The E4287 also includes a driven guard pin to assist making low-current measurements.

Four-quadrant operation

All of these ICs operate over a -3.25V to 13V range. Operable in all four quadrants, the E4287 and E4257 can deliver 40?A, 4mA and 40mA. The E4237 has two current ranges, of 40?A and 40mA.

Integrated on-chip are voltage clamps and short circuit protection, so they should serve well in relay-less testers. The on-chip clamps will protect a DUT (device under test) from voltage stress and possible damage. The clamp levels are set by external analog voltages.

Each of these ICs also features an on-board window comparator. It can be used to determine if a measurement value is within a user-defined range. That's just the ticket for Go/No-Go testing.

These ICs are also stable driving up to 300pF of capacitive, with no external compensation caps needed. They are, however, digitally selectable for compensation, so you can use them with bigger capacitive loads, as great as 10nF. Pins support external compensation cap values.

Price and availability

According to Semtech, all devices in the family are available now in production quantities. Pricing for up to 1,000-units of an E4287AHF flavor is about $28 in, packaged in an 80-pin MQFP with built-in heat spreader.

An E4257ALP comes in at about $25 each, packaged in a 64-pad LPCC. The E4237ALP member is priced at about $22, and is available in a 64-pad LPCC. All of these ICs are also available in tape-and-reel put-ups.

- Alex Mendelsohn


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