Power IC failures: Analysis and Solutions how to avoid them

Power IC failures:
Analysis and Solutions how to avoid them

Nobody likes component failures, but they sometimes do happen. Finding the root cause can be tricky, especially if it concerns a sporadic failure that cannot be repeated. At Richtek, we have analysed many failure cases. We found that most power ICs are damaged because of Electrical Over Stress (EOS) on the IC input supply pins. But how does EOS happen and how does the IC actually fail? In this article you will find some answers and solutions how to avoid EOS in your design or end product.

Understand Buck Power IC Input Structure

The diagram on the right side shows the basic block diagram of a buck converter IC with various ESD protection cells such as BOOT pin, EN pin and FB pin. The input supply pin is protected via a large ESD cell, which basically protects the regulator and MOSFETs from high ESD voltage. There is a relationship between IC input pin absolute maximum voltage, ESD cell activation voltage and IC maximum process voltage.

Differences between ESD and EOS

Both ESD (Electro Static Discharge) and EOS (Electrical Over Stress) are related types of voltage overstress. The clear difference is that ESD is a very high voltage (>500V) with relatively short duration (<1μsec) whereas EOS is a moderate voltage (<100V) with longer time span (normally>1μsec). Richtek IC ESD cells are designed to survive the energy of an ESD pulse based on Human Body Model (HBM) or CDM (Charged Device Model), which are well quantified and represent a certain energy surge in the ESD cell. EOS events are longer duration events, and the energy surge during EOS can easily exceed the levels of ESD events.

Measuring ESD cell characteristics

To see the point where IC failure starts to happen, you can measure the actual ESD breakdown voltage, either via a curve tracer or by applying a pulsed current to the device under test, which is a more precise measurement to check the actual ESD cell failure point. The ESD cell maximum surge energy can be calculated from these measurements.


The Buck converter RT7285C VIN ESD cell breakdown lies around 25.5V, and rises sharply without snap-back.	A simple switched current source with adjustable current and pulse width can show the ESD cell breakdown and by increasing the current the failure point can be captured.

Common reasons for VIN EOS: Supply hot-plug

One of the most common reasons for power IC VIN EOS is power supply hot-plug events. Appliances that run from wall adapters with DC jacks should always consider hot-plug events. In the lab it is easy to duplicate the hot plug event by connecting live power supply leads to an application which has low ESR ceramic input capacitors. The amplitude of the voltage spike depends on several parameters like cable wire type and length, supply impedance, input capacitor ESR and the MLCC DC bias effect.

There are several ways to reduce the voltage ringing amplitude during hot-plug : You can increase the output impedance of the switch-mode adapter input supply, you can increase the adapter cable resistance or improve the coupling between positive and negative wires. Another solution is to add an RC snubber at the converter input. For more details on these solutions

DIY tools for generating EOS

Read here how to build these handy tools for stress testing your design on EOS.

Breakdown characteristics of different ESD cell types
Other causes for power IC VIN EOS and their solutions

For more details, please download the full application note
“Analysing VIN Overstress in Power ICs”

Feature Product

RT6204 - Richtek’s latest addition to the wide VIN converter range

RT6204 is a Synchronous Buck converter with a wide input range of 5.5V to 60V and an output range adjustable from 0.8V to 50V with 500mA current capability.

It switches at 350kHz and is housed in a SOP-8 thermally effective package.

The wide input range in combination with high step down capability makes it suitable for virtually any industrial application range, from battery fed automotive to 12V/24V/48V industrial supplies.

Featuring PSM mode for enhanced light load efficiency, RT6204 uses current mode topology with external compensation, allowing great flexibility in loop tuning using either ceramic or electrolytic output capacitors. The 80V max rating makes this IC very tolerant to hot-swapping and other supply voltage transients. Slew rate limited switching helps to reduce EMI radiation.

Applications: automotive electronics, solar power systems, networking and telecommunication systems, industrial and communication low power systems, LCD monitors and TVs, LED lighting, motor drive bias supply, etc.

Please contact our sales offices for samples to get your design started in no time.

New Products

	RT9072A/B is a wide 4.5V to 80V input, wide 1.25V to 60V output, 20mA Low dropout voltage Linear Regulator in SOT-23-5 package. -80V reverse-battery protection, ±3% output tolerance over line, load & temperature range and low quiescent current make it a robust solution for powering sensors or MCUs in battery-powered applications, telecom and Datacom, automotive applications, etc.
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	RT6216 / RT6217 ACOT® Synchronous Buck Converters family are 4.5V to 23V input, 2.5A/3A output current, 500kHz or 800kHz for options, in compact TSOT-23-8 packages. The ACOT topology provides ultra-fast transient response, and a constant switching frequency, ideal for Set Top Box, portable TV, access point router, DSL modern and LCD TV powered from 5V, 12V or 19V supplies. Also see other ACOT® products