Hi,
When the ALM2403 output is shorted to GND or power supply (9, 13.5, 16V), how should the chip design be considered?
For example, if it is shorted to 16V, a larger current will flow through the internal FET of the chip. How does the chip respond? Will it cause heat problem?
Thanks!
Hi Mingkong,
How does the chip respond? Will it cause heat problem?
The ALM2403-Q1 is able to withstand the Vout shorted to GND continuously at room temperature. It is only limited to one of the output terminal, not both. Yes, the power amplifier will heat up, but the heat dissipation will not exceed the Tj temperature or result in a thermal shutdown. The Tj's internal thermal shutdown is occurred at approx. 172C.
When the ALM2403 output is shorted to GND or power supply (9, 13.5, 16V), how should the chip design be considered?
ALM2403-Q1's abs. max. rating is 26Vdc for a single supply rail. As long as the 26Vdc rating is not exceeded, when one of the Vout pin is shorted to battery terminals at the above specified voltages, no additional fault protection is required. For the specific fault conditions, we can simulate these cases via Tina. Please take a look at the following application note.
If you have additional questions, please let me know.
Best,
Raymond
Hi Mingkang,
Q：Will short circuits to the battery or GND also not exceed the Tj temperature or result in a thermal shutdown at high and low temperatures（-40℃~105℃）？
ALM2403-Q1's Vout is shorted to GND:
At Tamb < 25C, the previous reply still valid, where the ALM2403-Q1 is able to withstand the Vout shorted to GND continuously at room temperature.
At Tamb > 25C, the ALM2403-Q1's Tj may exceed the typical 172C, which results the thermal shutdown. The shutdown protection feature is to protect itself without thermal destruction.
ALM2403-Q1's Vout is shorted to battery terminal (9, 13.5, 16):
Assume that ALM2403-Q1 is under nominal operating condition (output swing = 7Vrms at 10kHz typical), and only one of the output lead is shorted to battery terminal. The power amplifier's Tj will rise continuously under the fault condition depending on the voltage drop across driving mosfets. Although the power amplifier may not be damaged electrically, the IC's internal temperature Tj may exceed 172C (typ), and result a thermal shutdown. We have to perform thermal analysis individually in order to estimate the end result.
Please keep in mind that Tj of 172C is to protect itself thermally. When the IC is operating at elevated temperature, say Tj >150C, it will affect the life span of the power amplifier. ALM2403-Q1 Operating Tj < 125C is ideal, and lower the junction temperature will be better. The prolonged high temperature exposures will affect the life span of the part, which it should be prevented.
Please also note that the thermal shutdown recovery temperature is at approx. 150C. If the IC may be cooled down below the recovery temperature for some reasons, the part may resume operation below the thermal threshold. The thermal oscillation or cycles may be possible, if the fault condition is not intervened.
Q：if both of the output terminal short to GND or battery，what will happen?
If ALM2403-Q1 is operating under a nominal condition (7Vrms @10kHz or similar), the Tj will increase rapidly and result a thermal shutdown.
These failure events are tied to the customer's fault condition design requirements. If the design requirements are required to protect either or both resolver driver and/or resolver under such fault conditions, customer may implement a current sensing circuit within the driving loop. When the resolver current exceeds a certain threshold, the current comparator and/or GPIO may instruct ALM2403-Q1's OTF/SH_DN pin to shut down the resolver driver manually, and protect both drivers under the scenarios. Several fault conditions may be combined using AND logic conditions and drive OTF/SH_DN pin to protect these faults.
If you have other questions, please let me know.
Best,
Raymond
Hi QWB,
Under these working conditions, the IC will be OK in Short circuit condition?
The ALM2403-Q1's Vout shorted to GND at 105C may trigger the Over Temp Flag (OTF) and result a thermal shutdown on the fault condition for 15 minutes.
I think that inserting 200mΩ current sensing resistor that may be the best option to prevent the overheating over the wide temperature range.
The simulation below is shown that the upper ALM2403-Q1's output terminal is shorted to GND, while the input SPWM signals and ALM2403-Q1 are in operating conditions. The example is shown that the ALM2403-Q1's output swing is specified at approx. 7Vrms or 20Vpp at 10kHz, and Vs = 16Vdc.
With the upper ALM2403-Q1's output terminal shorted to GND, 16Vdc is dropped across the upper power amplifier. Up to 0.5A may be sourced to GND for 50% of sinusoidal cycles via upper PMOS driver which is approx. 4W. The PMOS's drain and source will exhibit positive temperature coefficient (PTC), and the actual sourced current depend on the internal Tj temperature (higher short circuit current at -40C and lower short circuit current at 105C). Under the shorted circuit condition, the ALM2403-Q1 may trigger the OTF flag under extreme Tamb conditions (e.g. -40C or 105C in Tamb).
By inserting 200mΩ sensing resistors inside of the ALM2403-Q1's feedback loop, the overcurrent conditions can be readily detected by MCU or logic circuitries, and activate OTF/SH_DN pin to shutdown the ALM2403-Q1 drivers. We may use instrumentation amplifier (IA), current monitor or overcurrent comparator circuitries to detect the overcurrent conditions, trigger the fault conditions at the output.
With the upper ALM2403-Q1's output terminal shorted to Vbattery or 16Vdc, similar overcurrent event will occur at the output driver. Under the scenario, NMOS will sink the current up to 0.4A range and result the ALM2403-Q1 in the over temperature conditions.
There are other alternative prevention approach to deal with fault conditions, but these fault circuitry events all have to be validated for the various "short" scenarios that defined in the design requirements. Enclosed is the Tina simulation that you may be checked out.
ALM2403-Q1 SPWM Input Short to GND 03282024.TSC
Also, some of other fault circuit prevent suggestions are covered in the following application note. The protection circuitries depend on how these fault protection requirements are defined.
https://www.ti.com/lit/an/sboa447/sboa447.pdf?ts=1711619122590
If you have other questions, please let me know. In addition, I can help you to suggest some of the protection circuitries, if I have the information the complete protection requirements.
Best,
Raymond
