TLE2064: What is max current for all channels simultaneously?

Justin Scott

Part Number: TLE2064
Other Parts Discussed in Thread: TINA-TI, , DAC8734

I am using a TLE2064IDR powered by +/-15V. Each channel is driving its own 180 nF load in unity gain. All four inputs are connected together to a -10 to 10V step. I measured the rise-time of each output to be ~50 uS in this configuration. Therefore the maximum current on each output is about 72 mA (i = C*dV/dT = 180n * 20 / 50u).

The datasheet specifies 80mA for the max output current, but it also says the max current into VCC+ and out of VCC- is 80mA. If the max current from the rail is 80 mA, how can I be getting an output current of 72 mA on 4 channels simultaneously?

Is there a way to simulate all 4 channels in Tina-TI to see how the part reacts when all 4 are loaded? I can only figure out how to do a single opamp at a time.

over 8 years ago

0 Paul Goedeke over 8 years ago

TI__Mastermind 30600 points

Hi Justin,

A schematic and simulation file would be helpful here if you could provide one. You describe that channel is driving its own 180nF load in unity gain but also seem to imply that all 4 channels are driving the same load. Are all the output pins tied together? If all the outputs are independent, there should be no issue simulating in TINA with the single channel model.

For the TLE2064, I don't see anywhere in the datasheet where it says that 80mA is the max output current - could you point me to the relevant figure or table? I see that in Figure 21 of the datasheet that for room temp, the max short circuit current is only around 50mA. The max short circuit current is also a non-linear condition and only applies when the amp output is shorted.

-Paul

0 Justin Scott over 8 years ago in reply to Paul Goedeke

Intellectual 545 points

Paul Goedeke said:
Hi Justin,
A schematic and simulation file would be helpful here if you could provide one. You describe that channel is driving its own 180nF load in unity gain but also seem to imply that all 4 channels are driving the same load. Are all the output pins tied together?

Thanks for the reply. I'm sorry I wasn't more clear. The outputs are not connected together. Each channel has its own, individual, 180nF load.

If all the outputs are independent, there should be no issue simulating in TINA with the single channel model.

I can simulate one channel at a time, but what I'm trying to figure out is the max current for the part as a whole, when all 4 channels drive their loads simultaneously.

For the TLE2064, I don't see anywhere in the datasheet where it says that 80mA is the max output current - could you point me to the relevant figure or table?

Page 5, absolute maximum ratings:

I understand that this is not a guarantee that I'm going to get 80mA out of every channel under all conditions. But even if the max short circuit current is 50mA per channel for 4 channels simultaneously, how can the max current into VCC+ be only 80mA?

0 Paul Goedeke over 8 years ago in reply to Justin Scott

TI__Mastermind 30600 points

Hi Justin,

Thanks for the clarification, I appreciate it and understand your questions. The output current spec is per channel, not for the whole amplifier. The issue of total current into VCC+ is a separate issue that we do seem to still be violating. Can you provide the screenshots/measurements for output current, input voltage, voltage across the capacitor, and supply current into VCC?

As far as modeling, I'm not aware of any way to account for the scenario of running everything together. In general, that becomes a thermal concern which is fairly easily calculated by hand. Newer devices rarely spec a total VCC current, so it's not something we normally think about as having a limit. In general, models are for typical specs and not abs max conditions.

Best,
Paul

0 Justin Scott over 8 years ago in reply to Paul Goedeke

Intellectual 545 points

Can you provide the screenshots/measurements for output current, input voltage, voltage across the capacitor, and supply current into VCC?

I have not measured current yet; I am waiting to get some test equipment in. In the screenshots below, the pink curve is the input to the TLE2064 and the green curve is the output (into the capacitive load). These curves are typical for all 4 channels.

In general, models are for typical specs and not abs max conditions.

I understand. I'm just trying to get a handle on how much current I should expect this device to draw in my application, and if I'm going to damage it by running it at such high capacitive loads. The datasheet is not clear to me.

0 Paul Goedeke over 8 years ago in reply to Justin Scott

TI__Mastermind 30600 points

Thanks Justin. I just wanted to see the voltage across the cap in case there were any other clues. It looks like your classic cap charge with a constant current curve though, so nothing really to see there.

The spec in the abs max table is likely meant as a DC spec, mostly concerned with how much constant current you expect to push through for longer periods of time. For the situations you've brought up, you may not see any ill effects because the time is so short. When the spec is violated like this over a short period of time, it is difficult to see the degradation immediately and it is difficult to know what form that degradation will take.

We can't tell you that it is okay to violate the datasheet conditions and it is going to be up to you whether or not to use the device in this manner. If this is going to be a consistent condition (ie lots of cap charge/discharge cycles) then I would recommend choosing a newer device without this limitation. I can help you with that if you provide a little information on what parameters are important to your application.

-Paul

0 Justin Scott over 8 years ago in reply to Paul Goedeke

Intellectual 545 points

Thanks, Paul. Here is what I'm looking for:

-Highest possible output current in a quad package (in order to charge output cap as fast as possible). Nothing ridiculously big though; something like an SOIC14 is fine.

-Unity gain stable

-Stable into a capacitive load of ~200 nF at unity gain. A series 50 ohm resistor precedes the capacitive load, but I would like to decrease this to get more bandwidth. Input will be a -10 to 10V step with 5 uS rise time. This is the kicker; I have tried dozens of quad opamps and the TLE2064 was the best in this regard.

-This part is being used to buffer a TI DAC8734. I need the buffer not to increase the noise of the DAC8734.

0 Mamadou Diallo over 8 years ago in reply to Justin Scott

TI__Genius 13445 points

Hi Justin,

My name is Mamadou Diallo, I am an apps engineer working with Paul and I will help recommend you some of our newer parts for your application.

Here are couple of options for you to consider:

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Please let us know if you have further questions.

Regards,

-Mamadou

0 Justin Scott over 8 years ago in reply to Mamadou Diallo

Intellectual 545 points

Thank you, Mamadou! The link doesn't seem to work. Could you please repost?

0 Mamadou Diallo over 8 years ago in reply to Justin Scott

TI__Genius 13445 points

	OPA4172	OPA4132	OPA1654	LM837	LF347

	Order now	Order now	Order now	Order now	Order now
	Online datasheet	Online datasheet	Online datasheet	Online datasheet	Online datasheet
	Datasheet	Datasheet	Datasheet	Datasheet	Datasheet
	Tools & Software	Tools & Software	Tools & Software	Tools & Software	Tools & Software

Number of Channels (# )	4	4	4	4	4
Total Supply Voltage (Max ) (+5V=5, +/-5V=10 )	36	36	36	36	36
Approx. Price (US$)	1.13 \| 1ku	5.17 \| 1ku	1.09 \| 1ku	0.55 \| 1ku	0.20 \| 1ku
Total Supply Voltage (Min ) (+5V=5, +/-5V=10 )	4.5	5	4.5	10	7
GBW (Typ ) (MHz )	10	8	18	10	3
Slew Rate (Typ ) (V/us )	10	20	10	10	13
Rail-to-Rail	In to V-	No	Out	No	In to V+
Rail-to-Rail	Out	No	Out	No	In to V+
Vos (Offset Voltage @ 25C) (Max ) (mV )	1	2	1.5	5	10
Iq per channel (Typ ) (mA )	1.6	4	2	2.5	2
Vn at 1kHz (Typ ) (nV/rtHz )	7	8	4.5	4.5	18
Rating	Catalog	Catalog	Catalog	Catalog	Catalog
Operating Temperature Range (C )	-40 to 125	-40 to 85	-40 to 85	-40 to 85	0 to 70
Package Group	SOIC	SOIC	SOIC	SOIC	PDIP
Package Group	TSSOP	SOIC	TSSOP	SOIC	SOIC
Output Current (Typ ) (mA )	75	40	50	40	31

Hi Justin,

Sorry about that.

Please see attached couple of devices that may satisfy your requirements.

Please let me know if you have further questions.

Regards,

-Mamadou

0 Justin Scott over 8 years ago in reply to Mamadou Diallo

Intellectual 545 points

Thanks; I will check these out.

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TLE2064: What is max current for all channels simultaneously?