SN74HCS541-Q1: VOH @3.3Vcc

Thanks. it's useful. but we'd like to know if you can offer the VOH and VOL when IOH = +/-10mA @3.3Vcc. We're considering to add this buffer in front of the gate driver (UCC23513). So we'd like to get VOH/VOL at  this condition. thanks. 

Thanks. In the d/s of the SN74HCS541, the continuous output current says +/-35mA. is it for total 8ch current? or each ch?

That is per channel. The limit for the total current is 70 mA.

So, if the +/-35mA is for the per channel, i think the SN74HCS541 should work with conditions of the 3.3Vcc and 10mA current and 6ch. The total ch in application is only 6ch for AC inverter PWM buffer. is should work, correct? double checking with you.  

At 10 mA, there are no guarantees about V_OH/V_OL. How do you limit the current to 10 mA? There might not even be 2.4 V left.

Regarding to the plot of Fig6-1 and Fig6-2 you attached, where to obtain that plots with output resistance behavior since i don't find it in the SN74LVC541 d/s.

also, with this plot, it's at 25degree ambient? or it's apply to full temp range. Since we're estimate the output resistance in the gate driver application, we would need such info. with full temp range. could you support this? Very thanks.  

Regards

Brian W

For LVC, the resistance is essentially constant as long as you stay below 32 mA.

The two plots above show typical values, and go beyond the recommended operating conditions, so there are no guarantees. LVC devices are fully specified for 10 mA.

Thanks. you mentioned that the above two plots can be applied to full temp range of -40 to 105degree if the current is below 32mA?

and how to get those plots from TI.com?

Thanks. So the output resistance of the SN74LVC541A in LOW state is 0.55V/24mA = 2.29 Ohm, correct?

If so, the output impedance of the LVC541 is much lower than HCS541 typically, correct?

To follow up the question here.

Since customer condition is IOL=10mA and VCC=3.3V,typ +/-3% variation, how about the VOL and its conduction resistance? could you offer such data since customer need more precise parameters on gate driver calculation. Please help on this. Very thanks.  

For currents inside the recommended operating conditions, the output resistance is essentially constant. (See [FAQ] What is the output voltage (VOH or VOL) when the output current is X or the supply voltage is Y?) So you have about 12 Ω typical, 22.9 Ω max.

Thanks. 

It's a useful link. But i still would like to double check with you when VOL is determined with 3.3V and 10mA on SN74LVC541. 

Rout = (VCC - VOH)/IOH, here using the SN74LVC541 for example, Rout=(3.0Vcc - 2.4VOH) / 12mA = 50 Ohm. So the VOH at 3.3Vcc and 10mA is 3.3Vcc- 0.01A x 50 Ohm = 2.8V. 

Since we wondering to get VOL at conditions of 3.3V and 10mA, When IOL=10mA, the VOL = 10mA x 50 Ohm = 0.5V at 3.3Vcc, is that correct to take 50 Ohm into account? When new VOL is calculated, should Vcc needs to be taken into account? here i have a little confused. thanks. 

You should use the 24 mA V_OH value to compute Rout. (I do not know why a 12 mA value is specified for 3 V; probably compatibility with some other logic family.)

The Rout can be different for high-level and low-level outputs.

Rout decreases with larger supply voltage.

With your inputs, pls check if below calculation is correct or not?

Step 1: From datasheet E/C table, Rout = (3.0Vin - 2.2VOH) / 24mA = 33.33 Ohm.

Step 2: To get new VOH with conditions of the 10mA and 3.3Vin; VOH = 3.3VIN - (10mA x 33.33 Ohm) =2.967V.

Step 3:  To get new VOL with conditions of the 10mA and 3.3Vin, VOL = 10mA x 33.33 Ohm =0.3333V.

Are above calculation correct? Thanks

Brian 

Rout for low-level outputs is different (0.55 V / 24 mA).

So, the calculation should be as below, correct?

Rout_low side = 0.55V/24mA = 22.9 Ohm.

If sinking current is 10mA, the VOL is 10mA x 22.9 Ohm = 0.229, is this correct?

It seems that the VCC is nothing to do with new VOL calculation, correct?

Regards

Brian