SN74HC14: VT+ and VT- spec

Shu-Cheng LIN

Guru 11785 points

Part Number: SN74HC14

Hi Sirs,

Sorry to bother you.

Because our power is 5v but datasheet spec only had 2/4.5/6

We need confirm

1. What is 5v VT+(Max & Min)& VT-(Max & Min)

2. How to check VT+ - VT- spec? because there had cover on VT+ min and VT- max

3. Our design as below, around 12Khz. I/O is 5v/10k=5mA, so the vol, voh are 5.2mA not io-20uA, right??

IO 是直接以我5V/10K= 5mA ，所以VOL VOH要以5.2mA不能用 io-20uA設計對嗎?

over 8 years ago

0 Emrys Maier over 8 years ago

TI__Guru* 97046 points

Hi Shu-Cheng,

You can determine intermediate datasheet values through linear interpolation.

At 5V,

VT+ (min) = 1.73V

VT+ (max) = 3.5

VT- (min) = 1

VT- (max) = 2.7

To measure VT- and VT+, you drive the inputs of the device with a slow triangle wave, then monitor the input and output together on an oscilloscope. You will want to drive a slow enough triangle wave that the propagation delay won't cause problems for your reading. The worst case propagation delay for this device is 31ns at 5V.

The worst case current output on the circuit shown is ~0.5mA. You should be safe assuming VOH remains at or above 4.975V (I used linear interpolation to find the output voltage drop at 0.5mA drive [4.5 V - 4.475V = 0.025V], then applied that same drop to your Vcc of 5V -> VOH(5V, 0.5mA) = 5V - 0.025V = 4.975V)

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SN74HC14: VT+ and VT- spec