SN74HC165: Can you help check the internal block of SN74HC165

Qianqian

Genius 5010 points

Part Number: SN74HC165

Dear TI Experts

Can you help check the internal block of SN74HC165?

I'd like to know whether these three pins are connected to VCC internally:

CLK;CLK_IN;SH/LD

over 4 years ago

0 Clemens Ladisch over 4 years ago

Guru 212690 points

These three pins are CMOS inputs. HCMOS Design Considerations (SCLA007) says:

Input-Gate Circuit

A simplified schematic of a high-speed CMOS input gate is shown in Figure 25. The diode (D1) and the transistors (Q1 and Q2) provide static discharge and input transient clamping for the device. Any inputs higher than V_CC + 0.5 V or lower than –0.5 V clamp the input. The capacitors (C1 and C2) represent the parasitic capacitances present at the gate input. The data sheet specifies that the input capacitance (C1 + C2) does not exceed 10 pF (typical is about 5 pF). The input capacitance is split between V_CC and ground of the device and provides a feedback path between V_CC and the input. If the input is driven by a high-impedance source, any transient noise on V_CC may be coupled back into the input.

Figure 25. SN54/74HC Input Gate

As long as the input voltage does not exceed V_CC, the input is effectively isolated from V_CC.

0 Qianqian over 4 years ago in reply to Clemens Ladisch

Genius 5010 points

Dear TI Experts

Thank you very much

Can you help provide the internal circuit of SN74HC165 ?

We met with a problem : MCU is connected with SN74HC165 , electric to clk, which results in the voltage of the Vdd of SN74HC165

0 Clemens Ladisch over 4 years ago in reply to Qianqian

Guru 212690 points

Please show the schematic of your circuit.

0 Qianqian over 4 years ago in reply to Clemens Ladisch

Genius 5010 points

Can you help provide CLK pin's internal circuit?

I can only provide the sch to you tomorrow morning~

0 Dylan Hubbard over 3 years ago in reply to Qianqian

TI__Mastermind 41050 points

Hi Qianqian,

The datasheet shows a simplified block diagram of the CLK and Clemens provided a more detailed schematic of this input. Getting more info on the issue you are seeing and a schematic will allow me to help you debug this issue.

0 Qianqian over 3 years ago in reply to Dylan Hubbard

Genius 5010 points

Hi Dylan

Here is the schematic::

0 Dylan Hubbard over 3 years ago in reply to Qianqian

TI__Mastermind 41050 points

Hi Qianqian,

I'm still not sure what the problem is here, can you elaborate?

0 Qianqian over 3 years ago in reply to Dylan Hubbard

Genius 5010 points

Do you have the internal circuit of clk pin?

You mentioned above is not I am looking for~

0 Dylan Hubbard over 3 years ago in reply to Qianqian

TI__Mastermind 41050 points

Hi Qianqian,

That's all I can share.

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SN74HC165: Can you help check the internal block of SN74HC165