8 Detailed Description

8.1 Functional Block Diagram

RCLK

OE

SRCLR

SRCLK

SER

13

12

10

11

14

D

R

15

1

Q

A

Q

C

Q

D

R

Q

D

Q

D

Q

2

Q

D

3

Q

E

4

5

Q

G

6

D

R

7

9

Q

H¶

Q

D

Q

Q

H

Figure 8-1. Logic Diagram (Positive Logic) for the SN74HCS595

8.2 Feature Description

8.2.1 Balanced CMOS 3-State Outputs

This device includes balanced CMOS 3-State outputs. The three states that these outputs can be in are driving

high, driving low, and high impedance. The term "balanced" indicates that the device can sink and source similar

currents. The drive capability of this device may create fast edges into light loads so routing and load conditions

should be considered to prevent ringing. Additionally, the outputs of this device are capable of driving larger

currents than the device can sustain without being damaged. It is important for the output power of the device

to be limited to avoid damage due to overcurrent. The electrical and thermal limits defined in the Absolute

Maximum Ratings must be followed at all times.

When placed into the high-impedance mode, the output will neither source nor sink current, with the exception of

minor leakage current as defined in the Electrical Characteristics table. In the high-impedance state, the output

voltage is not controlled by the device and is dependent on external factors. If no other drivers are connected

to the node, then this is known as a floating node and the voltage is unknown. A pull-up or pull-down resistor

can be connected to the output to provide a known voltage at the output while it is in the high-impedance state.

The value of the resistor will depend on multiple factors, including parasitic capacitance and power consumption

limitations. Typically, a 10 kΩ resistor can be used to meet these requirements.

Unused 3-state CMOS outputs should be left disconnected.

8.2.2 Balanced CMOS Push-Pull Outputs

This device includes balanced CMOS push-pull outputs. The term "balanced" indicates that the device can sink

and source similar currents. The drive capability of this device may create fast edges into light loads so routing

and load conditions should be considered to prevent ringing. Additionally, the outputs of this device are capable

SN74HCS595

SCLS803B – OCTOBER 2020 – REVISED MAY 2021

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