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74HC4060DB

14-stage binary ripple counter with oscillator

Philips Electronics 

Philips Semiconductors

14-stage binary ripple counter with oscillator

Product specification

74HC/HCT4060

Fig.7

Test set-up for measuring forward

transconductance gfs = dio / dvi at vo is

constant (see also graph Fig.8);

MR = LOW.

14

handbookg, hfsalfpage

(mA/V)

12

10

MBA333

max.

typ.

8

min.

6

4

Fig.8

2

0

1

2

3

4

5

6

VCC (V)

Typical forward transconductance gfs as a

function of the supply voltage VCC at

Tamb = 25 °C.

RC OSCILLATOR

Fig.9

RC oscillator frequency as a function of

Rt and Ct at VCC = 2.0 to 6.0 V; Tamb = 25 °C.

Ct curve at Rt = 100 kΩ; R2 = 200 kΩ.

Rt curve at Ct = 1 nF; R2 = 2 × Rt.

Typical formula for oscillator frequency:

fosc = 2----.--5----×-----1R-----t--×-----C----t

Fig.10 Example of a RC oscillator.

TIMING COMPONENT LIMITATIONS

The oscillator frequency is mainly determined by RtCt, provided R2 ≈ 2Rt and R2C2 << RtCt. The function of R2 is to

minimize the influence of the forward voltage across the input protection diodes on the frequency. The stray capacitance

C2 should be kept as small as possible. In consideration of accuracy, Ct must be larger than the inherent stray

capacitance. Rt must be larger than the “ON” resistance in series with it, which typically is 280 Ω at VCC = 2.0 V, 130 Ω at

VCC = 4.5 V and 100 Ω at VCC = 6.0 V.

The recommended values for these components to maintain agreement with the typical oscillation formula are:

Ct > 50 pF, up to any practical value,

10 kΩ < Rt < 1 MΩ.

In order to avoid start-up problems, Rt ≥ 1 kΩ.

December 1990

11

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