74HC4060PW datasheet(11/12 Pages) PHILIPS

11 / 12 page

December 1990

Philips Semiconductors

Product speciﬁcation

14-stage binary ripple counter with oscillator

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.

handbook, halfpage

MBA333

0123

456

(mA/V)

(V)

max.

min.

typ.

Fig.8

Typical forward transconductance gfs as a

function of the supply voltage VCC at

Tamb =25 °C.

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.

RC OSCILLATOR

Fig.10 Example of a RC oscillator.

Typical formula for oscillator frequency:

osc

2.5

--------------------------------

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 k

Ω< Rt < 1 MΩ.

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

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