PCA2000USLASHAB datasheet(12/28 Pages) NXP

12 / 28 page

PCA2000_2001_5

Product data sheet

Rev. 05 — 11 November 2008

12 of 28

NXP Semiconductors

PCA2000; PCA2001

32 kHz watch circuit with programmable adaptive motor pulse

7.9 Checking memory content

The stored data of the OTP array can be checked bit wise by measuring the supply

current. The array word is selected by the instruction state and the bit is addressed by the

shift register.

To read a word, the word is ﬁrst selected (td =t1), and a logic 1 is written into the ﬁrst cell

of the shift register (td =t3). This logic 1 is then shifted through the entire shift register

(td =t2), so that it points with each clock pulse to the next bit.

If the addressed OTP cell contains a logic 1, a 30 k

Ω resistor is connected between V

and VSS, which increases the supply current accordingly.

Figure 8 shows the supply voltage modulation for reading word B, with the corresponding

supply current variation for word B = 110101 (sequence: ﬁrst MSB and last LSB).

(1)

Fig 8.

Supply voltage modulation and corresponding supply current variation for

reading word B

VDD(nom)

VDD

VP(mod)

(1)

VSS

mgw357

IDD

t1 t1

VP(prog)(start)

tp(start)

VP(prog)(stop)

tp(stop)

∆I

30 k

Ω

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