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August ’01
Chapter 2. Electrical Description
2.11.2 Trimming EEPROM Programming
Using the known typical parameters of the external components, IC input capacitance (CRF1,
CRF2, CRF3) and the result from first resonance frequency measurement a necessary parallel
capacitor can be calculated. From this it can be determined which internal trimming capaci-
tors must be switched on.
After clocking in the test number of the relating trimming circuit (PTx14, PTx24, PTx34), the
8-bit Trimming Byte is shifted (see Figure 27). LSB is shifted first, which represents the
smallest capacitor (CT1). A low bit switches off and a high bit switches on a capacitor. The
programming mode is entered with TEN = high. Programming starts when TEN is ramped-
up to VPP level. The test mode is left with TEN=low.
Result of programming process should be checked by an additional Resonance Frequency
Measurement and Trimming EEPROM Programming should be repeated if necessary.
Figure 27: Timing Diagram for Test Mode PTx14
2.11.3 Modulation Frequency Check
During LF Transmission Mode a Frequency Shift Keying signal is transmitted. The Reso-
nance Frequency of the trimmed Resonant Circuit is the representation of a Low Bit (fL). The
High Bit is represented by the lower High Bit Frequency (fH), achieved by switching on the
Modulation Capacitor (CM). For checking this frequency Test Mode PTx16 is provided.
The test flow is according to Figure 24 with the exception that test number is 16hex.
1
1
2 3 4 5
LSB
VBAT
TDAT
TCLK
TEN
2 3
tPRG
LSB
tfVPP
trVPP
VBAT
VPP
6
4
WDEEN
3DTMOD14.DRW
TEST MODE
PTx14
5 6 7 8
TRIMMING BYTE