AZT71_1301 Datasheet, PDF (6/14 Pages) Arizona Microtek, Inc – Programmable Capacitive Tuning IC

Arizona Microtek, Inc.
AZT71
Programmable Capacitive Tuning IC
PROGRAMMING TO THE SHIFT REGISTER
Control word bits are inputted serially through the DA pin timed with the rising edge of the CLK pin. Figure 7 shows the
control word 11001100100 has been serially entered into the register. Note that bit0 is the 1^st bit to enter and bit10 is the
last. In the AZT71, bit0 does not affect the capacitance value but still must be included in the serial bit stream. For the
shift register, capacitors are selected when bits are active HIGH. For the AZT71 to read from the shift register, the CLK
pin must remain HIGH.
bit 0
bit 1
bit 2
bit 3
bit 4
bit 5
bit 6
bit 7
bit 8
bit 9 bit 10
DA
bit 0
loaded 1^st
Register data
active when
CLK is high
CLK
t
Figure 7 - Shift register programming
WRITING DATA TO THE EEPROM
Once the desired capacitance value has been determined, the digital control word can be written or re-written into the
EEPROM. By storing the control word in the EEPROM, the customer is prevented from making adjustments from the
factory set programming data. This is accomplished within the AZT71 with internal pull-downs on the DA, PV, and CLK
pins. The detailed sequence for writing data to the EEPROM within the AZT71 is described in Table 6. Note that with
EEPROM, capacitors are selected when bits are active LOW.
Step
Table 6 – Data writing sequence for EEPROM
Action
1
Determine the desired capacitor control word with the operational power supply voltage and
desired oscillator conditions
2 Set the V_DD supply voltage to +5.0V
3 If EEPROM is not already erased, erase EEPROM (see ERASING THE EEPROM)
4 Read the current state of the EEPROM bits (see READING BACK FROM THE EEPROM)
5
Compare the desired control word to the stored EEPROM control word. Count the number of
differences so as to prevent double/redundant writing
6 One bit at a time, load the first desired control word bit (bit selection for EEPROM is active LOW)
7 Set the PV pin to +6V (≥5.6V, ≤6.1V) with the pulse and idle shown in timing diagram (Figure 10)
8
Progress through all necessary control word bits by repeating steps 5 & 6 until all bits are set to the
desired control word.
9 Verify the correct EEPROM contents by reading back the individual bits
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6
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Jan 2013, Rev 1.3