ASAHI KASEI
[AK2570]
AK2570 consists of these circuit blocks as below.
Circuit block
Oscillator
VREF
T-SENSE
AD1
AD2
DA1,
AMP1
DA2,
AMP2
DA3, ALMOUT,
Comparator, ALM
Timing Generator
EEPROM
Register
Control
Power on Reset
Functional description
This circuit generates the standard clock that settles the timing for the sequence of the
internal circuit in “Self-operation mode (Ordinary mode)”.
This circuit generates the reference voltage for the A to D converter, the D to A converter
and the T-SENSE.
This circuit is the thermo-sensor, outputs the voltage corresponding to the ambient
temperature, i.e. the temperature to voltage converter, and transfers this output voltage to
AD2. Also it integrates the offset adjustment circuit that cancels the distribution.
The A to D converter encodes the input voltage at VPDIN-pin (the signal from the
monitor PD) to the 8bits digital data. It is possible to read the encoded data of monitor PD
signal (the reference data for RDA3) held in RVPD register and to set the alarm threshold
level for the degraded LD in “Training mode”.
The A to D converter encodes the T-SENSE output signal to the 8bits digital data. In
“Self- operation mode”, the encoded data of the ambient temperature detected by the
T-SENSE is converted to the EEPROM address and utilized for reading the temperature
characteristic data of the LD retained in the EEPROM. In “Training mode”, it is possible
to read the encoded data of the detected temperature held in RTMP register.
This block consists of the D to A converter and the Op-amp and controls the Bias- or the
Modulation- current for the LD. DA1 decodes the 8bits digital data held in RDA1 register
to the compensation voltage for the temperature drift of the LD. Inputting the ‘H’ level
signal to SHUTDN-pin makes that DAOUT1-pin outputs ‘0V (min.)’.
This block consists of the D to A converter and the Op-amp and controls the Bias- or the
Modulation- current for the LD. DA2 decodes the 8bits digital data held in RDA2 register
to the compensation voltage for the temperature drift of the LD. Inputting the ‘H’ level
signal to SHUTDN-pin makes that DAOUT2-pin outputs ‘0V (min.)’.
This block outputs the ‘H’ level alarm signal from ALM-pin in the case that the
monitoring PD signal becomes lower than the alarm threshold level retained in the
EEPROM and held in RDA3 register, and this case is caused by the aging degradation.
This memory is the non-volatile memory, has the capacity ‘Address 9bits × Data 16bits’
and retains the data as below,
1. The temperature compensation data for the LD (transferred to RDA1 and RDA2 registers)
and the alarm threshold level data for the degraded LD (transferred to RDA3 register)
corresponding to the ambient temperature (the output from the T-SNESE and AD2).
2. The trimming data for the T-SENSE offset and the ALMOUT timing.
This circuit temporarily stores the ambient temperature data (in RTMP register), the
temperature compensation data for the LD (in RDA1 and RDA2 registers), the alarm
threshold level data (in RDA3 register) and so on.
This circuit controls the internal circuit, e.g. registers, with the serial interface.
At ‘Power ON’, this circuit initializes the data in all registers (see p.9) and sets AK2570 in
“Self-operation mode”.
<MS0115-E-00>
3
2001/10