The dissipated die power is quasi constant over a significant supply voltage range as
shown below (mode 50 mW selected):
Figure 18.
Power = f ( Vdd )
5,40E-02
5,30E-02
5,20E-02
5,10E-02
5,00E-02
4,90E-02
4,80E-02
2
2,2
2,4
2,6
2,8
3
3,2
3,4
3,6
3,8
VDD
Power = f ( Vdd)
Note:
This function is useless for navigation and click modes.
Power Management
Sleep Mode (<10 µA)
Reset high
Standby Mode
Power consumption can be reduced in several ways:
(<10 µA Providing SPI
Bus not Accessed)
•
•
By switching off the FingerChip sensor.
By programming a standby mode by writing 00001xx in the MODCTRL register
(STANDBY mode set and oscillator stopped.) Bit b6 (HEAT) of the HEATCTRL
register must be turned to ‘0’ when programming standby mode.
Acquisition Mode
Current Consumption
Static Current Consumption
When the SPI bus is not used, only the analog part of the circuit consumes power at
around 4 mA.
Dynamic Current
Consumption
When the clock is running, the digital sections also consume current. With a 30 pF load
at 16 MHz, the power consumption is approximately 4.5 mA on the VDD pins.
32
AT77C105A [Preliminary]
5419A–BIOM–01/05
ATMEL [ ATMEL ]
