u3280m ATMEL Corporation, u3280m Datasheet - Page 6

• Manufacturer Part Number: u3280m
• Description: Transponder Interface For Microcontroller U3280m
• Manufacturer: ATMEL Corporation

4. U3280M Signals and Timing
Figure 4-1.
Figure 4-2.
4.1
4.2
6
Digital Output of the Gap-detection Stage (NGAP)
Wake-up Signal
Field clock FC
Power
management
Gap detection and battery to field switching
U3280M
Coil inputs
NGAP
Coil inputs
MOD
1. edge used as wakeup signal
Modulation
GAP and Modulation Timing
V
Battery supply
FDON
NGAP = 0: gap detected/no field
NGAP = 1: field detected
Note:
If a field is applied at the coil of the transponder interface, the microcontroller can be woken up
with the wake-up signal at the NGAP pin. For that purpose, the NGAP pin must be connected to
an interrupt input of the microcontroller. A high level at the NGAP output indicates an applied
field and can be used as a wake-up signal for the microcontroller via an interrupt. The wake-up
signal is generated if power management switches to field supply. The field-detection stage of
the power management has lowpass characteristics to avoid generating wake-up signals and
unnecessary switching between battery and field supply in case of interferences at the coil
inputs.
No amplifier is used in the gap-detection stage. A digital Schmitt trigger evaluates the rectified and
smoothed coil voltage.
V
CMS
t
BFS
Coil supply if automatically power management is enabled
V
CD
V
CU
t
FGAP1
V
V
coil-peak
coil-peak
t
FGAP0
= V
= V
FDoff
FDon
t
FBS
V
FDOFF
supply
Battery
4688D–RFID–03/07