MCRF200 Microchip Technology Inc., MCRF200 Datasheet - Page 4

• Manufacturer Part Number: MCRF200
• Description: 125 Khz Microid? Passive Rfid Device
• Manufacturer: Microchip Technology Inc.

MCRF200
2.0
The device contains three major building blocks. They
are RF front-end, configuration and control logic, and
memory sections. The Block Diagram is shown on
page 1.
2.1
The RF front-end of the device includes circuits for
rectification of the carrier, V
high-voltage clamping. This section also includes a
clock generator and modulation circuit.
2.1.1
The rectifier circuit rectifies RF voltage on the external
LC antenna circuit. Any excessive voltage on the tuned
circuit is clamped by the internal circuitry to a safe level
to prevent damage to the IC.
FIGURE 2-1:
DS21219H-page 4
FUNCTION DESCRIPTION
RF Front-End
Modulated RF Signal
(across V
RECTIFIER – AC CLAMP
Modulation Signal
A
and V
MODULATION SIGNAL AND MODULATED SIGNAL
DD
B
)
Amplitude
(operating voltage) and
L
C
2.1.2
This circuit generates a Power-on Reset when the tag
first enters the reader field. The Reset releases when
sufficient power has developed on the V
allow correct operation.
2.1.3
This circuit generates a clock based on the carrier
frequency from the reader. This clock is used to derive
all timing in the device, including the baud rate and
modulation rate.
2.1.4
The device sends the encoded data to the reader by
AM-modulating the coil voltage across the tuned LC
circuit. A modulation transistor is placed between the
two antenna coil pads (V
on and off based on the modulation signal. As a result,
the amplitude of the antenna coil voltage varies with the
modulation signal. See Figure 2-1 for details.
V
V
A
B
MCRF200
Modulation
Transistor
Modulation
Signal
POWER-ON RESET
CLOCK GENERATOR
MODULATION CIRCUIT
¤ 2003 Microchip Technology Inc.
A
and V
B
). The transistor turns
DD
t
regulator to