MCP2030A-I Datasheet, PDF (27/66 Pages) Microchip Technology – Three-Channel Analog Front-End Device

4.0 APPLICATION INFORMATION
The MCP2030 is a stand-alone 3-channel analog
front-end device for low frequency (LF) sensing and
bidirectional transponder applications. By connecting
three orthogonally placed LC resonant antennas to
the LC input pins, it can detect signals from all
directions (x, y and z).
The device draws more current when all channels are
enabled as compared to a single channel; therefore, it
is recommended to disable any unused channels by
setting Configuration Register 0 (Register 5-1).
The device’s high input sensitivity (as low as 1 mV_PP)
and ability to detect weakly modulated (as low as 8%)
input signals with its low power feature set, makes the
device suitable for various applications such as a low-
cost hands-free Passive Keyless Entry (PKE)
transponder, an LF Initiator sensor for Tire Pressure
Monitoring Systems (TPMS) and long-range access
control applications in the automotive and security
industries.
MCP2030
4.1 Battery Back-up and Batteryless
Operation
The device supports both battery back-up and
batteryless operation by the addition of external
components, allowing the device to be partially or
completely powered from the field.
Figure 4-1 shows an example of the external circuit for
the battery back-up.
Note:
Voltage on LCCOM combined with coil
input voltage must not exceed the maxi-
mum LC input voltage.
V_BAT
V_DD
D_BLOCK
D_LIM
C_POOL
D_FLAT1
L_X
Air Coil
R_LIM
C_X
L_Y
C_Y
L_Z
D_FLAT2
R_COM C_COM
LCX
LCY
LCZ
C_Z
LCCOM
Legend: C_COM = LCCOM charging capacitor.
C_POOL = Pool capacitor (or battery back-up capacitor), charges in field and powers device.
D_BLOCK = Battery protection from reverse charge.
Schottky for low forward bias drop.
D_FLAT = Field rectifier diodes.
D_LIM = Voltage limiting diode, may be required to limit V_DD voltage when in strong fields.
R_COM = LCCOM discharge path.
R_LIM = Current limiting resistor, required for air coil in strong fields.
FIGURE 4-1:
External Circuit Example for LF Field Powering and Battery Back-up Mode.
© 2005 Microchip Technology Inc.
DS21981A-page 27