MC72000 Freescale Semiconductor, MC72000 Datasheet - Page 34

• Manufacturer Part Number: MC72000
• Description: Integrated Bluetooth Radio
• Manufacturer: Freescale Semiconductor

Radio Functional Description
The mixer delivers approximately 15.8 dB of voltage gain and 22 dB of image rejection.
The mixer is enabled approximately 150 µs after the assertion of the RTXEN pin when programmed for
Receive mode. It is disabled immediately after the deassertion of the RTXEN pin or during any Idle or
Transmit mode.
6.3.3 Bandpass Filter (BPF)
The 6.0 MHz bandpass filter is used to block undesired channels. The filter is self-adjusting and is
calibrated during each receive cycle, based on an internally generated 6.0 MHz signal. The gain of the
filter is fixed at 4.0 dB.
The nominal pass band for the filter is 720 kHz. This deliberately low pass band can cause significant
intersymbol interference (ISI) issues for a GFSK modulated signal with a 1 Mbit/s data rate. The
advantages are increased sensitivity, adjacent channel interference performance, and ease of manufacture.
Due to this low pass band, a digitally implemented decoder scheme is utilized to eliminate ISI. This is
referenced as the JD/MLSE and is incorporated into all Motorola Bluetooth basebands.
The BPF is enabled approximately 10 µs after the assertion of the RTXEN pin while programmed for
Receive mode and automatic tuning is complete after approximately 140 µs. It is disabled immediately
after the deassertion of the RTXEN pin or during any Idle or Transmit mode.
6.3.4 Limiter with Received Signal Strength Indicator (RSSI)
The received signal strength indicator (RSSI) is integrated into the limiter. The RSSI ADC converts the
RSSI current into a 4-bit digital signal. When the RSSI enable (R4/6) and RSSI Read Enable (R9/8) are
both set, the 4-bit RSSI conversion value can be read from the MC72000 Radio Register Map (R29/3-0)
while in Idle mode. The RSSI is updated approximately 40 µs after receiving the first bit in a receive cycle.
Enabling RSSI will result in additional current consumption as noted in the Receiver AC Electrical
Specifications shown in Table 8. Figure 8 shows the RSSI conversion value versus the RF level input to
the LNA at various temperatures. Figure 9 shows the RSSI conversion versus the RF level at different
power supplies.
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Figure 7. High-Side and Low-Side Mixer Injection
Freescale Semiconductor, Inc.
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MC72000 Advance Information Data Sheet
Go to: www.freescale.com
Low-side LO injection (R2/11 = 0)
High-side LO injection (R2/11=1)
Image
RF
Preliminary
LO
LO
Image
RF
MOTOROLA