MC72000 Freescale Semiconductor, MC72000 Datasheet - Page 140

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

Freescale Semiconductor, Inc.
Applications Information
10.3 External Power Amplifier Enable
The External Power Amplifier Enable (EPAEN) bit, R6/15, can be used in two applications. It may serve
as a complementary driver to a dual-port antenna. This is accomplished when External PA Enable Invert,
R3/10, is set to logic one. In this configuration, EPAEN assumes the inverted value of GPO, which is the
second driver for the antenna switch. EPAEN may also assist in Class 1 operation by setting bit R11/6 to
logic high. This setting allows the MC72000 to drive an external power amplifier. Setting bits R11/6 and
R3/10 to zero disables EPAEN.
10.4 External Power Amplifier DAC
The Bluetooth specification for Class 1 Power implementation requires power control from 4.0 dBm (or
less) to 20 dBm (max) power. The MC72000 external power amplifier digital to analog converter
(EPADRV) output (Pin K6) provides a voltage reference for power control of an external power amplifier
(PA), if desired. The EPADRV output is enabled when External PA DAC Enable (R11/7) is set to one.
Setting R11/7 to zero pulls the EPADRV output to ground. When enabled, the EPADRV output voltage is
controlled by the PA DAC setting (R3/5-0). The minimum EPADRV output voltage is 0 VDC and the
maximum output voltage is 3.2 VDC. The 6-bit resolution of the PA DAC setting corresponds to
approximately 50 mV/bit. When using a VCCRF < 3.2 Vdc, the maximum EPADRV output voltage is
reduced to VCCRF (i.e., the full-scale output of the PA DAC is referenced to 3.2 V). To obtain optimum
functionality of EPADRV with an external PA, this feature should be utilized with the External PA Enable.
Refer to Section 10, “Applications Information,” for additional usage information. The output of the
EPADRV, when enabled, is gated by the MC72000 sequence manager. During a sleep, idle, or RX cycle,
the output is set to zero volts. The programmed value of the output voltage is only achieved during an
active TX cycle as shown in Figure 30.
10.5 PIN Implementation of Antenna Switch
An alternative approach to using an RF switch is to utilize a PIN diode technique as shown in Figure 88.
When both PIN diodes are in the high resistance (i.e., un-biased) state, the transmitter is isolated from the
antenna and LNA input. Conversely, when both PIN diodes are in the low resistance (i.e., forward-biased)
state, the l/4 section appears as an open circuit from the transmitter output to the LNA input, and the
transmitter output is coupled directly to the antenna through the bandpass filter. For receive mode, GPO is
set low. For transmit mode, GPO is set high. Some advantages to this implementation include very low
current consumption while in receive or idle mode, moderate current consumption while in transmit mode,
high receiver isolation, and low cost.
140
MC72000 Advance Information Data Sheet
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