Motorola SSETM 5000 RF Detector D101, Power-Control IC Pcic U104, Pin Name Description

2-14 Theory of Operation: Transceiver Board

The initial design utilizes a cutoff frequency of 750 MHz, even though the actual design cutoff frequency is 488 MHz. The reasoning behind using a significantly higher cutoff frequency is due to the lower frequency response of realized circuits. The design tables used for the filter synthesis can be located in the Handbook of Filter Synthesis (Zverev, pp. 218–219), where θ = 47.0. This design was chosen because the attenuation at the stop band was the closest to the desired ratio for the SSE 5000 design.

The remote port harmonic filter consists of parts C709, C710, C711, C712, C713, L706, and L707. The antenna port harmonic filter consists of parts C716, C717, C718, C719, C720, L709, and L710. The filters are optimized for the impedance match seen for their respective ports and terminations.

NOTE: Capacitor C720 was changed to 2pF, because this value improved the radiated response of the radio with the antenna removed. Also, Capacitors C710 and C711 were increased in order to remove a spur located at the (2*LO)-IF frequency point (680.075 MHz), where LO is 450.0625 MHz – 73.35 MHz and IF is 73.35 MHz. Essentially, C710 and C711 decreased the cutoff frequency of the remote port harmonic filter.

2.4.3.7 RF Detector D101

Schottky diode D101 is used as a forward-power detector. Forward-coupled RF from the power amplifier is converted to a DC voltage. Detector output is a positive DC voltage, proportional to the amplitude of the RF signal at the input, and is applied to the ALC input of the PCIC.

2.4.3.8 Power-Control IC (PCIC) U104

The PCIC, U104, contains all of the digital, and most of the analog, circuits needed to control the transmitter power amplifier. Host control is through a 3-wire, smart SPI interface. Pin descriptions are shown in Table 2-8.

Table 2-8. Power Control IC (U104) Pin Descriptions

Pin	Name	Description
1	RFIN	Detector voltage input to ALC
2	T1	Test point
3	CI	External capacitor for integrator time constant
4	INT	Integrator output; control voltage to amplifiers
5	CJ	External capacitor for PA rise and fall times
6, 7	VL, CL	External capacitor for PA rise and fall times
8	GND1	Ground
9	F168	Reference clock input, 2.1 MHz
10, 13	QX, CQX	External capacitor for voltage multiplier
11, 12	Q, CQ	External capacitor for voltage multiplier
14	V10	Voltage multiplier output
15	VG	Internal band-gap reference voltage
16	V45	Regulated 4.5 Vdc output
17	V5EXT	Power supply input for internal voltage regulator

November 11, 2004 6881094C12-A