uaa3515a NXP Semiconductors, uaa3515a Datasheet - Page 12

• Manufacturer Part Number: uaa3515a
• Description: 900 Mhz Analog Cordless Telephone Ic
• Manufacturer: NXP Semiconductors

Philips Semiconductors
7.4
The crystal local oscillator and reference divider (see
Fig.5) provide the reference frequency for the RX and TX
PLLs. The 10-bit reference divider is programmed with
respect to the crystal frequency and the desired RX and
TX frequencies. The microcontroller operating frequency
of 4.096 MHz is derived from a 16.384 MHz crystal
frequency. The clock divider ratio can be programmed to
1, 2, 2.5, 4 or to 128; ratio 128 is chosen in sleep mode to
save current in the microcontroller section. Clock output
(pin CLKOUT) is an emitter follower output.
The 16-bit TX counter is programmed for the desired
transmit channel frequency. Similarly, the 16-bit RX
counter is programmed for the desired local oscillator
frequency. The divider counter comprises a 6-bit prescaler
with division ratios (R) from 64 to 127, and a 10-bit CMOS
divider with division ratios (C) from 8 to 1023. The full
counter provides division ratios from 512 to 65535.
Settings of RX and TX counters are calculated as follows:
(where M is the division ratio between VCO frequency and
the reference frequency).
2002 Sep 09
C = int
R = M
900 MHz analog cordless telephone IC
Synthesizer
----- -
64
M
C
64
12
7.4.1
Given:
We have:
and
VCOs and variable capacitance diodes are integrated.
Resonance inductors are shared between bonding wires,
leadframe of the package and external inductors. Costs
can be reduced by etching external inductors directly onto
the printed-circuit board.
An on-chip selectable voltage doubler is provided to
enable a larger tuning range of both VCOs. The phase
detectors have current drive type outputs with selection
possibilities between 400 and 800 A.
RF input frequency f
VCO RX f
f
VCO TX f
Internal comparison frequency = 20 kHz
(f
Reference divider = 512 (1000000000)
C RX = 697 (1010111001) and R RX = 7 (000111)
C TX = 723 (1011010011) and R TX = 8 (001000)
M RX
M TX
IF
XTAL
= 10.7 MHz
= 10.24 MHz)
C
=
=
ALCULATION EXAMPLE
925.6 10
----------------------------- -
892.3 10
----------------------------- -
VCO(TX)
VCO(RX)
20 10
20 10
= 925.6 MHz
= 892.3 MHz
3
3
6
6
i(RF)
=
=
46280
44615
= 903 MHz
Product specification
UAA3515A