TDA6508 Datasheet, PDF (3/42 Pages) NXP Semiconductors – 3-band mixer/oscillator and PLL for terrestrial tuners

Philips Semiconductors
3-band mixer/oscillator and PLL for
terrestrial tuners
Product specification
TDA6508; TDA6508A;
TDA6509; TDA6509A
1 FEATURES
• Single-chip 5 V mixer / oscillator and synthesizer for TV,
VCR tuners, DVD-R and PC TV.
• I²C bus protocol compatible with 3.3 V and 5 V
microcontrollers
– Address with 4 data bytes transmission (I²C-bus
‘write’ mode)
– Address with 1 status byte (I²C-bus ‘read’ mode)
– 4 independent I²C-bus addresses.
• 5 Positive-channel Metal Oxide Semiconductor (PMOS)
output ports
– 3 buffers for band selection (20 mA)
– 2 buffers for general purpose, e.g. FM sound trap
(5 mA).
• 33 V tuning voltage output
• In-lock flag
• 5-step analog-to-digital converter (3 bits in I²C-bus
mode)
• 15-bit programmable divider
• Programmable reference divider ratio (64, 80 or 128)
• Programmable charge-pump current (20 or 100 µA)
• Balanced mixer with a common emitter input for LOW
band (single input)
• Balanced mixer with a common emitter input for MID
band (balanced input)
• Balanced mixer with a common base input for HIGH
band (balanced input)
• 2-pin asymmetrical oscillator for LOW band
• 2-pin symmetrical oscillator for MID band
• 2-pin symmetrical oscillator for HIGH band
• External 4-pin IF filter between mixer output (medium
impedance) and IF amplifier input (high impedance)
• Weak signal booster (I²C controlled switchable gain
amplifier)
• Low power
• Low radiation
• Small size
• TDA6508; TDA6509: symmetrical IF amplifier output to
drive a SAW filter (1.25 kΩ)
• TDA6508A; TDA6509A: single-ended IF amplifier to
drive low ohmic load (75 Ω).
2 APPLICATIONS
• 3-band tuner for terrestrial TV, DVD-R, VCR and PC TV.
3 GENERAL DESCRIPTION
This device is a programmable 3-band mixer oscillator and
synthesizer intended for LOW, MID and HIGH band TV
and VCR tuners. It has three double balanced mixers and
three oscillators for the LOW, MID and HIGH band
respectively, a PLL synthesizer, and an IF amplifier. There
are four package variants: TDA6508, TDA6509,
TDA6508A and TDA6509A. Versions TDA6508; TDA6509
have a symmetrical IF amplifier; versions TDA6508A;
TDA6509A have an asymmetrical IF amplifier, (see Fig.1).
The common output of all three mixers can be connected,
via two output pins, to an external IF filter to enable
shunted IF bandpass and/or serial filtering for improved
signal handling. Two input pins are available for
connecting the output of the external filter to the input of
the IF amplifier. The mixer output has an impedance
of 300 Ω. The IF amplifier input has an impedance
of 2.5 kΩ (5 pF).
The overall gain of the tuner can be increased at low signal
amplitude conditions to improve TV reception by activating
a weak signal booster via the I²C-bus.
There are five open-drain PMOS output ports; each port
has a different drive capability. I²C-bus bit P0 enables
port P0 (20 mA drain current) and the LOW band mixer
oscillator. Bit P1 enables port P1 (20 mA drain current)
and the MID band mixer oscillator. When ports P0 and P1
are both disabled, the HIGH band mixer oscillator is
enabled. Bit P2 enables port P2 (20 mA drain current).
Bit P3 enables port P3 (5 mA drain current) for general
use, and bit P4 enables port P4 (5 mA drain current) for
general use, and is also combined with the ADC input.
When the ports are used, the sum of the drain currents
must be limited to 30 mA.
The PLL synthesizer comprises a 15-bit programmable
divider, a crystal oscillator, programmable reference
divider, phase comparator (phase/frequency detector)
combined with a charge-pump which drives an internal
tuning amplifier and an output at pin CP. The CP signal
current can be integrated by connecting an external RC
2005 Mar 25
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