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.

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).

APPLICATIONS
• 3-band tuner for terrestrial TV, DVD-R, VCR and PC TV.