TDA6508; TDA6508A; TDA6509; TDA6509A

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 Ohm. The IF amplifier input has an impedance of 2.5 kOhm (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 loop filter between pin CP and pin VTUNE as shown in Fig.27. The tuning amplifier can supply up to 33 V (max.) at pin VT for controlling any of the internal oscillators via external tank circuits. The phase comparator can operate at 62.5, 50 or 31.25 kHz with a 4 MHz crystal, depending on the reference divider ratio of either 64, 80 or 128; see Table 4. An externally sourced signal having a frequency between 3.58 MHz and 4.43 MHz can be used as a reference frequency for the internal crystal oscillator at any of the reference divider ratios.

In test mode, port P3 will output either half the crystal reference frequency ( 1/2 f_ref ) or half the reference divider frequency ( 1/2 f_div ); see Table 5.

The device can be controlled according to the I²C-bus format; see Table 1. The in-lock flag bit FL is set to logic 1 when the PLL is locked. This flag is read from the status byte on pin SDA during a READ operation; see Table 6 and Table 7.

Automatic frequency control is provided using an internal Analog-to-Digital Converter controlled by the voltage on pin ADC. The ADC code is read during a READ operation; see Table 8.

The device requires to be addressed by five sequential serial bytes (including the address byte) via the I²C-bus to set the crystal oscillator frequency, program the five ports and to set the charge-pump current; see Table 1. The address byte can have one of four possible device addresses which are selected by applying a specific voltage to pin AS; see Table 3.

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 uA)
• 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 kOhm)
• TDA6508A; TDA6509A: single-ended IF amplifier to drive low ohmic load (75 Ohm).

Products/packages

Products in the above table are all in production. Some variants are discontinued; click here for information on these variants.

Pricing/ordering/availability

Applications

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

Related applications
50-60 Hz CRT integrated DTV (TV210D)
PCI analog stereo TV receiver

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