TDA9889 查看數據表（PDF） - Philips Electronics

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TDA9889

DVB selective AGC amplifier

Philips Electronics 

Philips Semiconductors

DVB selective AGC amplifier

Product specification

TDA9888TS; TDA9889TS

PINNING

SYMBOL PIN

DESCRIPTION

S0

1 logic switch S0 input (frequency

select)

REF

2 4 MHz crystal or reference input

S2

3 logic switch S2 input (AGC select)

LFS

4 loop filter synthesizer PLL

LFLP

5 loop filter low-pass control PLL

AGC

6 AGC control voltage input

LIF1

7 low IF differential output 1

LIF2

8 low IF differential output 2

TADJ

9 tuner AGC TakeOver Point (TOP)

adjustment

TAGC

10 tuner AGC output

TAGCEXT 11 external tuner AGC voltage input

VP

12 supply voltage (+5 V)

S1

13 logic switch S1 input (frequency

select)

GND

14 ground supply

IF1

15 IF differential input 1

IF2

16 IF differential input 2

handbook, halfpage

S0 1

16 IF2

REF 2

15 IF1

S2 3

14 GND

LFS 4

13 S1

TDA9888TS

LFLP 5 TDA9889TS 12 VP

AGC 6

11 TAGCEXT

LIF1 7

10 TAGC

LIF2 8

9 TADJ

MHC093

Fig.2 Pin configuration.

FUNCTIONAL DESCRIPTION

Figure 1 shows the simplified block diagram of the device.

The integrated circuit contains the following functional

blocks:

1. Gain controlled IF amplifier

2. Tuner AGC

3. Reference generation

4. Synthesizer for downconversion

5. Downconversion and complex filtering

6. Tracking low-pass filter with reference control

7. Low IF differential output stage

8. Logic control

9. Internal voltage stabilizer.

Gain controlled IF amplifier

The IF amplifier consists of three AC-coupled differential

stages. Gain control is performed by emitter degeneration.

Total gain control range is 70 dB (typ.). The differential

input impedance is typical 2 kΩ in parallel with 3 pF.

Tuner AGC

The tuner AGC is realized by a TakeOver Point (TOP)

network and a peak-level detector. The threshold level of

the peak detector can be adjusted by an external

potentiometer connected to pin TADJ. For IF signals

above this threshold the level detector provides a

discharge current to pin TAGC. An additional current

source is internally connected to this pin providing charge

current to the external tuner AGC capacitor. For IF signals

of 8 dB below the threshold voltage this current will be

increased by a factor of approximately 40 for faster AGC

reaction. The ratio of discharge to charge current is

normally approximately 2000 and approximately 50 for

fast mode.

For use of the device in different applications the charge

current can be switched off, for hybrid applications the

signal at pin TAGCEXT can be fed via a transmission gate

to pin TAGC (TDA9888TS; TDA9889TS combined with

analog IF), controlled by the 3-state input pin S2. With an

activated transmission gate all internal currents are off.

In the event that the tuner AGC is not needed (e.g. TAGC

from channel decoder or from an analog IF in hybrid

chassis), pin TADJ should be left open-circuit and

therefore all internal AGC currents will be switched off.

2004 Nov 02

5

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