TUA6024-2 Infineon Technologies Corporation, TUA6024-2 Datasheet - Page 16

• Manufacturer Part Number: TUA6024-2
• Description: 2 Band Tv Tuner Mixer-oscillator-pll With Balanced If-amplifier
• Manufacturer: Infineon Technologies Corporation

TUA6024-2
Functional Description
control bits T0 = 1 and T1 = 0. Here it should be noted, however, that the tuning
voltage can alter over a long period in the high-impedance state as a result of
self-discharge in the peripheral circuitry. TUNE may be switched off by the con-
trol bit OS to allow external adjustments.
If the VCO is not oscillating the PLL locks to a tuning voltage of 33 V .
By means of the control bits CP, CM, T0 and T1 the pump current can be
switched between four values by software. This programmability permits alter-
ation of the control response time of the PLL in the locked-in state. In this way
different VCO gains can be compensated, for example.
The software-switched ports PLOW, PMID and PHIGH are general-purpose
open-collector outputs. The test bits T0 = 0 and T1 = 1 switches the test signals
f
(i.e.f
/ 64) and f
(divided input signal) to PLOW and PMID respec-
ref
XTAL
div
tively.
The lock detector resets the lock flag FL if the width of the charge pump current
pulses is wider than the period of the crystal oscillator (i.e. 250 ns). Hence, if FL
= 1, the maximum deviation of the input frequency from the programmed fre-
quency is given by
f =
I
(K
/ f
) (C1+C2) / (C1C2)
P
VCO
XTAL
where I
is the charge pump current, K
the VCO gain, f
the crystal oscil-
P
VCO
XTAL
lator frequency and C1, C2 the capacitances in the loop filter (
see Figure 4-2 Evalu-
). As the charge pump pulses at i.e. 62.5
ation Board, low phase noise application on page 20
kHz (= f
), it takes a maximum of 16 s for FL to be reset after the loop has lost
ref
lock state.
Once FL has been reset, it is set only if the charge pump pulse width is less than
250 ns for eight consecutive f
periods. Therefore it takes between 128 and
ref
144 s for FL to be set after the loop regains lock.
2
3.4.4
I
C-Bus Interface
2
Data is exchanged between the processor and the PLL via the I
C bus. The
clock is generated by the processor (input SCL), while pin SDA functions as an
input or output depending on the direction of the data (open collector, external
pull-up resistor). Both inputs have hysteresis and a low-pass characteristic,
2
which enhance the noise immunity of the I
C bus.
2
The data from the processor pass through an I
C bus controller. Depending on
their function the data are subsequently stored in registers. If the bus is free,
both lines will be in the marking state (SDA, SCL are HIGH). Each telegram
begins with the start condition and ends with the stop condition. Start condition:
SDA goes LOW, while SCL remains HIGH. Stop condition: SDA goes HIGH
while SCL remains HIGH. All further information transfer takes place during
SCL = LOW, and the data is forwarded to the control logic on the positive clock
edge.
The table ”Bit Allocation” (
) should be
see Table 5-4 Bit Allocation Read / Write on page 30
referred to the following description. All telegrams are transmitted byte-by-byte,
followed by a ninth clock pulse, during which the control logic returns the SDA
Wireless Components
3 - 9
Specification, July 2001