Pin Descriptions
See
Figure 4
through
Figure 10
for input and output sche-
matics.
Pin 1 — f
MIN
:
A resistor from this pin to ground sets the free
run frequency of the LM1290. The free run frequency should
be set typically as:
f
MIN
= 0.85(f
MINLOCK
) − 2 kHz
where f
MINLOCK
is the minimum lock frequency required for
the application. The resistance required to set this frequency
is approximately:
For example, to find R
MIN
for VGA which has f
MINLOCK
=
31.469 kHz,
f
MIN
= 0.85(31.469 kHz) − 2 kHz = 24749
DRIVE output (pin 7) is latched high. V
CC
has to be reduced
to below approximately 2V to clear the latched condition, i.e.,
power must be turned off. See
Figure 7
for the input sche-
matic.
Pin 6 — FLYBACK:
Input pin for phase detector 2. For best
operation, the flyback peak should be at least 5V but not
greater than V
CC
. Any pulse width greater than 1.5 µs is ac-
ceptable. See
Figure 8
for the input schematic.
Pin 7 — H DRIVE:
This is an open-collector output which
provides the drive pulse for the high power deflection circuit.
The pulse duty cycle is controlled by pin 4. Polarity conven-
tion: Horizontal deflection output transistor is on when H
DRIVE OUT is low. See
Figure 9
for the output schematic.
Pin 8 — GND:
System ground. For best jitter performance,
all bypass capacitors should be connected to this pin via
short paths.
Pin 9 — PD2 FILTER:
The low-pass filter cap of between
0.01 µF to 1 µF for the output of phase detector 2 is con-
nected from this pin to pin 8 (GND) via a short path. A
smaller value increases the response.
Pin 10 — PHASE:
A DC control voltage applied to this pin
sets the phase of the flyback pulse with respect to the center
of H sync. See
Figure 10
for the input schematic.
Pin 11 — FVC FILTER:
A 1 µF capacitor is connected from
this pin to pin 8 (GND) via a short path.
Pin 12 — PD1 OUT/VCO IN:
Phase detector 1 has a gated
charge pump output which requires an external low-pass fil-
ter. For best jitter performance, the filter should be grounded
to pin 8 (GND) via a short path. If a voltage source is applied
to this pin, the phase detector is disabled and the VCO can
be controlled directly.
Pin 13 — V
REF
:
This is the decoupling pin for the internal
8.2V reference. It should be decoupled to pin 8 (GND) via a
short path with a cap of at least 470 µF. Do not load this pin.
Pin 14 — V
CC
:
12V nominal power supply pin. This pin
should be decoupled to pin 8 (GND) via a short path with a
cap of at least 47 µF.
Rounding to the closest standard 1% resistor gives R
MIN
=
21.5 kΩ.
Pin 2 — H/HV POLARITY:
A 0.1 µF capacitor is connected
from this pin to ground for detecting the polarity of H/HV sync
at pin 3. A low logic level at pin 2 indicates active-high H/HV
sync to pin 3, a high level indicates active-low. See
Figure 4
for the output schematic.
Pin 3 — H/HV SYNC:
This input pin accepts DC-coupled H
or composite sync of either polarity. For best noise immunity,
a resistor of 2 kΩ or less should be connected from this pin
to pin 8 (GND) via a short path. See
Figure 5
for the input
schematic.
Pin 4 — DUTY CYCLE:
A DC voltage applied to this pin sets
the duty cycle of the H DRIVE output (pin 7), with a range of
approximately 30% to 70%. 2V sets the duty cycle to ap-
proximately 50%. See
Figure 6
for the input schematic.
Pin 5 — X-RAY:
This pin is for monitoring CRT anode volt-
age. If the input voltage exceeds an internal threshold, H
Input/Output Schematics
DS012917-5
DS012917-4
FIGURE 5.
FIGURE 4.
5
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