LNBP16 STMicroelectronics, LNBP16 Datasheet - Page 3

• Manufacturer Part Number: LNBP16
• Description: LNB SUPPLY AND CONTROL VOLTAGE REGULATOR (PARALLEL INTERFACE)
• Manufacturer: STMicroelectronics

LNBP20 / LNBP1X series
Description (continued)
1
Description (continued)
For slave operation in single dish, dual receiver systems, the bypass function is
implemented by an electronic switch between the Master Input pin (MI) and the LNBA pin,
thus leaving all LNB powering and control functions to the Master Receiver. This electronic
switch is closed when the device is powered and EN pin is LOW.
The regulator outputs can be logic controlled to be 13 or 18 V (typ.) by mean of the VSEL
pin for remote controlling of LNBs. Additionally, it is possible to increment by 1V (typ.) the
selected voltage value to compensate the excess voltage drop along the coaxial cable (LLC
pin HIGH).
In order to reduce the power dissipation of the device when the lowest output voltage is
selected, the regulator has two Supply Input pins V
and V
. They must be powered
CC1
CC2
respectively at 16V (min) and 23V (min), and an internal switch automatically will select the
suitable supply pin according to the selected output voltage. If adequate heatsink is
provided and higher power losses are acceptable, both supply pins can be powered by the
same 23V source without affecting any other circuit performance.
The ENT (Tone Enable) pin activates the internal oscillator so that the DC output is
modulated by a ±0.3 V, 22KHz (typ.) square wave. This internal oscillator is factory trimmed
within a tolerance of ±2KHz, thus no further adjustments neither external components are
required.
A burst coding of the 22KHz tone can be accomplished thanks to the fast response of the
ENT input and the prompt oscillator start-up. This helps designers who want to implement
TM
(a)
the DiSEqC
protocols
.
In order to improve design flexibility and to allow implementation of newcoming LNB remote
control standards, an analogic modulation input pin is available (EXTM). An appropriate DC
blocking capacitor must be used to couple the modulating signal source to the EXTM pin.
When external modulation is not used, the relevant pin can be left open.
Two pins are dedicated to the overcurrent protection/monitoring: CEXT and OLF. The
overcurrent protection circuit works dynamically: as soon as an overload is detected in
either LNB output, the output is shut-down for a time t
determined by the capacitor
off
connected between CEXT and GND. Simultaneously the OLF pin, that is an open collector
diagnostic output flag, from HIGH IMPEDANCE state goes LOW.
After the time has elapsed, the output is resumed for a time t
=1/15t
(typ.) and OLF goes
on
off
in HIGH IMPEDANCE. If the overload is still present, the protection circuit will cycle again
through t
and ton until the overload is removed. Typical t
+t
value is 1200ms when a
off
on
off
4.7µF external capacitor is used.
This dynamic operation can greatly reduce the power dissipation in short circuit condition,
still ensuring excellent power-on start up even with highly capacitive loads on LNB outputs.
The device is packaged in PowerSO-20 for surface mounting. When a limited functionality in
a smaller package matches design needs, a range of cost-effective PowerSO-10 solutions
is also offered. All versions have built-in thermal protection against overheating damage.
TM
a. External components are needed to comply to level 2.x and above (bidirectional) DiSEqC
bus hardware
TM
requirements. DiSEqC
is a trademark or EUTELSAT.
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