LNBK20
LNB supply and control voltage regulator (parallel interface)
Feature summary
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Complete interface for two LNBs remote supply
and control
LNB selection and stand-by function
Built-in tone oscillator factory trimmed at
22KHz
Fast oscillator start-up facilitates DiSEqC
TM
encoding
Two supply inputs for lowest dissipation
Bypass function for slave operation
LNB short circuit protection and diagnostic
Auxiliary modulation input extends flexibility
Cable length compensation
Internal over temperature protection
Backward current protection
PowerSO-20
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Description
Intended for analog and digital satellite receivers,
the LNBK is a monolithic linear voltage regulator,
assembled in PowerSO-20 and SO-20,
specifically designed to provide the powering
voltages and the interfacing signals to the LNB
downconverter situated in the antenna
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via the coaxial cable. It has the same functionality
of the LNBP1X and LNBP20 series, at a reduced
output current capability. Since most satellite
receivers have two antenna ports, the output
voltage of the regulator is available at one of two
logic-selectable output pins (LNBA, LNBB). When
the IC is powered and put in Stand-by (EN pin
LOW), both regulator outputs are disabled to
allow the antenna downconverters to be
supplied/controlled by others satellite receivers
sharing the same coaxial lines. In this occurrence
the device will limit at 3 mA (max) the backward
current that could flow from LNBA and LNBB
output pins to GND. (See continuous description).
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SO-20
Order code
Packages
Part number
PowerSO-20
LNBK20
February 2007
LNBK20PD-TR
Rev. 8
SO-20
LNBK20D2-TR
Tape & Reel
1/25
www.st.com
25
Packaging
LNBK20
Contents
1
2
3
4
5
6
7
8
9
Description (continued) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Typical application schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
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2/25
LNBK20
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
CC1
and V
CC2
. They must be powered
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
the DiSEqC
TM
protocols
(a)
.
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
off
determined by the capacitor
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
on
=1/15t
off
(typ.) and OLF goes
in HIGH IMPEDANCE. If the overload is still present, the protection circuit will cycle again
through t
off
and t
on
until the overload is removed. Typical t
on
+t
off
value is 1200ms when a
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.
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a. External components are needed to comply to level 2.x and above (bidirectional) DiSEqC
TM
bus hardware
requirements. DiSEqC
TM
is a trademark or EUTELSAT.
3/25
Pin configuration
LNBK20
2
Figure 1.
Pin configuration
Pin connections (top view)
PowerSO-20
SO-20
Table 1.
SYMBOL
Pin description for PowerSO-20
NAME
FUNCTION
PIN NUMBER vs SALES TYPE (LNBP)
20CR 20PD 10SP 11SP 12SP 13SP 14SP 15SP 16SP
V
CC1
15V to 27V supply. It is
Supply input
automatically selected
1
when V
OUT
= 13 or 14V
22V to 27V supply. It is
Supply input
automatically selected
2
when V
OUT
= 18 or 19V
V
CC2
LNBA
See truth table voltage
and port selection. In
stand-by mode this port
Output port
is powered by the MI
pin via the internal
bypass switch
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EN
OSEL
GND
V
SEL
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Output
voltage
Logic control input: see
selection:13 truth table
or 18V (typ)
Port enable
Port
selection
Logic control input: see
truth table
Logic control input: see
truth table
Circuit ground. It is
internally connected to
the die frame
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1
2
2
3
3
4
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1
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1
1
1
2
2
2
3
3
3
3
3
3
3
4
5
4
4
4
4
4
4
4
5
7
6
7
1
10
11
20
5
9
5
NA
5
NA
5
NA
5
NA
5
NA
5
NA
Ground
8
6
6
6
6
6
6
6
4/25
LNBK20
Table 1.
SYMBOL
Pin configuration
Pin description for PowerSO-20
PIN NUMBER vs SALES TYPE (LNBP)
NAME
FUNCTION
20CR 20PD 10SP 11SP 12SP 13SP 14SP 15SP 16SP
ENT
22KHz tone Logic control input: see
enable
truth table
Timing capacitor used
by the dynamic
overload protection.
Typical application is
4.7µF for a 1200ms
cycle
External modulation
input. Needs DC
decoupling to the AC
source. if not used, can
be left open.
Logic control input: see
truth table
Logic output (open
collector). Normally in
HIGH IMPEDANCE,
goes LOW when
current or thermal
overload occurs
9
13
7
7
7
7
7
7
7
CEXT
External
capacitor
10
14
8
8
8
8
8
8
8
EXTM
External
modulator
11
15
NA
NA
NA
9
NA
9
9
LLC
Line length
compens.
(1V typ)
12
16
NA
NA
9
NA
OLF
Over load
flag
13
17
NA
9
MI
In stand-by mode, the
voltage on MI is routed
Master input to LNBA pin. Can be
left open if bypass
function is not needed
See truth tables for
Output port voltage and port
selection
14
LNBB
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18
19
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NA
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NA
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NA
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9
NA
10
10
10
NA
NA
NA
NA
NA
15
10
NA
NA
NA
NA
NA
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