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PDF LNBH221 Data sheet ( Hoja de datos )
| Número de pieza | LNBH221 | |
| Descripción | DUAL LNB SUPPLY AND CONTROL IC WITH STEP-UP CONVERTER AND I2C INTERFACE | |
| Fabricantes | STMicroelectronics | |
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LNBH221
DUAL LNB SUPPLY AND CONTROL IC
WITH STEP-UP CONVERTER AND I2C INTERFACE
s ALL THE FEATURES ARE THE SAME FOR
BOTH SECTION
s COMPLETE AND INDEPENDENT
INTERFACE BETWEEN LNBs AND
RELEVANT I2CTM BUS
s BUILT-IN DC/DC CONTROLLER FOR
SINGLE 12V SUPPLY OPERATION AND
HIGH EFFICIENCY (Typ. 93% @ 500mA)
s LNB OUTPUT CURRENT GUARANTEED UP
TO 500mA
s BOTH COMPLIANT WITH EUTELSAT AND
DIRECTV OUTPUT VOLTAGE
SPECIFICATION
s ACCURATE BUILT-IN 22KHz TONE
OSCILLATOR SUITS WIDELY ACCEPTED
STANDARDS
s FAST OSCILLATOR START-UP FACILITATES
DiSEqCTM ENCODING
s BUILT-IN 22KHz TONE DETECTOR
SUPPORTS BI-DIRECTIONAL DiSEqCTM 2.0
s SEMI-LOWDROP POST REGULATOR AND
HIGH EFFICIENCY STEP-UP PWM FOR
LOW POWER LOSS: Typ. 0.56W @ 125mA
s TWO OUTPUT PINS SUITABLE TO BYPASS
THE OUTPUT R-L FILTER AND AVOID ANY
TONE DISTORSION (R-L FILTER AS PER
DiSEqC 2.0 SPECs, see application circuit on
pag. 4)
s OVERLOAD AND OVER-TEMPERATURE
INTERNAL PROTECTIONS
s OVERLOAD AND OVER-TEMPERATURE I2C
DIAGNOSTIC BITs
s LNB SHORT CIRCUIT SOA PROTECTION
WITH I2C DIAGNOSTIC BIT
s +/- 4KV ESD TOLERANT ON INPUT/
OUTPUT POWER PINS
DESCRIPTION
Intended for analog and digital DUAL Satellite
STB receivers/SatTV, sets/PC cards, the
LNBH221 is a voltage regulator and interface IC,
assembled in POWER SO-36, specifically
designed to provide the power 13/18V, and the
22KHz tone signalling for two independent LNB
down converters or to a multiswitch box that could
be independently powered and set. In this applica-
tion field, it offers a complete solution with ex-
April 2004
PRELIMINARY DATA
PowerSO-36
tremely low component count, low power dissipa-
tion together with simple design and I2CTM stan-
dard interfacing.
BLOCK DIAGRAM
Gate
Sense
Vup
Vcc
Byp
SDA
SCL
ADDR
DSQIN
Step-up
Controller
Preregul.+
U.V.lockout
+P.ON res.
V Select
I²C Enable
TEN
LNBH221- section A
Linear Post-reg
+Modulator
+Protections
Diagn.
22KHz
Oscill.
Tone
Detector
VoTX
VoRX
EXTM
DETIN
DSQOUT
Gate
Sense
Vup
Vcc
Byp
SDA
SCL
ADDR
DSQIN
Step-up
Controller
Preregul.+
U.V.lockout
+P.ON res.
V Select
I²C Enable
TEN
LNBH221- section B
Linear Post-reg
+Modulator
+Protections
Diagn.
22KHz
Oscill.
Tone
Detector
VoTX
VoRX
EXTM
DETIN
DSQOUT
1/18
This is preliminary information on a new product now in development are or undergoing evaluation. Details subject to change without notice.
1 page  
LNBH221
APPLICATION INFORMATION
Basically, the LNBH221 includes two circuits that are completely independent. Each circuit can be
separately controlled and must have its independent external components. All the below specification
must be considered equal for each section.
This IC has a built in DC/DC step-up controller that, from a single supply source ranging from 8 to 15V,
generates the voltages (VUP) that let the linear post-regulator to work at a minimum dissipated power of
1W typ. @ 500mA load (the linear regulator drop voltage is internally kept at: VUP-VOUT=2V typ.). An
UnderVoltage Lockout circuit will disable the whole circuit when the supplied VCC drops below a fixed
threshold (6.7V typically). The internal 22KHz tone generator is factory trimmed in accordance to the
standards, and can be controlled either by the I2CTM interface or by a dedicated pin (DSQIN) that allows
immediate DiSEqCTM data encoding (*). When the TEN (Tone ENable) I2C bit it is set to HIGH, a
continuous 22KHz tone is generated on the output regardless of the DSQIN pin logic status.
The TEN bit must be set LOW when the DSQIN pin is used for DiSEqCTM encoding. The fully
bi-directional DiSEqCTM 2.0 interfacing is completed by the built-in 22KHz tone detector. Its input pin
(DETIN) must be AC coupled to the DiSEqCTM bus, and the extracted PWK data are available on the
DSQOUT pin (*). To comply to the bi-directional DiSEqCTM 2.0 bus hardware requirements an output R-L
filter is needed. The LNBH221 is provided with two output pins: the VOTX to be used during the tone
transmission and the VORX to be used when the tone is received. This allows the 22KHz Tone to pass
without any losses due to the R-L filter impedance (see DiSeqC 2.0 application circuit on page 5). In
DiSeqC 2.0 applications during the 22KHz transmission activated by DSQIN pin (or TEN I2C bit), the
VOTX pin must be preventively set ON by the TTX I2C bit and, both the 13/18V power supply and the
22KHz tone, are provided by mean
VOTX must be set to OFF by setting
of VOTX
the TTX
output. As soon as the tone transmission is expired, the
I2C bit to zero and the 13/18V power supply is provided to
the LNB
R-L filter
by
is
the
not
VORX pin through the
required (see DiSeqC
R-L filter. When the LNBH221 is
1.x application circuit on pag.5),
used in DiSeqC 1.x applications the
the TTX I2C bit must be kept always
to HIGH
enabled
so that, the VOTX
by DSQIN pin or by
output pin can
TEN I2C bit. All
provide both
the functions
the 13/18V power supply and the 22KHz tone,
of this IC are controlled via I2CTM bus by writing
6 bits on the System Register (SR, 8 bits). The same register can be read back, and two bits will report the
diagnostic status. When the IC is put in Stand-by (EN bit LOW), the power blocks are disabled.
When the regulator blocks are active (EN bit HIGH), the output can be logic controlled to be 13 or 18 V by
mean of the VSEL bit (Voltage SELect) for remote controlling of non-DiSEqC LNBs. Additionally, the
LNBH221 is provided with the LLC I2C bit that increase the selected voltage value (+1V when VSEL=0
and +1.5V when VSEL=1) to compensate for the excess voltage drop along the coaxial cable (LLC bit
HIGH). By mean of the LLC bit, the LNBH221 is also compliant to the American LNB power supply
standards that require the higher output voltage level to 19.5V (typ.) (instead of 18V), by simply setting the
LLC=1 when VSEL=1. 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. Also in this case, the VOTX output must be set ON during the tone transmission by setting the TTX bit
high. When external modulation is not used, the relevant pin can be left open. The current limitation block
is SOA type: if the output port is shorted to ground, the SOA current limitation block limits the short circuit
current (ISC) at typically 300mA or 200mA respectively for VOUT 13V or 18V, to reduce the power
dissipation. Moreover, it is possible to set the Short Circuit Current protection either statically (simple
current clamp) or dynamically by the PCL bit of the I2C SR; when the PCL (Pulsed Current Limiting) bit is
set to LOW, the overcurrent protection circuit works dynamically, as soon as an overload is detected, the
output is shut-down for a time TOFF, typically 900ms. Simultaneously the OLF bit of the System Register
is set to HIGH. After this time has elapsed, the output is resumed for a time TON=1/10TOFF (typ.). At the
end of TON, if the overload is still detected, the protection circuit will cycle again through TOFF and TON. At
the end of a full TON in which no overload is detected, normal operation is resumed and the OLF bit is
reset to LOW. Typical TON+TOFF time is 990ms and it is determined by an internal timer. This dynamic
operation can greatly reduce the power dissipation in short circuit condition, still ensuring excellent
power-on start up in most conditions. However, there could be some cases in which an highly capacitive
load on the output may cause a difficult start-up when the dynamic protection is chosen. This can be
solved by initiating any power start-up in static mode (PCL=HIGH) and then switching to the dynamic
mode (PCL=LOW) after a chosen amount of time. When in static mode, the OLF bit goes HIGH when the
current clamp limit is reached and returns LOW when the overload condition is cleared. This IC is also
5/18
5 Page 
LNBH221
THERMAL DESIGN NOTES
During normal operation, the LNBH221 device dissipates some power. At rated output current of 500mA
on each section output, the voltage drop on both linear regulators lead to a total dissipated power that is
typically 2W. The heat generated requires a suitable heatsink to keep the junction temperature below the
over-temperature protection threshold. Assuming a 45°C temperature inside the Set-Top-Box case, the
total Rthj-amb has to be less than 40°C/W.
While this can be easily achieved using a through-hole power package that can be attached to a small
heatsink or to the metallic frame of the receiver, a surface mount power package must rely on PCB
solutions whose thermal efficiency is often limited. The simplest solution is to use a large, continuous
copper area of the GND layer to dissipate the heat coming from the IC body.
Given for the PSO-20 package an Rthj-c equal to 2°C/W, a maximum of 38°C/W are left to the PCB
heatsink. This area can be the inner GND layer of a multi-layer PCB, or, in a dual layer PCB, an unbroken
GND area even on the opposite side where the IC is placed. In figure 4, it is shown a suggested layout for
the PSO-20 package with a dual layer PCB, where the IC exposed pad connected to GND and the square
dissipating area are thermally connected through 32 vias holes, filled by solder. This arrangement, when
L=40mm, achieves an Rthc-a of about 28°C/W.
Different layouts are possible, too. Basic principles, however, suggest to keep the IC and its ground
exposed pad approximately in the middle of the dissipating area; to provide as many vias as possible; to
design a dissipating area having a shape as square as possible and not interrupted by other copper
traces.
Figure 4 : PowerSO-36 SUGGESTED PCB HEATSINK LAYOUT
11/18
11 Page | ||
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| PDF Descargar | [ Datasheet LNBH221.PDF ] | |
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