lnbeh21 STMicroelectronics, lnbeh21 Datasheet - Page 10

• Manufacturer Part Number: lnbeh21
• Description: Lnb Supply And Control Ic With Step-up Converter And Ic Interface
• Manufacturer: STMicroelectronics

LNBEH21
Figure 7: DETIN/DSQOUT Circuit
13/18V Control Word mode, OM=1
When OM=1 the VOM is used to force the DC/DC Converter output voltage (V
control the TEN/VSEL pin function. According to the VOM selection TEN/VSEL will absolve two different
functions:
1)VOM=0 - TEN/VSEL pin controls both the post regulator output voltage (V
Converter output voltage (V
2)VOM=1 - TEN/VSEL pin controls only the post regulator output voltage while the DC/DC Converter
output voltage is forced in a steady state, at the high level, 22.7V typ. with LLC=1 and 21.7V typ. if LLC=0.
During normal operation, when no 13/18V control word is transmitted, the device must work with VOM=0
and TEN/VSEL pin is used to select the odd or even numbered transponder setting up the post regulator
output voltage in a steady state (13.25 or 19.5V); the V
V
Before the beginning of the 13/18V Control Word Communication, it is mandatory to set VOM at HIGH
level forcing the V
command to the TEN/VSEL pin. During the 13/18V pulses, the V
and 19.5V of are fully controlled by the internal voltage reference and they are maintained on a typical
value of 575µs, this time is guaranteed with a maximum output capacitance of 330nF and a load current
in the range of 6 to 450mA. As soon as the communication has expired VOM bit must be set LOW to avoid
any additional power dissipation (See Thermal Design Note). Refer to 13/18V Control Word section in the
complete truth table on page 11 for detailed logic combination and corresponding function description.
10/22
OUT
value in order to minimize the power dissipation.
LNBEH21
Detector
Tone
UP
at 21.7V typ.; after a certain setup time the µP can start to send the 13/18V pulses
DETIN
DSQOUT
R1
2.5K
UP
).
C6
100nF
VDD
(5V)
to DiSEqC bus
PWK data out
(LNB)
0
5V
Figure 8: DETIN/DSQOUT Waveform
CH1=22KHz Tone to DETIN, CH2=PWK data at DSQOUT
UP
voltage is selected by the IC according to the
OUT
rise and fall time between 13.25V
UP
) in a steady state and to
OUT
) and the DC/DC