8283
LNB SUPPLY AND
CONTROL-VOLTAGE REGULATOR
ELECTRICAL CHARACTERISTICS at TA = 25°C, ENT = L, EN = H, OSEL = H, LLC = L, VIN = 24 V,
VO = 13 V or 18 V, IO = 50 mA, REXTM = open (unless otherwise noted).
Limits
Characteristic
Symbol Test Conditions
Min.
Typ. Max. Units
Overload Flag Logic Low
Overload Flag Leakage Current
Logic Input Voltage
VOL
IOZ
VIL
VIH
IIL
IOL = 8 mA
0.28
<1.0
0.8
10
V
µA
V
VOH = 5.5 V
0.8
2.0
V
Logic Input Current
Supply Current
VIL = 0 V
<-1.0
<1.0
0.5
-10
10
µA
µA
mA
mA
°C
V
IIH
VIH = 5 V
IIN
Outputs disabled (EN = L)
ENT = H, IO = 600 mA, VO = 13 V
382
165
0.8
Thermal Shutdown Temp.
Linear Regulator Voltage Drop
Switching Frequency
TJ
∆VBUCK VBULK — V
O
fO
16 x ftone
320
400
352
900
0.15
384
kHz
mA
V
Bypass Switch Current Limit
IswM
Vsw
OSEL = L
Bypass Switch Voltage Drop
(MI to LNB)
OSEL = L, Isw = 300 mA
FUNCTIONAL DESCRIPTION
The ENT (Tone Enable) terminal activates the internal
tone signal, modulating the dc output with a ±0.3 V,
22 kHz symmetrical waveform. The internal oscillator is
factory-trimmed to provide a tone of 22 kHz ±2 kHz. No
further adjustment is required. The internal oscillator
operates the buck converter at 16 times the tone fre-
quency.
To improve design flexibility and to allow implemen-
tation of proposed LNB remote control standards, an
analog modulation input terminal is available (EXTM).
An appropriate dc-blocking capacitor must be used to
couple the modulating signal source to the EXTM termi-
nal. If external modulation is not used, the EXTM termi-
nal can be left open.
Burst coding of the 22 kHz tone can be accomplished
due to the fast response of the ENT input and rapid tone
response. This allows implementation of the DiSEqC™
protocols.
Applications that are required to deliver more than
400 mA and use the external modulation terminal should
be rebiased to increase the voltage drop across the linear
regulator. This will allow full modulation under all
conditions.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
4
SANKEN [ SANKEN ELECTRIC ]
