Datasheet
MC33411A/B
34
MOTOROLA RF/IF DEVICE DATA
These values are compared to the internal reference VB
(≈1.5 V) which is available at Pin 37. The value read back
from the LBD A/D will therefor be approximately:
N(for LBD)
[
63 (V
CC
)
2.5(VB)(1.07)
(27)
and for the RSSI
N(for RSSI)
[
63 (RSSIVoltage)
(VB)(1.07)
(28)
VB Voltage Adjust and Characteristics
VB has a production tolerance of ±8%, and can be
adjusted over a ±9% range using bits 3/20–17. The
adjustment steps will be ≈1.2% each (See Table 8). If
desired, VB can be used to bias external circuitry, as long as
the load current on this pin does not exceed 10 µA. V
B
varies
by less than ±0.5% over supply voltage, referenced to V
CC
=
3.6 V.
The value of the de–coupling capacitor connected from VB
to ground affects both the noise and crosstalk from the
receive and transmit audio paths, so the value should be
chosen with caution. Figures 50 and 51 show this
relationship.
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Á
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Á
Table 8. VB Voltage Reference Programming
V
ref
Adjust Bit #20
V
ref
Adjust Bit #19
V
ref
Adjust Bit #18
V
ref
Adjust Bit #17
V
ref
Adjust #
Voltage Reference
Adjustment Amount
0 0 0 0 0 –9.0%
0 0 0 1 1 –7.8%
0 0 1 0 2 –6.6%
0 0 1 1 3 –5.4%
0 1 0 0 4 –4.2%
0 1 0 1 5 –3.0%
0 1 1 0 6 –1.8%
0 1 1 1 7 –0.6%
1 0 0 0 8 0.6%
1 0 0 1 9 1.8%
1 0 1 0 10 3.0%
1 0 1 1 11 4.2%
1 1 0 0 12 5.4%
1 1 0 1 13 6.6%
1 1 1 0 14 7.8%
1 1 1 1 15 9.0%
0.01
–125
–105
0.01
CROSSTALK (dB)
VB CAPACITOR (µF)
–110
–115
–120
0.1 1.0 10
–50
VB CAPACITOR (µF)
Noise
Figure 50. Crosstalk/Noise from
C In to E Out versus VB Capacitor
Figure 51. Crosstalk/Noise from
E In to Tx Out versus VB Capacitor
–107
–87
–92
–97
–102
NOISE LEVEL @ E OUT (dBV)
Crosstalk, 130 Ω load
Crosstalk, no load
0.1 1.0 10
CROSSTALK (dB)
–55
–60
–65
–70
–75
–80
–85
–90
–95
–75
–63
–67
–71
–73
–69
–65
–61
NOISE LEVEL @ Tx OUT (dBV)
Noise
Crosstalk
V
CC
= 3.6 V
T
A
= 25°C
V
CC
= 3.6 V
T
A
= 25°C
ARCHIVE INFORMATION
ARCHIVE INFORMATION
Fr
eescale S
emiconduct
or
, I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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