GR47/48 Design Guidelines
BA/SEM/MS 03:0015 Rev A
LZT 123 7596
11
GR 47/48 does not have internal capacitance to supply the large current
peaks during GSM transmission. Therefore on burst transmission the
application DC source is responsible for providing the appropriate
current.
Recommendations to the design of power supplies are given in the
following paragraphs.
V1
3.6V
C1
220uF
C
F
100uF
Low ESR
C
BULK
1000uF
Low ESR
R
LINE
100mohm
R
RX
120ohm
30mA Load
R
TX
1.8ohm
2A Load
J1
577usec
1:8 Duty Cycle
'R
LINE
' represents resistance
of circuit between PSU and
GM47/GM48.
L1
33uH
+
+
+
2 Amp
Vcc
Figure 3.2 - Simplified Power Supply Reference Model
3.3.2 General Recommendations
The power supply conditions for the GR47/GR48Vcc connection are as
follows:
Maximum voltage drop during
transmit burst
200mV
Maximum Ripple
TBD : [estimate 50mV]
Table 3.1
Recommended ESR on CBULK : <100m
Ω
Recommended Maximum DC resistance between PSU and GR47 Vcc :
<200m
Ω
Recommended minimum CBULK : 1000
µ
F [see tables below]
The following tables provide a quick indication to recommended
CBULK capacitance to maintain Vcc drop <200mV for different PSU
current delivery and DC resistance between PSU and Module Vcc.
C
BULK
ESR = 50m
Ω
R
LINE
= 50m
Ω
PSU LIMIT
CBULK (min)
Transmit Burst
Vcc Dip (approx)
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