GR47/48 Design Guidelines
BA/SEM/MS 03:0015 Rev A
LZT 123 7596
35
A
B
C
D
E
F
G
577
µ
s
TRANSMIT
GM47 Vcc
Figure 2 - Transmit Burst Vcc Waveform
A. The sharp fall in voltage in this region is caused by the ESR
of the capacitors (mounted as close to the module Vcc pins
as possible.
B. The RC discharge is controlled by CBULK, RLINE, and RTX.
C. If the PSU cannot supply the 2A max load of the GR47 and
current limit is reached the discharge of CBULK goes linear.
If current limit is not reached then section ‘B’ will continue for
the length of the transmit burst. Current limit will be reached
when the voltage dropped across RLINE reaches V = ILIM *
RLINE.
D. The sharp fall in voltage in this region is again caused by the
ESR of the capacitors.
E. CBULK will charge linearly while the supply is in current limit.
This section is not relevant while the PSU is not current
limited.
F. The RC charge is controlled by CBULK and RLINE.
G. Once the transmit burst is finished, the 1:8 duty cycle should
ensure that there is sufficient time for the PSU to fully
recover before the next transmit burst.
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