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Product Technical Specification & Customer Design Guidelines
26
Proprietary and Confidential - Specifications subject to change
2400058
3.1.1 Burst transmission current requirements
The power supply must be able to deliver high current peaks in a short time due
to the burst transmission nature of GSM. During these peaks, the ripple (U
ripp
) on
the supply voltage must not exceed the level noted in
describes radio burst rates in connected mode. For detailed power
consumption figures, see
3.1.2 Power input (VCC_3V6)
An external power supply uses the VCC_3V6 pins to:
•
Supply the AirPrime SL808X Embedded Module.
•
Directly supply the RF components with 3.6 V.
·
It is essential to keep a minimum voltage ripple at this connection in order
to avoid any phase error or spectrum modulation degradation.
·
Insufficient power supply can significantly affect RF performance (TX
power, modulation spectrum, EMC performance, spurious emission,
frequency error, etc.).
•
Provide reference voltage VREF_1V8 (through several internal regulators) for
the baseband signals. The host should draw less than 1 mA on this rail.
When the AirPrime SL808X Embedded Module is supplied with a battery, the total
impedance (b prote PCB) should be such that the supply will be
>= 3.3 V during GSM burst mode operation (drawing a maximum peak current of
2.2 A for 577 µs (one slot) or 1154 µs (two slots) TX.
3.1.3 Start-up current
During the first second following Power ON, a current peak occurs. This current
peak (t
Startup
) has a duration of about 165 ms (typical).
indicates the expected peak current range.
Table 3-3: Radio burst rates — Connected mode
GSM / GPRS
Multislot class
a
a. (TBD) Table contents to be updated to classes supported by SL808X.
RF Power
Amplifier
current
Burst duration
Period
Rising
time
Class 10
2.0 A peak
577
µs
4.615 ms
10
µs
Class 12
1154
µs
4.615 ms
Table 3-4: Start-up current peak range
Current peak at
ambient
temperature (25
°
C)
VCC_3V6
min
(3.3 V)
VCC_3V6
typ
(3.6 V)
VCC_3V6
max
(4.3 V)
t
Startup
150 mA
140 mA
115 mA
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