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PDF PCF5078 Data sheet ( Hoja de datos )
| Número de pieza | PCF5078 | |
| Descripción | Power amplifier controller for GSM and PCN systems | |
| Fabricantes | NXP Semiconductors | |
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INTEGRATED CIRCUITS
DATA SHEET
PCF5078
Power amplifier controller for GSM
and PCN systems
Product specification
File under Integrated Circuits, IC17
1999 Apr 12
1 page  
Philips Semiconductors
Power amplifier controller for GSM and
PCN systems
Product specification
PCF5078
After this preset, the control voltage is free to increase
according to the control loop if RF input is present
(see Fig.3).
For higher DAC ramp steps the delay time of opening
switch S3 (and closing switch S4) is reduced. On the
contrary, the delay time between opening switch S2 with
respect to opening switch S3 (and closing switch S4)
remains unchanged.
For a correct start-up it is required that the rising time of the
supply voltage is maximum 20 µs.
End of a burst
For a proper down ramp, the final value of the DAC input
voltage should be below the value at the beginning of the
burst and so be able to really shut-off the PA (see Fig.5).
This means the code programmed for the last bit of the
DAC down ramp (CODEEND) has to be lower than the
initial value of the up ramp (CODESTART). Moreover, the
last code must be maintained until the supply voltage has
been switched off.
When the voltage on pin VC is detected to be lower than
VVHOME a built-in mechanism forces the voltage on pin VC
to Vprebias by closing switches S1, S2 and S3 and by
opening switches S4 and S5.
For proper operation, the supply voltage should be
switched off at least 15 µs later with respect to the end of
the down ramp on pin VDAC.
PA protection against mismatching
A second sensor amplified input is integrated into the
PCF5078 for measuring the reflected wave of the
directional coupler. The signal is added to the measured
RF power signal (see Fig.3). When mismatching at the
output of the PA occurs the power is reduced. A high
Voltage Standing Wave Ratio (VSWR) at the output of the
PA often occurs in systems where the PA is connected to
the antenna via switches with low attenuation instead of
using a duplex filter.
Home position voltage
A forward voltage of an on-chip silicon diode is provided as
the default home position voltage Vhome. This voltage
matches the requirements at the control input of most PAs
and exhibits the same temperature coefficient.
However, if another value is needed for a certain PA the
level can be adjusted by connecting external components
to pin VHOME (see Figs 10 and 11). The home position
voltage can be set between 200 and 1000 mV when using
a capacitor of 50 pF connected between pins VINT
and VC.
1999 Apr 12
5
5 Page 
Philips Semiconductors
Power amplifier controller for GSM and
PCN systems
Product specification
PCF5078
handbook1, .h0alfpage
TC
(mV/K)
0.8
MGS199
0.6
0.4
0.2
2 3 4 VDD (V) 5
Fig.8 Temperature coefficient of the minimum
output voltage as a function of the supply
voltage.
APPLICATION INFORMATION
handbook, full pagewidathntenna
sensor
PA RF
D1 D2
VC 1
8 VDD
R2
1 kΩ
R1
1 kΩ
C1 VINT 2
C2 2.2 to 10 nF
7 VHOME
<50 pF
PCF5078
C3 22 to 82 pF
VS1 3
6 VDAC
0.2 to 2.5 V
VS2
4
5 VSS
AUXDAC3
PCF5073x
MGS201
Fig.9 Application diagram for mobile station with PA protection against mismatching.
1999 Apr 12
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet PCF5078.PDF ] | |
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