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參數(shù)資料
| 型號(hào)： | PCF5078T |
| 廠商： | NXP SEMICONDUCTORS |
| 元件分類： | 通信及網(wǎng)絡(luò) |
| 英文描述： | Power amplifier controller for GSM and PCN systems |
| 中文描述： | SPECIALTY TELECOM CIRCUIT, PDSO8 |
| 文件頁數(shù)： | 4/20頁 |
| 文件大小： | 90K |
| 代理商： | PCF5078T |
1999 Apr 12
4
Philips Semiconductors
Product specification
Power amplifier controller for GSM and
PCN systems
PCF5078
PINNING
FUNCTIONAL DESCRIPTION
General
The PCF5078 integrates an amplifier for the detected RF
voltage from the sensor, an integrator and an active filter
to build a PA control loop with a small amount of passive
components.
The sensor amplifier is able to amplify signals from a RF
power detector in a range of
20 to +15 dBm. This
complies to the PA output power range of GSM and PCN
systems when a directional coupler with 20 dB attenuation
is used.
The Schottky diode for power detection (sensor) is biased
by an integrated current source of 30
μ
A. Variations of the
forward voltage of the diodes with the temperature have no
influence on the measured signal, because they are
cancelled by sampling around the switched capacitor
operational amplifier OP1 (see Fig.1).
SYMBOL
PIN
DESCRIPTION
VC
VINT
VS1
VS2
V
SS
VDAC
VHOME
V
DD
1
2
3
4
5
6
7
8
PA control output voltage
negative integrator input
sensor signal input 1
sensor signal input 2
ground supply
DAC input voltage
home position input voltage
supply voltage
Fig.2 Pin configuration.
handbook, halfpage
1
2
3
4
8
7
6
5
MGS194
PCF5078
VDD
VDAC
VINT
VHOME
VSS
VS2
VS1
VC
An external Digital-to-Analog Converter (DAC) with10-bit
resolution is necessary to control the loop e.g. the
AUXDAC3 of the baseband interface family PCF5073x.
An integrated active filter smooths the voltage steps of the
DAC and avoids a feedthrough of the DAC harmonics into
the modulation spectra of the PA.
The DAC signal and the sensor signal are added by
operational amplifier OP1. The voltage difference of both
signals is integrated by operational amplifier OP4, which
provides the PA control voltage on pin VC. The integration
is performed by means of an external capacitance C
VINT
connected between pins VINT and VC.
The shape of the rising and falling power burst edges can
be determined by means of the DAC voltage (see Fig.3).
Power-down mode
During the not used time slots in Time Division Multiple
Access (TDMA) systems, the PCF5078 must be turned off
by switching off the supply voltage on pin V
DD
.
Initial conditions and start-up
The PCF5078 has been designed to operate in bursts as
required in TDMA systems. For each time slot to be
transmitted it must be powered-up by switching on the
supply voltage. This allows a proper initialization of
switches S1 to S5.
During start-up switches S1, S2 and S3 are closed and
switches S4 and S5 are opened (see Fig.4).
The forward voltages on the Schottky diodes are sampled
on capacitors C1 and C2, respectively, because switch S1
is closed. Moreover, the control voltage on pin VC is
initially forced to pre-bias level V
prebias
because
switches S2 and S3 are closed and switch S4 is opened.
Switch S1 is opened after a fixed time the supply voltage
has been switched on and then the circuit is ready. This
time is defined on-chip and can be maximum 45
μ
s. Once
switch S1 is open, a ramp signal with a minimum
amplitude of 25 mV applied on pin VDAC determines
opening of switch S3 and closing of switch S4 with a delay
of maximum 3
μ
s with respect to the start of the ramp.
After opening switch S3, the control voltage on pin VC
rises in a fixed amount of time to the home position level
so biasing the PA to the beginning of the active range of its
control curve. Switch S2 remains closed during this typical
time of 2
μ
s. When switch S2 is opened, switch S5 is
closed allowing the transfer of any signal coming from
amplifier OP1.
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相關(guān)代理商/技術(shù)參數(shù) |
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| PCF5078T/F2 | 制造商:NXP Semiconductors 功能描述:IC,POWER CONTROL/MANAGEMENT,CMOS,TSSOP,8PIN,PLASTIC |
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| PCF5079HK | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Dual-band power amplifier controller for GSM, PCN and DCS |
| PCF5079T | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Dual-band power amplifier controller for GSM, PCN and DCS |
| PCF5081 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:GSM baseband processors for digital mobile cellular radio |
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