下载
REV. B
AD8315
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 www.analog.com
Fax: 781/326-8703 © 2003 Analog Devices, Inc. All rights reserved.
50 dB GSM PA Controller
FUNCTIONAL BLOCK DIAGRAM
10dB
OFFSET
COMP’N
INTERCEPT
POSITIONING
10dB10dB10dB
DETDETDETDETDET
RFIN
1.35
HI-Z
LOW NOISE (25nV/ Hz)
RAIL-TO-RAIL BUFFER
V-I
VSET
23mV/dB
250mV to
1.4V = 50dB
FLTR
VAPC
OUTPUT
ENABLE
DELAY
LOW NOISE
BAND GAP
REFERENCE
LOW NOISE
GAIN BIAS
COMM
VPOS
ENBL
FEATURES
Complete RF Detector/Controller Function
>50 dB Range at 0.9 GHz (–49 dBm to +2 dBm re 50 )
Accurate Scaling from 0.1 GHz to 2.5 GHz
Temperature-Stable Linear-in-dB Response
Log Slope of 23 mV/dB, Intercept at –60 dBm at 0.9 GHz
True Integration Function in Control Loop
Low Power: 20 mW at 2.7 V, 38 mW at 5 V
Power Down to 10.8 W
APPLICATIONS
Single, Dual, and Triple Band Mobile Handset
(GSM, DCS, EDGE)
Transmitter Power Control
PRODUCT DESCRIPTION
The AD8315 is a complete low cost subsystem for the precise
control of RF power amplifiers operating in the frequency range
0.1 GHz–2.5 GHz and over a typical dynamic range of 50 dB. It is
intended for use in cellular handsets and other battery-operated
wireless devices. The log amp technique provides a much wider
measurement range and better accuracy than controllers using
diode detectors. In particular, its temperature stability is excellent
over a specified range of –30∞C to +85∞C.
Its high sensitivity allows control at low signal levels, thus reduc-
ing the amount of power that needs to be coupled to the detector.
For convenience, the signal is internally ac-coupled. This
high-pass coupling, with a corner at approximately 0.016 GHz,
determines the lowest operating frequency. Thus, the source
may be dc grounded.
The AD8315 provides a voltage output, VAPC, that has the
voltage range and current drive to directly connect to most hand-
set power amplifiers’ gain control pin. VAPC can swing from 250
mV above ground to within 200 mV below the supply voltage.
Load currents of up to 6 mA can be supported.
The setpoint control input is applied to pin VSET and has an
operating range of 0.25 V–1.4 V. The associated circuit deter-
mines the slope and intercept of the linear-in-dB measurement
system; these are nominally 23 mV/dB and –60 dBm for a 50 W
termination (–73 dBV) at 0.9 GHz. Further simplifying the
application of the AD8315, the input resistance of the setpoint
interface is over 100 MW, and the bias current is typically 0.5 mA.
The AD8315 is available in MSOP and lead frame chip scale
(LFCSP) packages and consumes 8.5 mA from a 2.7 V to 5.5 V
supply. When powered down, the sleep current is 4 mA.
