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PDF DR280 Data sheet ( Hoja de datos )
| Número de pieza | DR280 | |
| Descripción | 1.2 V Ultralow Power High PSRR Voltage Reference | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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FEATURES
1.2 V Precision Output
Excellent Line Regulation, 2 ppm/V Typical
High Power Supply Ripple Rejection, –80 dB at 220 Hz
Ultralow Power, Supply Current 16 A Maximum
Temperature Coefficient, 40 ppm/oC Maximum
Low Noise, 12.5 nV/÷Hz Typical
Operating Supply Range, 2.4 V to 5.5 V
Compact 3-Lead SOT-23 and SC70 Packages
APPLICATIONS
GSM, GPRS, 3G Mobile Stations
Portable Battery-Operated Electronics
Low Voltage Converter References
Wireless Devices
GENERAL DESCRIPTION
The ADR280 is a 1.2 V band gap core reference with excellent
line regulation and power supply rejection designed specifically
for applications experiencing heavy dynamic supply variations,
such as data converter references in GSM, GPRS, and 3G
mobile station applications. Devices such as the AD6535, which
has an analog baseband IC with on-board baseband and audio
codecs, voltage regulators, and battery charger, rely on the
ADR280’s ability to reject input battery voltage variations during
RF power amplifier activity.
In addition to mobile stations, the ADR280 is suitable for a
variety of general-purpose applications. Most band gap refer-
ences include internal gain for specific outputs, which simplifies
the user’s design but compromises on the cost, form factor, and
flexibility. The ADR280, on the other hand, optimizes the band
gap core voltage and allows users to tailor the voltage, current, or
transient response by simply adding their preferred op amps.
The ADR280 operates on a wide supply voltage range from 2.4V
to 5.5 V. It is available in compact 3-lead SOT-23 and SC70
packages. The device is specified over the extended industrial
temperature range of –40°C to +85°C.
1.2 V Ultralow Power
High PSRR Voltage Reference
ADR280
PIN CONFIGURATIONS
3-Lead SOT-23
(RT Suffix)
V+ 1
ADR280 3 V–
VOUT 2
3-Lead SC70
(KS Suffix)
VOUT 1
ADR280 3 V–
V+ 2
15
10
5
3V TO 5V
0
–5
–10
–15
–40
–20
0
20 40
60
TEMPERATURE (C)
80 100
Figure 1. Line Regulation vs.Temperature
REV. A
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 oth-
erwise 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.
1 page  
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ADR280
The ADR280 provides the core 1.2 V band gap voltage and is
able to drive a maximum load of only 100 µA. Users can simply
buffer the output for high current or sink/source current applica-
tions, such as ADC or LCD driver references (see Figure 5).
0.1F
U1
V+
ADR280
V–
VOUT
U2
VOUT
0.1F
U2 = AD8541, SC70
AD8601, SOT-23-5
Figure 5. Buffered Output
Users can also tailor any specific need for voltage and dynamics
with an external op amp and discrete components (see Figure 5).
Depending on the specific op amp and PCB layout, it may be
necessary to add a compensation capacitor, C2, to prevent gain
peaking and oscillation. The exact value of C2 needed requires
some trial and error but usually falls in the range of a few pF.
U1
5V V+
ADR280
5V V–
VO
1.8V
R2
60k 0.1%
U2 V+
AD8541
V–
C2 2.2pF
1.2V
VOUT
C1 0.1F
R1
120k 0.1%
Figure 6. 1.8 V Reference
LOW COST, LOW POWER CURRENT SOURCE
Because of its low power characteristics, the ADR280 can be
converted to a current source with just a setting resistor. In addi-
tion to the ADR280 current capability, the supply voltage and the
load limit the maximum current. The circuit in Figure 7 produces
100 µA with 2 V compliance at 5 V supply. The load current is
the sum of ISET and IGND. IGND will increase slightly with load; an
RSET of 13.6 k yields 100 µA of load current.
U1
5V V+
ADR280
V–
ISET
+
RSET
1.2V
–
C1
13.6k
VOUT
0.1F
RL 1k IL
100A
IGND
IL = ISET + IGND
Precision Low Power Current Source
By adding a buffer to redirect the IGND in Figure 8, a current can
be precisely set by RSET with the equation IL = 1.2 V/RSET.
U1
5V V+
ADR280
V–
VOUT
C2 0.1F
RSET 12k
5V
V+ U2
AD8541
V–
RL 1k 1IL00A
IL = 1.2V/RSET
Figure 8. Precision Low Power Current Source
Boosted Current Source
Adding one more buffer to the previous circuit boosts the current
to the level that is limited only by the buffer U2 current handling
capability (see Figure 9).
RSET
230
RL
500
U1
5V V+
ADR280
V–
5V
U2
V+
VOUT
V–
C1 0.1F
+
1.2V
–
IL
5mA
5V
V+ U3
V–
IL = 1.2V/RSET
U2 = U3 = AD8542, AD822
Figure 9. Precision Current Source
Figure 7. Low Cost Current Source
REV. A
–5–
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet DR280.PDF ] | |
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