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PDF ADM666A Data sheet ( Hoja de datos )
| Número de pieza | ADM666A | |
| Descripción | Tri-Mode: +3.3 V/ +5 V/ Adjustable Micropower Linear Voltage Regulators | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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a
Tri-Mode: +3.3 V, +5 V, Adjustable
Micropower Linear Voltage Regulators
ADM663A/ADM666A*
FEATURES
Tri-Mode Operation
3.3 V, 5 V Fixed or +1.3 V to +16 V Adjustable
Low Power CMOS: 9 µA max Quiescent Current
High Current 100 mA Output
Low Dropout Voltage
Upgrade for ADM663/ADM666
“Small” 0.1 µF Output Capacitor (0805 Style)
+2 V to +16.5 V Operating Range
Low Battery Detector ADM666A
No Overshoot on Power-Up
Thermal Shutdown
APPLICATIONS
Handheld Instruments
LCD Display Systems
Pagers
Battery Operated Equipment
GENERAL DESCRIPTION
The ADM663A/ADM666A are precision linear voltage regula-
tors featuring a maximum quiescent current of 9 µA. They can
be used to give a fixed +3.3 V or +5 V output with no additional
external components or can be adjusted from 1.3 V to 16 V
using two external resistors. Fixed or adjustable operation is au-
tomatically selected via the VSET input. The low quiescent cur-
rent makes these devices especially suitable for battery powered
systems. The input voltage range is 2 V to 16.5 V, and an out-
put current up to 100 mA is provided. Current limiting may be
set using a single external resistor. For additional safety, an
internal thermal shutdown circuit monitors the internal die
temperature.
The ADM666A features additional low battery monitoring cir-
cuitry to detect for low battery voltages.
The ADM663A/ADM666A are pin compatible enhancements
for the ADM663/ADM666. Improvements include an addi-
tional 3.3 V output range, higher output current, and operation
with a small output capacitor.
The ADM663A/ADM666A are available in an 8-pin DIP and
narrow surface mount (SOIC) packages.
FUNCTIONAL BLOCK DIAGRAMS
VIN
SHDN
GND
VIN
SHDN
GND
1.3V
A1
VOUT2
VOUT1
0.5V
C1
SEN SE
D
E C2 VIN–50mV
C
O
D
E C3
VSET
R
50mV
R1
R2 0.9V A2
VTC
R3
ADM663A
1.3 V
A1
VOUT
0.5V
C1
SEN SE
D
E C2 VIN–50mV
C
O VSET
D
E C3
R
50mV
R1 LBI
1.3V C4
R2
LBO
R3 ADM666A
*Patent pending.
REV. 0
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
1 page  
The resistor values may be selected by first choosing a value for
R1 and then selecting R2 according to the following equation:
R2
=
R1 ×
V OUT
1.30
− 1
The input leakage current on VSET is 10 nA maximum. This al-
lows large resistor values to be chosen for R1 and R2 with little
degradation in accuracy. For example, a 1 MΩ resistor may be
selected for R1, and then R2 may be calculated accordingly.
The tolerance on VSET is guaranteed at less than ± 30 mV so in
most applications, fixed resistors will be suitable.
+2V TO +16V
INPUT
VIN
ADM663A
ADM666A
SHDN
GND
SENSE
VOUT(2)
RCL
VSET
+1.3V TO +15V
OUTPUT
R2
R1
Figure 5. Adjustable Output
Table I. Output Voltage Selection
VSET
GND
VIN
R1/R2
VOUT
+5 V
+3 V
ADJ
Current Limiting
Current limiting may be achieved by using an external current
sense resistor in series with VOUT(2). When the voltage across
the sense resistor exceeds the internal 0.5 V threshold, current
limiting is activated. The sense resistor is therefore chosen such
that the voltage across it will be 0.5 V when the desired current
limit is reached.
RCL
=
0. 5
ICL
where RCL is the current sense resistor, ICL is the maximum
current limit.
The value chosen for RCL should also ensure that the current is
limited to less than the 100 mA absolute maximum rating and
also that the power dissipation will also be within the package
maximum ratings.
If current limiting is employed, there will be an additional volt-
age drop across the sense resistor that must be considered when
determining the regulators dropout voltage.
If current limiting is not used, the SENSE input should be con-
nected to VOUT(2).
Shutdown Input (SHDN)
The SHDN input allows the regulator to be turned off with a
logic level signal. This will disable the output and reduce
ADM663A/ADM666A
the current drain to a low quiescent (9 µA maximum) current.
This is very useful for low power applications. The SHDN input
should be driven with a CMOS logic level signal since the input
threshold is 0.3 V. In TTL systems, an open collector driver
with a pull-up resistor may be used.
If the shutdown function is not being used, then it should be
connected to GND.
Low Supply or Low Battery Detection
The ADM666A contains on-chip circuitry for low power supply
or battery detection. If the voltage on the LBI pin falls below the
internal 1.3 V reference, then the open drain output LBO will
go low. The low threshold voltage may be set to any voltage
above 1.3 V by appropriate resistor divider selection.
R3
=
R4
V BATT
1.3 V
− 1
where R3 and R4 are the resistive divider resistors and VBATT is
the desired low voltage threshold.
Since the LBI input leakage current is less than 10 nA, large val-
ues may be selected for R3 and R4 in order to minimize loading.
For example, a 6 V low threshold may be set using 10 MΩ for
R3 and 2.7 M Ω for R4.
+2V TO +16V
INPUT
R3
R4
VIN SENSE
ADM666A VOUT
RCL
LBI
SHDN GND
VSET
LBO
LOW
BATTERY
OUTPU T
+1.3V TO +15V
OUTPUT
R2
R1
Figure 6. ADM666A Adjustable Output with Low Battery
Detection
High Current Operation
The ADM663A contains an additional output, VOUT1, suitable
for directly driving the base of an external NPN transistor. Fig-
ure 7 shows a configuration which can be used to provide +5 V
with boosted current drive. A 1 Ω current sensing resistor limits
the current at 0.5 A.
VIN
+
10µ F
SHUTDOWN
VIN VOUT1
ADM663A VOUT2
SHDN
2N 4237
100Ω
1.0Ω
VSET
GND
SENSE
+
10µF
+5V, 0.5A
OUTPUT
Figure 7. ADM663A Boosted Output Current (0.5 A)
REV. 0
–5–
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