8205
PRELIMINARY INFORMATION
(subject to change without notice)
December 6, 1999
NC
OR
ADJ*
OUT
LOW-DROPOUT REGULATORS
— HIGH EFFICIENCY
Designed specifically to meet the requirement for extended opera-
tion of battery-powered equipment such as cordless and cellular tele-
phones, the A8205SLH voltage regulators offer the reduced dropout
voltage and quiescent current essential for maximum battery life.
Applicable also to palmtop computers and personal data assistants,
these devices deliver a regulated output at up to 200 mA (transient),
which is limited only by package power dissipation. Regulated output
voltages of 2.7, 2.8, 3.0, 3.3, 3.6, 4.0, and 5.0 V are currently provided.
Other voltages, down to 2.0 volts, are available on special order.
A PMOS pass element provides a typical dropout voltage of only
75 mV at 100 mA of load current. The low dropout voltage permits
deeper battery discharge before output regulation is lost. Quiescent
current does not increase significantly as the dropout voltage is ap-
proached, an ideal feature in standby/resume power systems where data
integrity is crucial. Regulator accuracy and excellent temperature
characteristics are provided by a bandgap reference. The A8205SLH
includes an ENABLE input to give the designer complete control over
power up, standby, or power down.
These devices are supplied in a thermally enhanced 5-lead small-
outline plastic package similar to the SOT-23, and fitting the SC-74A
footprint. All devices are rated for operation over a temperature range
of -20°C to +85°C.
Data Sheet
27468.20
5
4
*NO CONNECTION (fixed regulators) or
ADJUST (A8205SLH-ADJ only).
ABSOLUTE MAXIMUM RATINGS
Input Voltage, V
I
. . . . . . . . . . . . . . .
7 V
Peak Output Current,
I
OM
. . . . . . . . . . . . . . . . . .
200 mA*
Enable Input Voltage, V
E
. . . . . . . . . .
V
I
Operating Temperature Range,
T
A
. . . . . . . . . . . . .
-20
°
C to +85
°
C
Junction Temperature, T
J
. . . .
+150
°
C
Storage Temperature Range,
T
S
. . . . . . . . . . . .
-40
°
C to +150
°
C
* Output current rating is limited by input
voltage, duty cycle, and ambient temperature.
Under any set of conditions, do not exceed a
junction temperature of +150°C. See follow-
ing pages.
T
C
U Y
D L
O N
R O
P E
D C
E N
U E
IN ER
T F
N E
O R
C R
IS O
D F
—
VR
1
2
3
Dwg. PS-021-5
ENABLE
GND
IN
FEATURES AND BENEFITS
I
High Efficiency Provides Extended Battery Life
I
75 mV Typical Dropout Voltage at I
O
= 100 mA
I
55
µA
Typical Quiescent Current
Less Than 1
µA
“Sleep” Current
I
Low Output Noise
I
200 mA Peak Output Current
I
Improved PSRR and Transient Performance
APPLICATIONS
I
I
I
I
Cordless and Cellular Telephones
Personal Data Assistants
Personal Communicators
Palmtop Computers
Always order by complete part number, e.g.,
A8205SLH-xx
, where “xx”
is the required output voltage in tenths or “ADJ” for adjustable.
8205
LOW-DROPOUT
REGULATORS
FUNCTIONAL BLOCK DIAGRAM
IN
1
5
OUT
ADJUST
4
BIAS
DRIVE
ERROR
AMP
(SUFFIX "-ADJ" ONLY)
OTHERWISE
NO CONNECTION
(FIXED REG'S)
ENABLE
3
ENABLE
BANDGAP
REF.
2
GND
Dwg. FS-012-6
A8205SLH Maximum Allowable Average Output Current*
with device mounted on 2.24" x 2.24"
(56.9 mm x 56.9 mm) solder-coated copper-clad board in still air.
Allowable Total Average (10 ms) Output Current in Milliamperes with T
J
= 150°C, Duty Cycle = 100%†
V
I
- V
O
T
A
25°C
50°C
70°C
85°C
0.5
200
200
200
200
1.0
200
200
200
200
1.5
200
200
200
197
2.0
200
200
182
148
2.5
200
182
145
118
3.0
189
152
121
98
3.5
162
130
104
84
4.0*
142
114
91
74
4.5*
126
101
81
66
* Absolute maximum peak output current rating is 200 mA; absolute maximum input voltage is 7 V.
† I
O
= (T
J
– T
A
)/([V
I
– V
O
] R
θJA
x dc) = (150 – T
A
)/([V
I
– V
O
] x 220 x 1.00)
Output current rating can be increased (to 200 mA maximum) by additional heat sinking or reducing the duty cycle.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1999, 2000 Allegro MicroSystems, Inc.
8205
LOW-DROPOUT
REGULATORS
APPLICATIONS INFORMATION
Linear regulators require input and output capacitors in order to
maintain over-all loop stability. The recommended minimum
value for the input capacitor is 0.1
µF.
The output capacitor is
the dominant pole that provides the high-frequency compensa-
tion required for over-all regulator loop stability. These devices
are stable with as little as 1
µF.
However, to ensure stable
operation under all conditions and capacitor types, the recom-
mended minimum value is 4.7
µF.
The output capacitor may be
partially distributed through the load circuits. However, at least
1
µF
should be connected at the regulator using the shortest and
widest foil pattern possible.
The A8205SLH-ADJ requires an external voltage divider to set
up the desired regulated output voltage between 2.0 V and 6.8 V
(V
I
≤
7 V). The two resistors are chosen such that
V
O
= 1.26 (R
1
+ R
2
)/R
2
.
The resistor values are usually as high as possible to maintain
high circuit efficiency, but R
2
should be less than 300 kΩ.
INPUT
(7.0 V MAX)
0.1
µF
(MIN)
ENABLE
(ACTIVE HIGH)
OUTPUT (2.0 V TO 6.8 V)
5
1
VR
2
4
3
1
µF
(MIN)
R1
R2
(300 kΩ MAX)
Dwg. ES-015
Thermal Considerations
These devices are intended to provide more than 150 mA of
continuous current in a very small package. The table on page 2
of this data sheet gives the maximum allowable average output
current for a worst-case printed circuit design (R
θJA
= 220°C/W
with a minimum footprint). Performance improvement is easily
accomplished with the addition of 1 square inch of copper at
terminal 2 (R
θJA
= 170°C/W).
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
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