Final Electrical Specifications
LTC1844 Series
150mA, Micropower,
Low Noise, VLDO
Linear Regulator
May 2003
FEATURES
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
Very Low Dropout:
90mV at 150mA
30mV at 50mA (LTC1844-3.3)
Wide Input Voltage Range: 1.6V to 6.5V
Low 35µA Supply Current, Even in Dropout
Low Noise: 30µV
RMS
(10Hz to 100kHz)
±1.75%
Voltage Accuracy Over Temperature,
Voltage and Current Ranges
Fast Transient Response
10nA Supply Current in Shutdown
Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 2.8V, 3.3V
Adjustable Output Voltage: 1.25V to 6V
Output Current Limit
Reverse-Battery and Reverse-Current Protection
No Protection Diodes Needed
Stable with 1µF Output Capacitor
Stable with Ceramic Capacitors
Short-Circuit and Thermal Overload Protection
Low Profile (1mm) SOT-23 Package
The LTC
®
1844 Series are low noise VLDO
TM
(very low
dropout) linear regulators designed for low power/portable
applications. These regulators can operate from input
voltages as low as 1.6V. Typical output noise is only
30µV
RMS
and typical dropout for the LTC1844-3.3 is just
90mV at the maximum load current of 150mA, reducing to
30mV at 50mA.
The internal P-channel MOSFET pass transistor requires
no base current, allowing the device to draw only 35µA
during normal operation, independent of the dropout
voltage and load current. The quiescent current falls to a
negligible 10nA during shutdown.
Other features include high output voltage accuracy,
excellent transient response, stablity with ultralow ESR
ceramic capacitors as small as 1µF, reverse-battery and
reverse-current protection, short-circuit and thermal
overload protection and output current limiting.
The LTC1844 regulators are available in a low profile
(1mm) SOT-23 (ThinSOT
TM
) package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
VLDO and ThinSOT are trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
Bluetooth/802.11 Cards
PDAs and Notebook Computers
Portable Instruments and Battery-Powered Systems
Cellular Phones
TYPICAL APPLICATIO
V
IN
3.3V TO 6.5V
1µF
OFF ON
3
1
LTC1844-3.3 Dropout Voltage vs Load Current
120
100
Fixed Voltage Low Noise, VLDO Linear Regulator
DROPOUT VOLTAGE (mV)
IN
OUT
LTC1844-3.3
BYP
SHDN
GND
2
4
0.1µF
1844 TA01
5
1µF
V
OUT
3.3V
80
60
40
20
0
0
25
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
50
75
100
I
OUT
(mA)
125
150
1844 TA02
U
U
1844ia
1
LTC1844 Series
ABSOLUTE
AXI U
RATI GS
(Note 1)
Output Short-Circut Duration .......................... Indefinite
Operating Junction Temperature Range
(Notes 2, 10) .....................................–40°C to 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
Supply Voltage (IN) ....................................... – 7V to 7V
Input Voltage
SHDN, BYP, ADJ .................................... – 0.3V to 7V
Output Voltage
OUT ........................................................ – 0.3V to 7V
OUT to IN .................................................. – 7V to 7V
PACKAGE/ORDER I FOR ATIO
TOP VIEW
IN 1
GND 2
SHDN 3
4 BYP
5 OUT
IN 1
GND 2
SHDN 3
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
T
JMAX
= 150°C,
θ
JA
= 250°C/ W,
θ
JC
= 90°C/ W
SEE THE APPLICATIONS INFORMATION SECTION
T
JMAX
= 150°C,
θ
JA
= 250°C/ W,
θ
JC
= 90°C/ W
SEE THE APPLICATIONS INFORMATION SECTION
ORDER PART
NUMBER
LTC1844ES5-1.5
LTC1844ES5-1.8
LTC1844ES5-2.5
LTC1844ES5-2.8
LTC1844ES5-3.3
S5 PART
MARKING
LTF1
LTF2
LTF3
LTQK
LTF4
ORDER PART
NUMBER
LTC1844ES5-SD
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
I
IN
I
INSHDN
V
OUT%
PARAMETER
Input Voltage
Quiescent Current
V
IN
Shutdown Supply Current
Regulated Output Voltage
(Notes 3, 4, 5)
SHDN = V
IN
CONDITIONS
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= V
OUT
+ 0.5V, unless otherwise noted. (Note 2)
MIN
q
q
SHDN = 0V
LTC1844-3.3
LTC1844-3.3
LTC1844-2.8
LTC1844-2.8
LTC1844-2.5
LTC1844-2.5
LTC1844-1.8
LTC1844-1.8
V
IN
= 3.8V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 3.8V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 3.3V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 3.3V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 3.0V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 3.0V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 2.3V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 2.3V to 6.5V, I
OUT
= 0mA to 150mA
2
U
U
W
W W
U
W
TOP VIEW
5 OUT
IN 1
GND 2
4 ADJ
BYP 3
TOP VIEW
5 OUT
4 ADJ
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
T
JMAX
= 150°C,
θ
JA
= 250°C/ W,
θ
JC
= 90°C/ W
SEE THE APPLICATIONS INFORMATION SECTION
S5 PART
MARKING
LTE8
ORDER PART
NUMBER
LTC1844ES5-BYP
S5 PART
MARKING
LTE9
TYP
35
MAX
6.5
55
80
1
1.50
1.75
1.50
1.75
1.50
1.75
1.50
1.75
UNITS
V
µA
µA
µA
%V
OUT
%V
OUT
%V
OUT
%V
OUT
%V
OUT
%V
OUT
%V
OUT
%V
OUT
1.6
q
q
q
q
q
0.01
–1.50
–1.75
–1.50
–1.75
–1.50
–1.75
–1.50
–1.75
1844ia
LTC1844 Series
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
LTC1844-1.5
LTC1844-1.5
LTC1844-1.5
LTC1844-BYP
LTC1844-BYP
LTC1844-BYP
LTC1844-SD
LTC1844-SD
LTC1844-SD
∆V
LNR
Line Regulation (Notes 3, 5)
LTC1844-3.3
LTC1844-2.8
LTC1844-2.5
LTC1844-1.8
V
IN
= 2.0V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 2.2V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 2.0V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 1.75V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 2.2V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 1.75V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 1.75V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 2.2V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 1.75V to 6.5V, I
OUT
= 0mA to 150mA
V
IN
= 3.4V to 6.5V, I
L
= 1mA
V
IN
= 2.9V to 6.5V, I
L
= 1mA
V
IN
= 2.6V to 6.5V, I
L
= 1mA
V
IN
= 2.2V to 6.5V, I
L
= 1mA
V
IN
= 1.9V to 6.5V, I
L
= 1mA
V
IN
= 1.9V to 6.5V, I
L
= 1mA
V
IN
= 2.2V to 6.5V, I
L
= 1mA
V
IN
= 1.6V to 6.5V, I
L
= 1mA
V
IN
= 1.6V to 6.5V, I
L
= 1mA
V
IN
= 2.2V to 6.5V, I
L
= 1mA
V
IN
= 1.6V to 6.5V, I
L
= 1mA
V
IN
= 1.6V to 6.5V, I
L
= 1mA
V
IN
= 2.2V to 6.5V, I
L
= 1mA
V
IN
= 1.6V to 6.5V, I
L
= 1mA
V
IN
= 1.6V to 6.5V, I
L
= 1mA
V
IN
= 3.8V, I
OUT
= 0mA to 150mA
V
IN
= 3.3V, I
OUT
= 0mA to 150mA
V
IN
= 3.0V, I
OUT
= 0mA to 150mA
V
IN
= 2.3V, I
OUT
= 0mA to 150mA
V
IN
= 2.2V, I
OUT
= 0mA to 150mA
V
IN
= 2.0V, I
OUT
= 0mA to 150mA
V
IN
= 2.2V, I
OUT
= 0mA to 150mA
V
IN
= 1.75V, I
OUT
= 0mA to 150mA
V
IN
= 2.2V, I
OUT
= 0mA to 150mA
V
IN
= 1.75V, I
OUT
= 0mA to 150mA
I
OUT
= 50mA
I
OUT
= 150mA
I
OUT
= 50mA
I
OUT
= 150mA
I
OUT
= 50mA
I
OUT
= 150mA
I
OUT
= 50mA
I
OUT
= 150mA
I
OUT
= 50mA
I
OUT
= 150mA
I
OUT
= 50mA
I
OUT
= 150mA
I
OUT
= 50mA
I
OUT
= 150mA
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
q
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= V
OUT
+ 0.5V, unless otherwise noted. (Note 2)
MIN
–1.50
–2.00
–2.50
–1.50
–1.75
–3.50
–1.50
–1.75
–3.50
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
9
9
9
9
9
9
9
9
9
9
30
90
35
105
45
135
85
230
115
350
45
135
45
135
TYP
MAX
1.50
2.00
2.00
1.50
1.75
1.75
1.50
1.75
1.75
20
20
20
20
20
30
20
20
80
20
20
80
20
20
80
20
20
20
20
20
40
20
50
20
50
55
150
60
165
75
200
120
300
160
450
75
200
75
200
UNITS
%V
OUT
%V
OUT
%V
OUT
%V
OUT
%V
OUT
%V
OUT
%V
OUT
%V
OUT
%V
OUT
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
1844ia
LTC1844-1.5
LTC1844-BYP
LTC1844-SD
∆V
LDR
Load Regulation (Notes 3, 5)
LTC1844-3.3
LTC1844-2.8
LTC1844-2.5
LTC1844-1.8
LTC1844-1.5
LTC1844-BYP
LTC1844-SD
∆V
DO
Dropout Voltage (Notes 6, 7)
LTC1844-3.3
LTC1844-2.8
LTC1844-2.5
LTC1844-1.8
LTC1844-1.5
LTC1844-BYP
LTC1844-SD
3
LTC1844 Series
ELECTRICAL CHARACTERISTICS
SYMBOL
I
LIM
e
n
V
SHDN
t
DELAY
T
SHDN
∆T
SHDN
I
ADJ
I
IRL
PARAMETER
Output Current Limit
Output Voltage Noise
SHDN Input Threshold
Shutdown Exit Delay
Thermal Shutdown Limit
Thermal Shutdown Hysteresis
ADJ Pin Bias Current
Input Reverse Leakage Current
(Notes 3, 8)
LTC1844-3.3, LTC1844-2.8, LTC1844-2.5, LTC1844-1.8,
LTC1844-1.5, V
IN
= –5V, V
OUT
= 0V
LTC1844-BYP, LTC1844-SD, V
IN
= –5V, V
OUT
= 0V
I
ORL
V
OSH
V
RP
Output Reverse Leakage Current
(Note 9)
Start-Up Overshoot
Output Ripple Rejection
V
IN
= 0V, V
OUT
= V
OUT(NOMINAL)
V
IN
= 0V, V
OUT
= V
OUT(NOMINAL)
R
L
= 1k, SHDN Rise Time
≤
1µs
(V
IN
– V
OUT
) = 1V (Avg), V
RIPPLE
= 0.5V
P-P
,
f
RIPPLE
= 120Hz, I
LOAD
= 100mA
q
q
q
q
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= V
OUT
+ 0.5V, unless otherwise noted. (Note 2)
CONDITIONS
q
MIN
160
TYP
350
35
30
MAX
UNITS
mA
µV
RMS
µV
RMS
f = 10Hz to 100kHz, C
BP
= 0.1µF, C
OUT
= 1µF, I
L
= 150mA
f = 10Hz to 100kHz, C
BP
= 0.1µF, C
OUT
= 10µF, I
L
= 150mA
q
0.35
0.65
70
0.9
100
200
V
µs
µs
°C
°C
C
BP
= 0.01µF, C
OUT
= 1µF, No load
C
BP
= 0.01µF, C
OUT
= 1µF, No load
q
155
10
30
200
1000
0.01
2
60
100
500
1500
0.1
1.2
nA
µA
µA
µA
µA
%V
OUT
dB
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LTC1844 is tested and specified under pulse load conditions
such that T
J
≈
T
A
. The LTC1844E is guaranteed to meet performance
specifications from 0°C to 70°C. Specifications over the – 40°C to 125°C
operating junction temperature range are assured by design,
characterization and correlation with statistical process controls.
Note 3:
The LTC1844 adjustable versions are tested and specifed for these
conditions with the ADJ pin connected to the OUT pin for a V
OUT(NOMINAL)
of 1.252V.
Note 4:
Operating conditions are limited by maximum junction
temperature. The regulated output voltage specification will not apply for
all possible combinations of input voltage and output current. When
operating at maximum input voltage, the output current range must be
limited. When operating at maximum output current, the input voltage
range must be limited.
Note 5:
The LTC1844’s high precision degrades slightly at high
temperatures (T
J
> 70°C) with input voltages below 2.2V. The lower output
voltage versions have been split into higher and lower accuracy input
voltage ranges to reflect this.
Note 6:
To ensure adequate input supply voltage, the LTC1844 adjustable
versions are tested and specified for these conditions with an external
resistor divider (two 100k resistors) for an output voltage of 2.504V. The
external resistor divider will add a 5µA load on the output.
Note 7:
Dropout voltage is (V
IN
– V
OUT
) when V
OUT
falls to 100mV below
its nominal value measured at V
IN
= V
OUT
+ 0.5V. For example, the
LTC1844-3.3 is tested by measuring the V
OUT
at V
IN
= 3.8V, then V
IN
is
lowered until V
OUT
falls 100mV below the measured value. The difference
(V
IN
– V
OUT
) is then measured and defined as
∆V
DO
.
Note 8:
ADJ pin bias current flows into the ADJ pin.
Note 9:
Output reverse leakage current is tested with the IN pin grounded
and the OUT pin forced to the rated output voltage.
Note 10:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
1844ia
4
LTC1844 Series
PI FU CTIO S
IN (Pin 1):
Power for LTC1844 and Load. Power is supplied
to the device through the IN pin. The IN pin should be
locally bypassed to ground if the LTC1844 is more than a
few inches away from another source of bulk capacitance.
In general, the output impedance of a battery rises with
frequency, so it is usually adviseable to include an input
bypass capacitor in battery-powered circuits. A capacitor
in the range of 0.1µF to 1µF is usually sufficient. The
LTC1844 is designed to withstand reverse voltages on the
IN pin with respect to both ground and the output pin. In
the case of a reversed input, which can happen if a battery
is plugged in backwards, the LTC1844 will act as if there
is a large resistor in series with its input with only a small
amount of current flow.
GND (Pin 2):
Ground and Heat Sink. Solder to a ground
plane or large pad to maximize heat dissipation.
SHDN (Pin 3, Fixed and SD Devices):
Shutdown, Active
Low. This pin is used to put the LTC1844 into shutdown.
The SHDN pin current is typically less than 10nA. The
SHDN pin cannot be left floating and must be tied to the
input pin if not used. If reverse-battery protection is
desired, the SHDN pin must be tied to the input pin through
a large value resistor (10k to 1M).
ADJ (Pin 4, Adjustable Devices):
Output Adjust. For the
adjustable versions of the LTC1844, this is the input to the
error amplifier. It has a typical bias current of 30nA flowing
into the pin. The ADJ pin reference voltage is 1.25V
referenced to ground. The output voltage range is 1.25V to
6V and is typically set by connecting ADJ to a resistor
divider from OUT to GND. See Figure 2.
BYP (Pin 4, Fixed/Pin 3, BYP Devices):
Noise Bypass.
The BYP pin is used to augment the internal noise filter to
improve low noise performance. A small low leakage
bypass capacitor from this pin to ground will filter the input
of the error amplifier to lower the output voltage noise.
Any value may be used; larger values will result in lower
output noise, but will increase initial power-up time.
Shutdown exit delay time after a brief shutdown (<10ms)
will not be affected. If not used, this pin must be left
unconnected.
OUT (Pin 5):
Voltage Regulated Output. The OUT pin
supplies power to the load. A minimum output capacitor of
1µF is required to ensure stability. Larger output capacitors
may be required for applications with large transient loads
to limit peak voltage transients. See the Applications
Information section for more information on output
capacitance.
U
U
U
1844ia
5
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