Final Electrical Specifications
LT1962 Series
300mA, Low Noise,
Micropower
LDO Regulators
April 2000
FEATURES
s
s
s
s
s
s
s
s
s
s
s
DESCRIPTIO
s
s
s
s
Low Noise: 20µV
RMS
(10Hz to 100kHz)
Output Current: 300mA
Low Quiescent Current: 30µA
Wide Input Voltage Range: 1.8V to 20V
Low Dropout Voltage: 270mV
Very Low Shutdown Current: < 1
µ
A
No Protection Diodes Needed
Fixed Output Voltages: 2.5V, 3V, 3.3V, 5V
Adjustable Output from 1.22V to 20V
Stable with 3.3µF Output Capacitor
Stable with Aluminum, Tantalum or
Ceramic
Capacitors
Reverse Battery Protection
No Reverse Current
Overcurrent and Overtemperature Protected
8-Lead MSOP Package
APPLICATIO S
s
s
s
Cellular Phones
Battery-Powered Systems
Noise-Sensitive Instrumentation Systems
The LT
®
1962 series are micropower, low noise, low
dropout regulators. The devices are capable of supplying
300mA of output current with a dropout voltage of 300mV.
Designed for use in battery-powered systems, the low
30µA quiescent current makes them an ideal choice.
Quiescent current is well controlled; it does not rise in
dropout as it does with many other regulators.
A key feature of the LT1962 regulators is low output noise.
With the addition of an external 0.01µF bypass capacitor,
output noise drops to 20µV
RMS
over a 10Hz to 100kHz
bandwidth. The LT1962 regulators are stable with output
capacitors as low as 3.3µF. Small ceramic capacitors can
be used without the series resistance required by other
regulators.
Internal protection circuitry includes reverse battery pro-
tection, current limiting, thermal limiting and reverse
current protection. The parts come in fixed output volt-
ages of 2.5V, 3V, 3.3V and 5V, and as an adjustable device
with a 1.22V reference voltage. The LT1962 regulators are
available in the 8-lead MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
400
3.3V Low Noise Regulator
DROPOUT VOLTAGE (mV)
V
IN
3.7V TO
20V
IN
1µF
OUT
SENSE
LT1962-3.3
SHDN
GND
BYP
1962 TA01
350
3.3V AT 300mA
20µV
RMS
NOISE
10µF
300
250
200
150
100
50
0
0
50
100
150
200
LOAD CURRENT (mA)
250
300
+
0.01µF
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
Dropout Voltage
1962 TA02
U
U
1
LT1962 Series
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
TOP VIEW
OUT
SENSE/ADJ*
BYP
GND
1
2
3
4
8
7
6
5
IN
NC
NC
SHDN
IN Pin Voltage ........................................................
±20V
OUT Pin Voltage ....................................................
±20V
Input to Output Differential Voltage (Note 2) .........
±20V
SENSE Pin Voltage ...............................................
±20V
ADJ Pin Voltage ......................................................
±7V
BYP Pin Voltage....................................................
±0.6V
SHDN Pin Voltage .................................................
±20V
Output Short-Circut Duration .......................... Indefinite
Operating Junction Temperature Range
(Note 3) ............................................ – 40°C to 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
MS8 PACKAGE
8-LEAD PLASTIC MSOP
LT1962EMS8
LT1962EMS8-2.5
LT1962EMS8-3
LT1962EMS8-3.3
LT1962EMS8-5
MS8 PART MARKING
LTML
LTPT
LTPQ
LTPS
LTPR
*PIN 2: SENSE FOR LT1962-2.5/LT1962-3/
LT1962-3.3/LT1962-5. ADJ FOR LT1962
T
JMAX
= 150°C,
θ
JA
= 125°C/ W
SEE THE APPLICATIONS
INFORMATION SECTION
FOR ADDITIONAL
INFORMATION ON
THERMAL RESISTANCE
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C. (Note 3)
PARAMETER
Minimum Operating Voltage
Regulated Output Voltage
(Note 5)
CONDITIONS
I
LOAD
= 300mA
LT1962-2.5 V
IN
= 3V, I
LOAD
= 1mA
3.5V < V
IN
< 20V, 1mA < I
LOAD
< 300mA
LT1962-3
V
IN
= 3.5V, I
LOAD
= 1mA
4V < V
IN
< 20V, 1mA < I
LOAD
< 300mA
q
q
q
q
q
q
q
q
q
q
q
q
MIN
2.475
2.435
2.970
2.925
3.267
3.220
4.950
4.875
1.208
1.190
TYP
1.8
2.500
2.500
3.000
3.000
3.300
3.300
5.000
5.000
1.220
1.220
1
1
1
1
1
5
7
MAX
2.3
2.525
2.565
3.030
3.075
3.333
3.380
5.050
5.125
1.232
1.250
5
5
5
5
5
12
25
15
30
17
33
25
50
6
12
UNITS
V
V
V
V
V
V
V
V
V
V
V
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
LT1962-3.3 V
IN
= 3.8V, I
LOAD
= 1mA
4.3V < V
IN
< 20V, 1mA < I
LOAD
< 300mA
LT1962-5
ADJ Pin Voltage
(Notes 4, 5)
Line Regulation
LT1962
V
IN
= 5.5V, I
LOAD
= 1mA
6V < V
IN
< 20V, 1mA < I
LOAD
< 300mA
V
IN
= 2V, I
LOAD
= 1mA
2.3V < V
IN
< 20V, 1mA < I
LOAD
< 300mA
∆V
IN
= 3V to 20V, I
LOAD
= 1mA
∆V
IN
= 3.5V to 20V, I
LOAD
= 1mA
∆V
IN
= 3.8V to 20V, I
LOAD
= 1mA
∆V
IN
= 5.5V to 20V, I
LOAD
= 1mA
∆V
IN
= 2V to 20V, I
LOAD
= 1mA
V
IN
= 3.5V,
∆I
LOAD
= 1mA to 300mA
V
IN
= 3.5V,
∆I
LOAD
= 1mA to 300mA
V
IN
= 4V,
∆I
LOAD
= 1mA to 300mA
V
IN
= 4V,
∆I
LOAD
= 1mA to 300mA
V
IN
= 4.3V,
∆I
LOAD
= 1mA to 300mA
V
IN
= 4.3V,
∆I
LOAD
= 1mA to 300mA
V
IN
= 6V,
∆I
LOAD
= 1mA to 300mA
V
IN
= 6V,
∆I
LOAD
= 1mA to 300mA
V
IN
= 2.3V,
∆I
LOAD
= 1mA to 300mA
V
IN
= 2.3V,
∆I
LOAD
= 1mA to 300mA
LT1962-2.5
LT1962-3
LT1962-3.3
LT1962-5
LT1962 (Note 4)
LT1962-2.5
LT1962-3
LT1962-3.3
LT1962-5
LT1962 (Note 4)
Load Regulation
q
7
q
12
q
2
q
2
U
W
U
U
W W
W
LT1962 Series
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C. (Note 2)
PARAMETER
Dropout Voltage
V
IN
= V
OUT(NOMINAL)
(Notes 6, 7)
CONDITIONS
I
LOAD
= 10mA
I
LOAD
= 10mA
I
LOAD
= 50mA
I
LOAD
= 50mA
I
LOAD
= 100mA
I
LOAD
= 100mA
I
LOAD
= 300mA
I
LOAD
= 300mA
GND Pin Current
V
IN
= V
OUT(NOMINAL)
(Notes 6, 8)
I
LOAD
= 0mA
I
LOAD
= 1mA
I
LOAD
= 50mA
I
LOAD
= 100mA
I
LOAD
= 300mA
C
OUT
= 10µF, C
BYP
= 0.01µF, I
LOAD
= 300mA, BW = 10Hz to 100kHz
(Notes 4, 9)
V
OUT
= Off to On
V
OUT
= On to Off
V
SHDN
= 0V
V
SHDN
= 20V
V
IN
= 6V, V
SHDN
= 0V
V
IN
– V
OUT
= 1.5V (Avg), V
RIPPLE
= 0.5V
P-P
, f
RIPPLE
= 120Hz,
I
LOAD
= 300mA
V
IN
= 7V, V
OUT
= 0V
V
IN
= V
OUT(NOMINAL)
+ 1V,
∆V
OUT
= – 0.1V
V
IN
= – 20V, V
OUT
= 0V
LT1962-2.5
LT1962-3
LT1962-3.3
LT1962-5
LT1962 (Note 4)
V
OUT
= 2.5V, V
IN
< 2.5V
V
OUT
= 3V, V
IN
< 3V
V
OUT
= 3.3V, V
IN
< 3.3V
V
OUT
= 5V, V
IN
< 5V
V
OUT
= 1.22V, V
IN
< 1.22V
q
q
q
q
q
MIN
TYP
0.10
0.15
MAX
0.15
0.21
0.20
0.28
0.24
0.33
0.33
0.43
75
120
1.6
3
12
100
2
0.5
5
1
UNITS
V
V
V
V
V
V
V
V
µA
µA
mA
mA
mA
µV
RMS
nA
V
V
µA
µA
µA
dB
mA
mA
q
0.18
q
0.27
q
q
q
q
q
q
30
65
1.1
2
8
20
30
0.25
0.8
0.65
0.01
1
0.1
55
65
700
320
Output Voltage Noise
ADJ Pin Bias Current
Shutdown Threshold
SHDN Pin Current
(Note 10)
Quiescent Current in Shutdown
Ripple Rejection
Current Limit
Input Reverse Leakage Current
Reverse Output Current
(Note 11)
1
10
10
10
10
5
20
20
20
20
10
mA
µA
µA
µA
µA
µA
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
Absolute maximum input to output differential voltage can not be
achieved with all combinations of rated IN pin and OUT pin voltages. With
the IN pin at 20V, the OUT pin may not be pulled below 0V. The total
measured voltage from in to out can not exceed
±20V.
Note 3:
The LT1962 regulators are tested and specified under pulse load
conditions such that T
J
≈
T
A
. The LT1962 is 100% tested at T
A
= 25°C.
Performance at – 40°C and 125°C is assured by design, characterization
and correlation with statistical process controls.
Note 4:
The LT1962 (adjustable version) is tested and specified for these
conditions with the ADJ pin connected to the OUT pin.
Note 5:
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 6:
To satisfy requirements for minimum input voltage, the LT1962
(adjustable version) is tested and specified for these conditions with an
external resistor divider (two 250k resistors) for an output voltage of
2.44V. The external resistor divider will add a 5µA DC load on the output.
Note 7:
Dropout voltage is the minimum input to output voltage differential
needed to maintain regulation at a specified output current. In dropout, the
output voltage will be equal to: V
IN
– V
DROPOUT
.
Note 8:
GND pin current is tested with V
IN
= V
OUT(NOMINAL)
and a current
source load. This means the device is tested while operating in its dropout
region. This is the worst-case GND pin current. The GND pin current will
decrease slightly at higher input voltages.
Note 9:
ADJ pin bias current flows into the ADJ pin.
Note 10:
SHDN pin current flows into the SHDN pin. This current is
included in the specification for GND pin current.
Note 11:
Reverse output current is tested with the IN pin grounded and the
OUT pin forced to the rated output voltage. This current flows into the OUT
pin and out the GND pin.
3
LT1962 Series
PI FU CTIO S
OUT (Pin 1):
Output. The output supplies power to the
load. A minimum output capacitor of 3.3µF is required to
prevent oscillations. Larger output capacitors will be
required for applications with large transient loads to limit
peak voltage transients. See the Applications Information
section for more information on output capacitance and
reverse output characteristics.
SENSE (Pin 2):
Sense. For fixed voltage versions of the
LT1962 (LT1962-2.5/LT1962-3/LT1962-3.3/LT1962-5),
the SENSE pin is the input to the error amplifier. Optimum
regulation will be obtained at the point where the SENSE
pin is connected to the OUT pin of the regulator. In critical
applications, small voltage drops are caused by the resis-
tance (R
P
) of PC traces between the regulator and the load.
These may be eliminated by connecting the SENSE pin to
the output at the load as shown in Figure 1 (Kelvin Sense
Connection). Note that the voltage drop across the exter-
nal PC traces will add to the dropout voltage of the
regulator. The SENSE pin bias current is 10µA at the
nominal rated output voltage. The SENSE pin can be pulled
below ground (as in a dual supply system where the
regulator load is returned to a negative supply) and still
allow the device to start and operate.
ADJ (Pin 2):
Adjust. For the adjustable LT1962, this is the
input to the error amplifier. This pin is internally clamped
to
±7V.
It has a bias current of 30nA which flows into the
pin. The ADJ pin voltage is 1.22V referenced to ground and
the output voltage range is 1.22V to 20V.
BYP (Pin 3):
Bypass. The BYP pin is used to bypass the
reference of the LT1962 to achieve low noise performance
from the regulator. The BYP pin is clamped internally to
±0.6V
(one V
BE
). A small capacitor from the output to this
pin will bypass the reference to lower the output voltage
noise. A maximum value of 0.01µF can be used for
8
IN
LT1962
4
U
U
U
reducing output voltage noise to a typical 20µV
RMS
over a
10Hz to 100kHz bandwidth. If not used, this pin must be
left unconnected.
GND (Pin 4):
Ground.
SHDN (Pin 5):
Shutdown. The SHDN pin is used to put the
LT1962 regulators into a low power shutdown state. The
output will be off when the SHDN pin is pulled low. The
SHDN pin can be driven either by 5V logic or open-
collector logic with a pull-up resistor. The pull-up resistor
is required to supply the pull-up current of the open-
collector gate, normally several microamperes, and the
SHDN pin current, typically 1µA. If unused, the SHDN pin
must be connected to V
IN
. The device will not function if
the SHDN pin is not connected.
NC (Pins 6, 7):
No Connect. For best thermal perfor-
mance, these pins are not internally connected. For im-
proved power handling capabilities, these pins can be
connected to the PC board.
IN (Pin 8):
Input. Power is supplied to the device through
the IN pin. A bypass capacitor is required on this pin if the
device is more than six inches away from the main input
filter capacitor. In general, the output impedance of a
battery rises with frequency, so it is advisable to include a
bypass capacitor in battery-powered circuits. A bypass
capacitor in the range of 1µF to 10µF is sufficient. The
LT1962 regulators are designed to withstand reverse
voltages on the IN pin with respect to ground and the OUT
pin. In the case of a reverse input, which can happen if a
battery is plugged in backwards, the device will act as if
there is a diode in series with its input. There will be no
reverse current flow into the regulator and no reverse
voltage will appear at the load. The device will protect both
itself and the load.
1
R
P
OUT
+
V
IN
5
SHDN
SENSE
2
+
LOAD
GND
4
R
P
1962 F01
Figure 1. Kelvin Sense Connection
LT1962 Series
APPLICATIO S I FOR ATIO
The LT1962 series are 300mA low dropout regulators with
micropower quiescent current and shutdown. The devices
are capable of supplying 300mA at a dropout voltage of
300mV. Output voltage noise can be lowered to 20µV
RMS
over a 10Hz to 100kHz bandwidth with the addition of a
0.01µF reference bypass capacitor. Additionally, the refer-
ence bypass capacitor will improve transient response of
the regulator, lowering the settling time for transient load
conditions. The low operating quiescent current (30µA)
drops to less than 1µA in shutdown. In addition to the low
quiescent current, the LT1962 regulators incorporate sev-
eral protection features which make them ideal for use in
battery-powered systems. The devices are protected
against both reverse input and reverse output voltages. In
battery backup applications where the output can be held
up by a backup battery when the input is pulled to ground,
the LT1962-X acts like it has a diode in series with its
output and prevents reverse current flow. Additionally, in
dual supply applications where the regulator load is re-
turned to a negative supply, the output can be pulled below
ground by as much as 20V and still allow the device to start
and operate.
Adjustable Operation
The adjustable version of the LT1962 has an output
voltage range of 1.22V to 20V. The output voltage is set by
the ratio of two external resistors as shown in Figure 2. The
device servos the output to maintain the ADJ pin voltage
at 1.22V referenced to ground. The current in R1 is then
equal to 1.22V/R1 and the current in R2 is the current in R1
plus the ADJ pin bias current. The ADJ pin bias current,
30nA at 25°C, flows through R2 into the ADJ pin. The
IN
V
IN
LT1962
ADJ
GND
R1
1962 F02
OUT
R2
V
OUT
+
R2
V
OUT
=
1.22V
1
+ +
(
I
ADJ
)(
R2
)
R1
V
ADJ
=
1.22V
I
ADJ
=
30nA AT 25
°
C
OUTPUT RANGE = 1.22V TO 20V
Figure 2. Adjustable Operation
U
output voltage can be calculated using the formula in
Figure 2. The value of R1 should be no greater than 250k
to minimize errors in the output voltage caused by the ADJ
pin bias current. Note that in shutdown the output is turned
off and the divider current will be zero.
The adjustable device is tested and specified with the ADJ
pin tied to the OUT pin for an output voltage of 1.22V.
Specifications for output voltages greater than 1.22V will
be proportional to the ratio of the desired output voltage to
1.22V: V
OUT
/1.22V. For example, load regulation for an
output current change of 1mA to 300mA is – 2mV typical
at V
OUT
= 1.22V. At V
OUT
= 12V, load regulation is:
(12V/1.22V)(–2mV) = – 19.7mV
Bypass Capacitance and Low Noise Performance
The LT1962 regulators may be used with the addition of a
bypass capacitor from V
OUT
to the BYP pin to lower output
voltage noise. A good quality low leakage capacitor is
recommended. This capacitor will bypass the reference of
the regulator, providing a low frequency noise pole. The
noise pole provided by this bypass capacitor will lower the
output voltage noise to as low as 20µV
RMS
with the
addition of a 0.01µF bypass capacitor. Using a bypass
capacitor has the added benefit of improving transient
response. With no bypass capacitor and a 10µF output
capacitor, a 10mA to 300mA load step will settle to within
1% of its final value in less than 100µs. With the addition
of a 0.01µF bypass capacitor, the output will settle to
within 1% for a 10mA to 300mA load step in less than
10µs, with total output voltage deviation of less than 2.5%.
However, regulator start-up time is inversely proportional
to the size of the bypass capacitor, slowing to 15ms with
a 0.01µF bypass capacitor and 10µF output capacitor.
Output Capacitance and Transient Response
The LT1962 regulators are designed to be stable with a
wide range of output capacitors. The ESR of the output
capacitor affects stability, most notably with small capaci-
tors. A minimum output capacitor of 3.3µF with an ESR of
3Ω or less is recommended to prevent oscillations. The
LT1962-X is a micropower device and output transient
response will be a function of output capacitance. Larger
values of output capacitance decrease the peak deviations
W
U U
5
京公网安备 11010802033920号
EEWORLD
