LT1962EMS8_技术文档

Final Electrical Specifications

LT1962 Series

300mA, Low Noise,

Micropower

LDO Regulators

April 2000

U

FEATURES

DESCRIPTIO

The LT^®1962 series are micropower, low noise, low

dropout regulators. The devices are capable of supplying

300mAofoutputcurrentwithadropoutvoltageof300mV.

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.

■

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: < 1µA

■

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

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_RMSover 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.

■

Reverse Battery Protection

No Reverse Current

Overcurrent and Overtemperature Protected

8-Lead MSOP Package

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.

U

APPLICATIO S

■

Cellular Phones

■

Battery-Powered Systems

■

Noise-Sensitive Instrumentation Systems

, LTC and LT are registered trademarks of Linear Technology Corporation.

U

TYPICAL APPLICATIO

Dropout Voltage

400

3.3V Low Noise Regulator

350

300

250

200

150

100

50

3.3V AT 300mA

20µV NOISE

IN

OUT

V

IN

RMS

+

3.7V TO

20V

1µF

SENSE

10µF

LT1962-3.3

0.01µF

SHDN

GND

BYP

1962 TA01

0

50

100

150

200

250

300

LOAD CURRENT (mA)

1962 TA02

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-

tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.

1

LT1962 Series

W W

U W

U

ABSOLUTE AXI U RATI GS

PACKAGE/ORDER I FOR ATIO

(Note 1)

ORDER PART

NUMBER

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

TOP VIEW

LT1962EMS8

LT1962EMS8-2.5

LT1962EMS8-3

LT1962EMS8-3.3

LT1962EMS8-5

OUT

SENSE/ADJ*

BYP

1

2

3

4

8 IN

7 NC

6 NC

5 SHDN

GND

MS8 PACKAGE

8-LEAD PLASTIC MSOP

*PIN 2: SENSE FOR LT1962-2.5/LT1962-3/

LT1962-3.3/LT1962-5. ADJ FOR LT1962

MS8 PART MARKING

T_JMAX= 150°C, θ_JA= 125°C/ W

LTML

LTPT

LTPQ

LTPS

LTPR

(Note 3) ............................................ –40°C to 125°C

Storage Temperature Range ................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec).................. 300°C

SEE THE APPLICATIONS

INFORMATION SECTION

FOR ADDITIONAL

INFORMATION ON

THERMAL RESISTANCE

Consult factory for Industrial and Military grade parts.

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are T_A= 25°C. (Note 3)

PARAMETER

CONDITIONS

= 300mA

MIN

TYP

MAX

UNITS

Minimum Operating Voltage

I

●

1.8

2.3

V

LOAD

Regulated Output Voltage

(Note 5)

LT1962-2.5

LT1962-3

LT1962-3.3

LT1962-5

LT1962

V

= 3V, I

= 1mA

LOAD

2.475

2.435

2.500

2.525

2.565

V

IN

3.5V < V < 20V, 1mA < I

< 300mA

LOAD

IN

V

= 3.5V, I

IN

= 1mA

LOAD

2.970

2.925

3.000

3.030

3.075

V

IN

4V < V < 20V, 1mA < I

< 300mA

LOAD

V

= 3.8V, I

= 1mA

LOAD

3.267

3.220

3.300

3.333

3.380

V

IN

4.3V < V < 20V, 1mA < I

< 300mA

LOAD

IN

V

= 5.5V, I

IN

= 1mA

LOAD

4.950

4.875

5.000

5.050

5.125

V

IN

6V < V < 20V, 1mA < I

< 300mA

LOAD

ADJ Pin Voltage

(Notes 4, 5)

V

= 2V, I

= 1mA

LOAD

1.208

1.190

1.220

1.232

1.250

V

IN

2.3V < V < 20V, 1mA < I

< 300mA

LOAD

IN

Line Regulation

LT1962-2.5

LT1962-3

LT1962-3.3

LT1962-5

∆V = 3V to 20V, I

= 1mA

●

1

5

mV

IN

LOAD

∆V = 3.5V to 20V, I

= 1mA

IN

LOAD

∆V = 3.8V to 20V, I

IN

∆V = 5.5V to 20V, I

IN

LT1962 (Note 4) ∆V = 2V to 20V, I

= 1mA

IN

LOAD

Load Regulation

LT1962-2.5

V

= 3.5V, ∆I

= 1mA to 300mA

5

12

25

mV

IN

LOAD

●

LT1962-3

V

= 4V, ∆I

= 1mA to 300mA

7

15

30

mV

IN

LOAD

LT1962-3.3

LT1962-5

V

= 4.3V, ∆I

= 1mA to 300mA

7

17

33

mV

IN

LOAD

V

= 6V, ∆I

= 1mA to 300mA

12

2

25

50

mV

IN

LOAD

LT1962 (Note 4)

V

= 2.3V, ∆I

= 1mA to 300mA

6

12

mV

IN

LOAD

2

LT1962 Series

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are T_A= 25°C. (Note 2)

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Dropout Voltage

I

= 10mA

0.10

0.15

0.21

V

LOAD

V

= V

●

IN

OUT(NOMINAL)

(Notes 6, 7)

I

= 50mA

0.15

0.18

0.27

0.20

0.28

V

LOAD

I

= 100mA

0.24

0.33

V

LOAD

I

= 300mA

0.33

0.43

V

LOAD

GND Pin Current

I

= 0mA

= 1mA

= 50mA

= 100mA

= 300mA

●

30

65

1.1

2

75

120

1.6

3

µA

mA

LOAD

V

= V

IN

OUT(NOMINAL)

(Notes 6, 8)

8

12

Output Voltage Noise

ADJ Pin Bias Current

Shutdown Threshold

C

= 10µF, C

= 0.01µF, I

= 300mA, BW = 10Hz to 100kHz

20

30

µV

RMS

OUT

BYP

LOAD

(Notes 4, 9)

100

2

nA

V

= Off to On

= On to Off

●

0.8

0.65

V

OUT

0.25

SHDN Pin Current

(Note 10)

V

= 0V

= 20V

0.01

1

0.5

5

µA

SHDN

Quiescent Current in Shutdown

Ripple Rejection

V

= 6V, V

= 0V

SHDN

0.1

65

1

µA

IN

– V

= 1.5V (Avg), V

= 0.5V , f = 120Hz,

P-P RIPPLE

55

dB

IN

OUT

RIPPLE

I

= 300mA

LOAD

Current Limit

V

= 7V, V

= V

= 0V

700

mA

IN

OUT

OUT(NOMINAL)

+ 1V, ∆V

= –0.1V

●

320

OUT

Input Reverse Leakage Current

V

= –20V, V

= 0V

OUT

1

mA

IN

Reverse Output Current

(Note 11)

LT1962-2.5

LT1962-3

LT1962-3.3

LT1962-5

V

= 2.5V, V < 2.5V

10

5

20

10

µA

OUT

IN

= 3V, V < 3V

IN

= 3.3V, V < 3.3V

IN

= 5V, V < 5V

IN

LT1962 (Note 4)

= 1.22V, V < 1.22V

IN

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

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.

output voltage will be equal to: V – V

.

IN

DROPOUT

Note 3: The LT1962 regulators are tested and specified under pulse load

conditions such that T ≈ T . The LT1962 is 100% tested at T = 25°C.

Note 8: GND pin current is tested with V = V

and a current

IN

OUT(NOMINAL)

J

A

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.

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 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.

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.

3

LT1962 Series

U

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.

reducing output voltage noise to a typical 20µV_RMSover 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.

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)ofPCtracesbetweentheregulatorandtheload.

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

nominalratedoutputvoltage.TheSENSEpincanbepulled

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.

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.

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.TheADJpinvoltageis1.22Vreferencedtogroundand

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

R

P

8

1

2

IN

OUT

LT1962

5

+

SHDN SENSE

LOAD

V

IN

GND

4

R

P

1962 F01

Figure 1. Kelvin Sense Connection

4

LT1962 Series

W U U

APPLICATIO S I FOR ATIO

U

TheLT1962seriesare300mAlowdropoutregulatorswith

micropowerquiescentcurrentandshutdown.Thedevices

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

0.01µFreferencebypasscapacitor. Additionally, therefer-

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

quiescentcurrent, theLT1962regulatorsincorporatesev-

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-

turnedtoanegativesupply,theoutputcanbepulledbelow

groundbyasmuchas20Vandstillallowthedevicetostart

and operate.

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

pinbiascurrent.Notethatinshutdowntheoutputisturned

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_OUTto 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_RMSwith 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,withtotaloutputvoltagedeviationoflessthan2.5%.

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.

Adjustable Operation

The adjustable version of the LT1962 has an output

voltage range of 1.22V to 20V. The output voltage is set by

theratiooftwoexternalresistorsasshowninFigure2.The

device servos the output to maintain the ADJ pin voltage

at 1.22V referenced to ground. The current in R1 is then

equalto1.22V/R1andthecurrentinR2isthecurrentinR1

plus the ADJ pin bias current. The ADJ pin bias current,

30nA at 25°C, flows through R2 into the ADJ pin. The

IN

OUT

ADJ

V

OUT

+

V

LT1962

GND

R2

R1

IN

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

1962 F02

R2

R1

V_OUT= 1.22V 1+

_ADJ= 1.22V

_ADJ= 30nA AT 25°C

OUTPUT RANGE = 1.22V TO 20V

+ I

R2

(

_ADJ)(

)

V

I

Figure 2. Adjustable Operation

5

LT1962 Series

W U U

U

APPLICATIO S I FOR ATIO

40

and provide improved transient response for larger load

current changes. Bypass capacitors, used to decouple

individual components powered by the LT1962, will in-

crease the effective output capacitor value. With larger

capacitors used to bypass the reference (for low noise

operation),largervaluesofoutputcapacitanceareneeded.

For 100pF of bypass capacitance, 4.7µF of output capaci-

tor is recommended. With a 1000pF bypass capacitor or

larger, a 6.8µF output capacitor is recommended.

20

0

X5R

–20

–40

–60

–80

–100

Y5V

BOTH CAPACITORS ARE 16V,

1210 CASE SIZE, 10µF

Extra consideration must be given to the use of ceramic

capacitors. Ceramic capacitors are manufactured with a

variety of dielectrics, each with different behavior across

temperature and applied voltage. The most common

dielectrics used are Z5U, Y5V, X5R and X7R. The Z5U and

Y5V dielectrics are good for providing high capacitance in

a small package, but exhibit strong voltage and tempera-

ture coefficients as shown in Figures 3 and 4. When used

with a 5V regulator, a 10µF Y5V capacitor can exhibit an

effective value as low as 1µF to 2µF over the operating

temperature range. The X5R and X7R dielectrics result in

more stable characteristics and are more suitable for use

as the output capacitor. The X7R type has better stability

across temperature, while the X5R is less expensive and

is available in higher values.

50

TEMPERATURE (°C)

100 125

–50 –25

0

25

75

1962 F04

Figure 4. Ceramic Capacitor Temperature Characteristics

similar to the way a piezoelectric accelerometer or micro-

phone works. For a ceramic capacitor the stress can be

induced by vibrations in the system or thermal transients.

The resulting voltages produced can cause appreciable

amounts of noise, especially when a ceramic capacitor is

used for noise bypassing. A ceramic capacitor produced

Figure 5’s trace in response to light tapping from a pencil.

Similar vibration induced behavior can masquerade as

increased output voltage noise.

Voltage and temperature coefficients are not the only

sources of problems. Some ceramic capacitors have a

piezoelectric response. A piezoelectric device generates

voltage across its terminals due to mechanical stress,

LT1962-5

C_OUT= 10µF

C_BYP= 0.01µf

I_LOAD= 100mA

V_OUT

500µV/DIV

20

BOTH CAPACITORS ARE 16V,

1210 CASE SIZE, 10µF

0

X5R

–20

100ms/DIV

1962 F05

–40

Figure 5. Noise Resulting from Tapping on a Ceramic Capacitor

–60

Y5V

–80

Thermal Considerations

–100

The power handling capability of the device will be limited

by the maximum rated junction temperature (125°C). The

power dissipated by the device will be made up of two

components:

0

8

12 14

2

4

6

10

16

DC BIAS VOLTAGE (V)

1962 F04

Figure 3. Ceramic Capacitor DC Bias Characteristics

6

LT1962 Series

W U U

APPLICATIO S I FOR ATIO

U

1. Output current multiplied by the input/output voltage

The power dissipated by the device will be equal to:

I_OUT(MAX)(V_IN(MAX)– V_OUT) + I_GND(V_IN(MAX)

where,

I_OUT(MAX)= 100mA

_IN(MAX)= 6V

I_GNDat (I_OUT= 100mA, V_IN= 6V) = 2mA

So,

differential: (I_OUT)(V_IN– V_OUT), and

)

2. GND pin current multiplied by the input voltage:

(I_GND)(V_IN).

The GND pin current can be estimated using specification

in the Electrical Characteristics table. Power dissipation

will be equal to the sum of the two components listed

above.

V

P = 100mA(6V – 3.3V) + 2mA(6V) = 0.28W

The LT1962 series regulators have internal thermal limit-

ing designed to protect the device during overload condi-

tions. For continuous normal conditions, the maximum

junction temperature rating of 125°C must not be

exceeded. It is important to give careful consideration to

allsourcesofthermalresistancefromjunctiontoambient.

Additional heat sources mounted nearby must also be

considered.

The thermal resistance will be in the range of 110°C/W to

140°C/W depending on the copper area. So the junction

temperature rise above ambient will be approximately

equal to:

0.28W(125°C/W) = 35.3°C

The maximum junction temperature will then be equal to

the maximum junction temperature rise above ambient

plus the maximum ambient temperature or:

For surface mount devices, heat sinking is accomplished

by using the heat spreading capabilities of the PC board

and its copper traces. Copper board stiffeners and plated

through-holes can also be used to spread the heat gener-

ated by power devices.

T

_JMAX= 50°C + 35.3°C = 85.3°C

Protection Features

The LT1962 regulators incorporate several protection

featureswhichmakethemidealforuseinbattery-powered

circuits. In addition to the normal protection features

associated with monolithic regulators, such as current

limiting and thermal limiting, the devices are protected

against reverse input voltages, reverse output voltages

and reverse voltages from output to input.

The following table lists thermal resistance for several

different board sizes and copper areas. All measurements

were taken in still air on 1/16" FR-4 board with one ounce

copper.

Table 1. Measured Thermal Resistance

Current limit protection and thermal overload protection

areintendedtoprotectthedeviceagainstcurrentoverload

conditions at the output of the device. For normal opera-

tion, the junction temperature should not exceed 125°C.

COPPER AREA

THERMAL RESISTANCE

TOPSIDE* BACKSIDE

BOARD AREA (JUNCTION-TO-AMBIENT)

2500mm²

1000mm²

225mm²

100mm²

50mm²

2500mm²

110°C/W

115°C/W

120°C/W

130°C/W

140°C/W

The input of the device will withstand reverse voltages of

20V.Currentflowintothedevicewillbelimitedtolessthan

1mA (typically less than 100µA) and no negative voltage

will appear at the output. The device will protect both itself

and the load. This provides protection against batteries

which can be plugged in backward.

*Device is mounted on topside.

Calculating Junction Temperature

The output of the LT1962 can be pulled below ground

withoutdamagingthedevice.Iftheinputisleftopencircuit

or grounded, the output can be pulled below ground by

20V. For fixed voltage versions, the output will act like a

large resistor, typically 500k or higher, limiting current

Example: Given an output voltage of 3.3V, an input voltage

range of 4V to 6V, an output current range of 0mA to

100mA and a maximum ambient temperature of 50°C,

what will the maximum junction temperature be?

7

LT1962 Series

W U U

U

APPLICATIO S I FOR ATIO

flow to less than 40µA. For adjustable versions, the output

will act like an open circuit; no current will flow out of the

pin. If the input is powered by a voltage source, the output

will source the short-circuit current of the device and will

protect itself by thermal limiting. In this case, grounding

the SHDN pin will turn off the device and stop the output

from sourcing the short-circuit current.

voltage may be held up while the input is either pulled to

ground, pulledtosomeintermediatevoltageorisleftopen

circuit. Current flow back into the output will follow the

curve shown in Figure 6.

When the IN pin of the LT1962 is forced below the OUT pin

or the OUT pin is pulled above the IN pin, input current will

typicallydroptolessthan2µA. Thiscanhappeniftheinput

of the device is connected to a discharged (low voltage)

battery and the output is held up by either a backup battery

orasecondregulatorcircuit.ThestateoftheSHDNpinwill

have no effect on the reverse output current when the

output is pulled above the input.

The ADJ pin of the adjustable device can be pulled above

or below ground by as much as 7V without damaging the

device. Iftheinputisleftopencircuitorgrounded, theADJ

pin will act like an open circuit when pulled below ground

and like a large resistor (typically 100k) in series with a

diode when pulled above ground.

100

T

= 25°C

IN

J

V

In situations where the ADJ pin is connected to a resistor

divider that would pull the ADJ pin above its 7V clamp

voltage if the output is pulled high, the ADJ pin input

current must be limited to less than 5mA. For example, a

resistor divider is used to provide a regulated 1.5V output

fromthe1.22Vreferencewhentheoutputisforcedto20V.

The top resistor of the resistor divider must be chosen to

limitthecurrentintotheADJpintolessthan5mAwhenthe

ADJpinisat7V. The13VdifferencebetweenOUTandADJ

pin divided by the 5mA maximum current into the ADJ pin

yields a minimum top resistor value of 2.6k.

90

80

70

60

50

= 0V

CURRENT FLOWS

INTO OUTPUT PIN

V

= V

(LT1962)

OUT

ADJ

LT1962

LT1962-3

LT1962-3.3

LT1962-2.5

LT1962-5

40

30

20

10

0

1

2

3

4

5

6

7

8

9

10

OUTPUT VOLTAGE (V)

1962 F06

In circuits where a backup battery is required, several

different input/output conditions can occur. The output

Figure 6. Reverse Output Current

RELATED PARTS

PART NUMBER

LT1120

LT1121

LT1129

LT1175

LT1521

LT1529

LTC1627

LT1761

LT1762

LT1763

LT1764

LT1772

LT1963

DESCRIPTION

COMMENTS

125mA Low Dropout Regulator with 20µA I

Includes 2.5V Reference and Comparator

Q

150mA Micropower Low Dropout Regulator

30µA I , SOT-223 Package

Q

700mA Micropower Low Dropout Regulator

50µA Quiescent Current

500mA Negative Low Dropout Micropower Regulator

300mA Low Dropout Micropower Regulator with Shutdown

45µA I , 0.26V Dropout Voltage, SOT-223 Package

Q

15µA I , Reverse Battery Protection

Q

3A Low Dropout Regulator with 50µA I

500mV Dropout Voltage

Burst Mode^TMOperation, Monolithic, 100% Duty Cycle

Q

High Efficiency Synchronous Step-Down Switching Regulator

100mA, Low Noise, Low Dropout Micropower Regulator in SOT-23

150mA, Low Noise, LDO Micropower Regulator

20µA Quiescent Current, 20µV

25µA Quiescent Current, 20µV

30µA Quiescent Current, 20µV

340mV Dropout Voltage

Noise

RMS

500mA, Low Noise, LDO Micropower Regulator

3A, Fast Transient Response Low Dropout Regulator

Constant Frequency Current Mode Step-Down DC/DC Controller

1.5A, Fast Transient Response Low Dropout Regulator

Up to 94% Efficiency, SOT-23 Package, 100% Duty Cycle

SO-8, SOT-223 Packages

Burst Mode is a trademark of Linear Technology Corporation.

1962i LT/TP 0400 4K • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

8

●

(408)432-1900 FAX:(408)434-0507 www.linear-tech.com

LINEAR TECHNOLOGY CORPORATION 2000


型号：	LT1962EMS8
厂家：	Linear
描述：	300mA, Low Noise, Micropower LDO Regulators 300mA，低噪声，微功率LDO稳压器线性稳压器IC 电源电路
文件：	总8页 (文件大小：142K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LT1962EMS8 [Linear]

相关型号：

LT1962EMS8#PBF

LT1962EMS8#TR

LT1962EMS8#TRPBF

LT1962EMS8-1.5

LT1962EMS8-1.5#PBF

LT1962EMS8-1.5#TR

LT1962EMS8-1.5#TRPBF

LT1962EMS8-1.8

LT1962EMS8-1.8#PBF

LT1962EMS8-1.8#TR

LT1962EMS8-1.8#TRPBF

LT1962EMS8-2.5