.ixed 5.0V Adjustable 100mA Voltage Regulator Guaranteed 100mA cu

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.ixed 5.0V Adjustable 100mA Voltage Regulator Guaranteed 100mA cu

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LP2951 power voltage regulator quiescent current dropout voltage. quiescent current increases minimally during dropout conditions thereby extending battery life. Refer LP2951A data sheet 150mA version with tighter regulation. Available lead SOIC package, LP2951 includes features such shutdown output voltage detect (typically battery conditions). This function also used power reset function when triggered CMOS inputs. circuit used fixed voltage volt regulator adjusted between 1.24 volts volts using external resistor pairs.
.ixed 5.0V Adjustable 100mA Voltage Regulator
Guaranteed 100mA current Adjustable output voltage 1.24V Accurate output dropout voltage 380mV 100mA Regulator reference functions .ull industrial temperature range SO-8 package
LP2951
Applications
Microcontroller supplies Linear regulators Adjustable Supplies Switching power supplies post-regulation Portable modems Battery powered systems Cellular telephones Voltage references
Typical Application Circuits
10nF
VOUT 1.24V SHUTDOWN INPUT
LP2951 ERRORB ERROR OUTPUT
SENSE SHDN
VOUT VREF
3.3uF
100k
VOUT SHUTDOWN INPUT 3.3uF
LP2951 ERRORB ERROR OUTPUT
SENSE SHDN
100k
Revision August 2001
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LP2951
POWER MANAGEMENT Absolute Maximum Ratings
Parameter Supply Voltage Shutdown Input Voltage Error Comp. Output Voltage Power Dissipation Thermal Resistance Junction Case Thermal Resistance Junction Ambient(1) Operating Junction Temperature Range Storage Temperature Range Lead Temperature (Soldering) Sec. Rating (Human Body Model) TSTG TLEAD Symbol VSHDN Maximum -0.3 -0.3 -0.3 Internally Limited Units °C/W °C/W
Note: inch square 1/16 .R4, double sided, 1oz. minimum copper weight.
Electrical Characteristics
Unless specified: VOUT(NOM) IOUT 100µA,
1µF, limits over operating temperature range TA).
Parameter Output Voltage Temp Coefficient Line Regulation Load Regulation Dropout Voltage
Symbol REG(LINE) REG(LOAD)
Conditions 25°C, IOUT 100µA 70°C (VOUT(NOM) 100µA IOUT 100mA IOUT 100µA IOUT 100mA
4.950
5.000
5.050 1.260
Units ppm/°C
Ground Current
IGND
IOUT 100µA IOUT 100mA
Dropout Ground Current Short Circuit Current Limit Reference Voltage Feedback Bias Current
IGND(D) VREF
(VOUT(NOM) 0.5V), IOUT 100µA VOUT VREF VOUT (VIN 1V), 25°C, 100µA IOUT 100mA 1.210
1.235
2001 Semtech Corp.
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LP2951
POWER MANAGEMENT Electrical Characteristics (Cont.)
Unless specified: VOUT(NOM) IOUT 100µA, COUT 1µF, limits over operating temperature range TA).
Parameter Error Comparator Output High Leakage Current Output Voltage Threshold Voltage
Symbol
Conditions
Units
IL(OH)
(VOUT(NOM) 0.5V), 400µA Upper Lower
Hysteresis Shutdow Input Input Logic Voltage
VHYST
VSHDN
High
Input Current
ISHDN
VSHDN 2.4V VSHDN
Regulator Shutdown Output Current
IOUT(SHDN)
VSHDN 30V, VOUT Feedback
Note: Temperature coefficient defined worst case voltage change divided total temperature range.
2001 Semtech Corp.
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LP2951
POWER MANAGEMENT Configuration Ordering Information
Device(1) LP2951CM.TR Output Voltage 5V/ADJ ackag SO-8
Notes: Only available tape reel packaging. reel contains 2500 devices.
Block Diagram
2001 Semtech Corp.
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LP2951
POWER MANAGEMENT Applications Information (LP2951(A))
Setting Output Voltage LP2951(A) deliver output voltage from 1.24V using external voltage divider. addition, internal voltage divider provided output desired. internal voltage divider, simply connect sense output feedback (see block diagram). When using external divider sense pins left open, divider installed from output ground, with center connected feedback (see Adjustable Regulator figure below). When using external voltage divider, resistances calculated from following formula:
VOUT .235 .235
Theoretically, also possible regulator become unstable very large capacitances (>10,000µ.) connected output, this been observed practice. also important that capacitance mounted close (1cm less) output regulator.
upper limit values occurs ~1.2M regulator operated when completely unloaded, this allows feedback divider provide minimum load recommended LP2951(A). regulator always load more connected externally, higher resistor values used, attention must paid -20nA (typical) bias current required feedback pin. Using 1.2M resistor this bias current will already cause shift output voltage between full load load. Larger values exacerbate problem. Using 120k resistor reduces error caused feedback bias current 0.2% while still only requiring 10µA feed divider string. Output .iltering output filter capacitor always necessary with LP2951(A) order assure output stability. size this capacitor varies with output voltage (smaller higher output voltages) output current (smaller lower output currents). operation sufficient. regulator operation minimum output voltage (1.24V) output currents 100mA, required filter increases 3.3µ. type capacitor used, although aluminum electrolytics chosen, equivalent series resistance (ESR) should held less. small load currents capacitance reduced. 0.33µ. will satisfactory output currents 10mA less, 0.1µ. will work output current below 1mA.
2001 Semtech Corp.
.igure Adjustable Regulator lead inductance between input LP2951(A) power source exceeds ~500nH (approximately 10/25cm 0.031/0.78mm trace) also necessary filter capacitor between input terminal ground. tantalum aluminum electrolytic capacitor usually sufficient. Lower values used load currents small. Noise injection into feedback terminal LP2951(A) from nearby noise sources also upset output. Generally this cured addition 100p. from feedback terminal output. Reducing Output Noise ultra-quiet systems, when LP2951(A) being used reference, desirable perform additional output filtering reduce noise. While this done simply using larger capacitors output, that solution tends bulky expensive, eventually, with huge capacitors (>1,000µ.) cause instability regulator. Generally, more cost-effective regulator regulate output noise away.
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LP2951
POWER MANAGEMENT Applications Information (Cont.)
This done bypassing upper resistor feedback divider with small capacitor provide more direct path feedback. size this capacitor calculated from formula: CBYPASS corner where upper resistor feedback divider fcorner frequency above which increased feedback become active. Because gain error amplifier LP2951(A) begins roll about 300Hz, this generally optimum choice corner frequency. reduction output noise will proportional ratio resistors feedback divider:
will increase rate decade frequencies above corner frequency chosen, frequency where error amplifiers gain rolled (~100kHz). order maintain regulator stability when using noise-reducing bypass capacitor, will also necessary increase size output filter capacitor ratio:
2001 Semtech Corp.
www.semtech.com
LP2951
POWER MANAGEMENT Outline Drawing SO-8
Land Pattern -SO-8
Contact Information
Semtech Corporation Power Management Products Division Mitchell Rd., Newbury Park, 91320 Phone: (805)498-2111 (805)498-3804
2001 Semtech Corp.
www.semtech.com

.ixed 5.0V Adjustable 100mA Voltage Regulator Guaranteed 100mA cu

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