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MIC2940A/2941A
1.2A Low-Dropout Voltage Regulator
General Description
The MIC2940A and MIC2941A are "bulletproof" efficient voltage regulators with very low dropout voltage (typically 40mV at light loads and 350mV at 1A), and low quiescent current (240A typical). The quiescent current of the MIC2940A increases only slightly in dropout, thus prolonging battery life. Key MIC2940A features include protection against reversed battery, fold-back current limiting, and automotive "load dump" protection (60V positive transient). The MIC2940 is available in both fixed voltage (3.3V, 5V, and 12V) and adjustable voltage configurations. The MIC2940A-xx devices are three pin, fixed voltage regulators. A logic-compatible shutdown input is provided on the adjustable MIC2941A, which enables the regulator to be switched on and off. Data sheets and support documentation can be found on Micrel's web site at: www.micrel.com.
Features
* * * * * * * * High output voltage accuracy Guaranteed 1.25A output Low quiescent current Low dropout voltage Extremely tight load and line regulation Very low temperature coefficient Current and thermal limiting Input can withstand -20V reverse battery and +60V positive transients * Logic-controlled electronic shutdown * Output programmable from 1.24V to 26V(MIC2941A) * Available in TO-220, TO-263, TO-220-5, and TO-263-5 packages.
Applications
* Battery powered equipment * Cellular telephones * Laptop, notebook, and palmtop computers * PCMCIA VCC and VPP regulation/switching * Bar code scanners * Automotive electronics * SMPS post-regulator/ DC-to-DC modules * Voltage reference * High efficiency linear power supplies ___________________________________________________________________________________________________________
Pin Configuration
1
2
3
1
23
4
5
TO-263-3 (MIC2940A-xxBU/WU)
1 2 3
TO-263-5 (MIC2941ABU/WU)
MIC2941A Pinout 1) Adjust 2) Shutdown 3) Ground 4) Input 5) Output
1234 5
TO-220-3 (MIC2940A-xxBT/WT)
MIC2940A Pinout 1) Input 2) Ground 3) Output
TO-220-5 (MIC2941ABT/WT)
The TAB is Ground on TO-220 and TO-263 packages Micrel Inc. * 2180 Fortune Drive * San Jose, CA 95131 * USA * tel +1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com
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Micrel, Inc.
MIC2940A/2941A
Ordering Information
Part Number MIC2940A-3.3BT MIC2940A-3.3BU MIC2940A-3.3WT MIC2940A-3.3WU MIC2940A-5.0BT MIC2940A-5.0BU MIC2940A-5.0WT MIC2940A-5.0WU MIC2940A-12BT MIC2940A-12BU MIC2940A-12WT MIC2940A-12WU MIC2941ABT MIC2941ABU MIC2941AWT MIC2941AWU
Note: 1. RoHS compliant with `hot-melting solder' exemption.
Voltage 3.3V 3.3V 3.3V 3.3V 5V 5V 5V 5V 12V 12V 12V 12V Adj. Adj. Adj. Adj.
Temperature Range -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C
Package 3-Pin TO-220 3-Pin TO-263 3-Pin TO-220 3-Pin TO-263 3-Pin TO-220 3-Pin TO-263 3-Pin TO-220 3-Pin TO-263 3-Pin TO-220 3-Pin TO-263 3-Pin TO-220 3-Pin TO-263 5-Pin TO-220 5-Pin TO-263 5-Pin TO-220 5-Pin TO-263
Lead Finish Standard Standard RoHS Comliant(1) RoHS Comliant(1) Standard Standard RoHS Comliant(1) RoHS Comliant(1) Standard Standard RoHS Comliant(1) RoHS Comliant(1) Standard Standard RoHS Comliant(1) RoHS Comliant(1)
Schematic Diagram
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MIC2940A/2941A Input Supply Voltage ...................................... -20V to +60V Operating Input Supply Voltage .......................... 2V to 26V Adjust Input Voltage (Notes 9 and 10) ......... -1.5V to +26V Shutdown Input Voltage ................................ -0.3V to +30V Error Comparator Output Voltage ................. -0.3V to +30V
Absolute Maximum Ratings
If Military/Aerospace specified devices are required, contact your local Micrel representative/distributor for availability and specifications Power Dissipation (Note 1) .......................Internally Limited Lead Temperature (soldering, 5 sec.)........................ 260C Storage Temperature ................................-65C to +150C Operating Junction Temperature ..............-40C to +125C TO-220 (JC) ........................................................2C/W TO-263 (JC) ........................................................2C/W
Across the full operating temperature, the minimum input voltage range for full output current is 4.3V to 26V. Output will remain in-regulation at lower output voltages and low current loads down to an input of 2V at 25C.
Electrical Characteristics
Limits in standard typeface are for TJ = 25C and limits in boldface apply over the full operating temperature range. Unless otherwise specified, VIN = VOUT + 1V, IL = 1000mA, CL = 10F. The MIC2941A is programmed to output 5V and has VSHUTDOWN 0.6V.
Symbol VO Parameter Output Voltage Accuracy 5 mA IL 1A VO T VO VO VIN - VO Output Voltage Temperature Coefficient Line Regulation Load Regulation Dropout Voltage (Note 4) (Note 2) IO = 10mA, (VOUT + 1V) VIN 26V IL = 5mA to 1.25A IL = 5mA to 1A (Note 3) IL = 5mA IL = 250mA IL = 1000mA IL = 1250mA IGND Ground Pin Current (Note 5) IL = 5mA IL = 250mA IL = 1000mA IL = 1250mA IGNDDO ILIMIT VO PD en Ground Pin Current at Dropout (Note 5) Current Limit Thermal Regulation Output Noise Voltage (10Hz to 100kHz) IL = 100mA VIN = 0.5V less than designed VOUT (VOUT 3.3) IL = 5mA VOUT = 0V (Note 6) (Note 7) CL = 10F CL = 33F Condition Min -1 -2 -2.5 20 0.06 0.04 60 200 350 400 240 3 22 35 330 1.6 0.05 400 260 Typ Max 1 2 2.5 100 0.50 0.16 0.20 150 180 250 320 450 600 600 500 4.5 6 35 45 70 600 3.5 0.2 Units % % % ppm/C % % % mV mV mV mV mV mV mV A mA mA mA mA mA A A %/W VRMS VRMS
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MIC2940A/2941A
Electrical Characteristics (MIC2941A Only)
Parameter Reference Voltage (Note 8) Adjust Pin Bias Current Reference Voltage Temperature Coefficient Adjust Pin Bias Current Temperature Coefficient Shutdown Input Input Logic Voltage Low (ON) High (OFF) Shutdown Pin Input Current VSHUTDOWN = 2.4V VSHUTDOWN = 26V Regulator Output Current in Shutdown
Notes: 1. Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its rated operating conditions. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX), the junction-to-ambient thermal resistance, JA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: P(MAX) = (TJ(MAX) - TA) / JA. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Changes in output voltage due to heating effects are covered by the thermal regulation specification. Dropout Voltage is defined as the input to output differential at which the output voltage drops 100 mV below its nominal value measured at 1V differential. At low values of programmed output voltage, the minimum input supply voltage of 4.3V over temperature must be taken into account. Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current plus the ground pin current. The MIC2940A features fold-back current limiting. The short circuit (VOUT = 0V) current limit is less than the maximum current with normal output voltage. Thermal regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, excluding load or line regulation effects. Specifications are for a 200mA load pulse at VIN = 20V (a 4W pulse) for T = 10ms. VREF VOUT (VIN - 1 V), 4.3V VIN 26V, 5mA < IL 1.25A, TJ TJ(MAX). Circuit of Figure 3 with R1 150k . VSHUTDOWN 2 V and VIN 26 V,VOUT = 0.
Condition
Min 1.223 1.210 1.204
Typ 1.235
Max 1.247 1.260 1.266 40 60
Units V V V nA nA ppm/C nA/C
20 20 0.1
1.3 0.7 2.0 30 450 3 50 100 600 750 30 60
V V V A A A A A A
(Note 10)
2. 3. 4. 5. 6. 7. 8. 9.
10. When used in dual supply systems where the regulator load is returned to a negative supply, the output voltage must be diode clamped to ground. 11. Maximum positive supply voltage of 60 V must be of limited duration (< 100 ms) and duty cycle ( 1%). The maximum continuous supply voltage is 26V.
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MIC2940A/2941A
Typical Characteristics
500 DROPOUT VOLTAGE (mV) 400 300 200 100 0 0.00
Dropout Voltage vs. Output Current
DROPOUT VOLTAGE (mV)
1000 800 600 400 200
Dropout Voltage vs. Temperature
OUTPUT VOLTAGE (V)
6 5 4 3 2 1 0 0
Dropout Characteristics
ILOAD = 5mA
ILOAD = 1.25A
ILOAD = 1.25A
0.25 0.50 0.75 1.00 OUTPUT CURRENT (A)
1.25
0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
1 2 3 4 5 INPUT VOLTAGE (V)
6
40 GROUND CURRENT (mA) 10
Ground Current vs. Output Current
GROUND CURRENT (A)
400
Ground Current vs. Supply Voltage
GROUND CURRENT (mA)
50 40 30 20 10 0
Ground Current vs. Supply Voltage
300
200
1
100
FIXED 5V ILOAD = 5mA 0 1 234567 SUPPLY VOLTAGE (V) 8
FIXED 3.3V DEVICE ILOAD = 1.25A 0 2 4 6 8 INPUT VOLTAGE (V) 10
0.1
11
0 100 1000 10000 10A OUTPUT CURRENT (mA)
0
0.40 GROUND CURRENT (mA)
Ground Current vs. Temperature
GROUND CURRENT (mA)
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2
Ground Current vs. Temperature
GROUND CURRENT (mA)
50 40 30 20 10
Ground Current vs. Temperature
ILOAD = 1.25A
0.30
0.20
ILOAD = 100mA
0.10
ILOAD = 5mA
ILOAD = 100mA 0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
0.00 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
0.0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
3.40 OUTPUT VOLTAGE (V) 3.38 3.36
Fixed 3.3V Output Voltage vs. Temperature
2.0 1.8 1.6 CURRENT (A) 1.4 1.2 1.0 0.8 0.6 0.4 0.2
Short Circuit and Maximum Current vs. Temperature
GROUND CURRENT (A)
1000 800 600 400 200 0 -200 -30
Ground Current vs. Input Voltage
RLOAD = 100
VOUT = VNOMINAL - 0.5V
3.34 3.32 3.30 3.28 3.26 3.24 3.22 3.20 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
VOUT = 0V FIXED 3.3V VERSION 3 SAMPLES
0.0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
-20 -10 0 10 20 INPUT VOLTAGE (V)
30
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MIC2940A/2941A
Typical Characteristics (continued)
OUTPUT (mV)
125 ENABLE CURRENT (A) 100 VE N = 5V 75 50 VE N = 2V 25 0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
MIC29401/2 Shutdown Current vs. Temperature
OUTPUT (mV)
750 500 250 0 -250
Load Transient
COUT = 10 F
200 100 0 -100
Load Transient
COUT = 100 F
-500 2.0 1.5 1.0 5mA 0.5 0.0 -0.5 -5
0 5 TIME (ms)
10
-200 2.0 1.5 1.0 5mA 0.5 0.0 -0.5 -5
OUTPUT (A)
OUTPUT (A)
0 5 TIME (ms)
10
OUTPUT (mV)
ADJUST PIN CURRENT (nA)
20 0 -20 10 -40
COUT = 10 F
OUTPUT (mV)
50 40 30 20 10
MIC29402/3 Adjust Pin Current vs. Temperature
40
Line Transient
20 10 0 10 -10
Line Transient
COUT = 100 F
INPUT (V)
INPUT (V)
8 6 4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 TIME (ms)
8 6 4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 TIME (ms)
ILOAD = 5mA
0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
10 OUTPUT IMPEDANCE ( )
Output Impedance vs. Frequency
1
0.1 ILOAD = 10mA 0.01
1x100
1x103
100x100
FREQUENCY (Hz)
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10x100
10x103
1x106
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MIC2940A/2941A Reducing Output Noise In reference applications it may be advantageous to reduce the AC noise present at the output. One method is to reduce the regulator bandwidth by increasing the size of the output capacitor. This is relatively inefficient, as increasing the capacitor from 1F to 220F only decreases the noise from 430V to 160VRMS for a 100kHz bandwidth at 5V output. Noise can be reduced by a factor of four with the MIC2941A by adding a bypass capacitor across R1. Pick
C BYPASS 1 2R 1 200Hz
Application Information
External Capacitors A 10F (or greater) capacitor is required between the MIC2940A output and ground to prevent oscillations due to instability. Most types of tantalum or aluminum electrolytics will be adequate; film types will work, but are costly and therefore not recommended. Many aluminum electrolytics have electrolytes that freeze at about -30C, so solid tantalums are recommended for operation below -25C. The important parameters of the capacitor are an effective series resistance of about 5 or less and a resonant frequency above 500kHz. The value of this capacitor may be increased without limit. At lower values of output current, less output capacitance is required for output stability. The capacitor can be reduced to 3.3F for current below 100mA or 2.2F for currents below 10mA. Adjusting the MIC2941A to voltages below 5V runs the error amplifier at lower gains so that more output capacitance is needed. For the worst-case situation of a 1.25A load at 1.23V output (Output shorted to Adjust) a 22F (or greater) capacitor should be used. The MIC2940A will remain stable and in regulation with load currents ranging from 5mA on up to the full 1.25A rating. The external resistors of the MIC2941A version may be scaled to draw this minimum load current. A 0.22F capacitor should be placed from the MIC2940A input to ground if there is more than 10 inches of wire between the input and the AC filter capacitor or if a battery is used as the input. Programming the Output Voltage (MIC2941A) The MIC2941A may be programmed for any output voltage between its 1.235V reference and its 26V maximum rating. An external pair of resistors is required, as shown in Figure 3. VOUT = VREF x { 1 + R1/R2 } - |IFB| R1 where VREF is the nominal 1.235 reference voltage and IFB is the Adjust pin bias current, nominally 20nA. The minimum recommended load current of 1A forces an upper limit of 1.2M on the value of R2, if the regulator must work with no load (a condition often found in CMOS in standby), IFB will produce a -2% typical error in VOUT which may be eliminated at room temperature by trimming R1. For better accuracy, choosing R2 = 100k reduces this error to 0.17% while increasing the resistor program current to 12A. Since the MIC2941A typically draws 100A at no load with SHUTDOWN opencircuited, this is a negligible addition.
or about 0.01F. When doing this, the output capacitor must be increased to 22F to maintain stability. These changes reduce the output noise from 430V to 100VRMS for a 100kHz bandwidth at 5V output. With the bypass capacitor added, noise no longer scales with output voltage so that improvements are more dramatic at higher output voltages.
Automotive Applications The MIC2940A is ideally suited for automotive applications for a variety of reasons. It will operate over a wide range of input voltages with very low dropout voltages (40mV at light loads), and very low quiescent currents (240A typical). These features are necessary for use in battery powered systems, such as automobiles. It is a "bulletproof" device with the ability to survive both reverse battery (negative transients up to 20V below ground), and load dump (positive transients up to 60V) conditions. A wide operating temperature range with low temperature coefficients is yet another reason to use these versatile regulators in automotive designs.
4.75V OUTPUT VOLTAGE
ERROR
NOT * VALID
NOT * VALID
INPUT VOLTAGE
5V 1.3V
Figure 1. ERROR Output Timing
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MIC2940A/2941A
Typical Applications
V IN
+VIN
+VIN V OUT
+
VIN
VOUT V OUT 1.2V 26V
VOUT = 5V
S HUTDOWN INPUT
ON
10F
SHUTDOWN GND AD JU S T
OFF
R1 100 pF
22F
GND
V OUT = V R E F x (1 + R1 ) R2
1.23V
VREF R2
Figure 2. MIC2940A-5.0 Fixed +5V Regulator
Figure 3. MIC2941A Adjustable Regulator
+V IN
+5V to +7V
V IN VOUT
+V IN
V CC OUT VOUT
V OUT = V IN
SHUTDOWN INPUT OFF ON
SHUTDOWN + 100pF GND ADJ 300k 1% 10F
GND
ADJUST
3.3V
5V
470 k
220k 1% 2N2222
180k 1%
* Minimum Input-Output Voltage Ranges from 40mV to 400mV, depending on Load Current.
Adjust Pin Low = Enable Output. Q1 ON = 3.3V, Q1 OFF = 5.0V.
Figure 4. MIC2941A Wide Input Voltage Range Current Limit
Figure 5. MIC2941A 5.0V or 3.3V Selectable Regulator with Shutdown
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MIC2940A/2941A
Package Information
3-Pin TO-220 (T)
3-Pin TO-263 (U)
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MIC2940A/2941A
5-Pin TO-220 (T)
5-Pin TO-263 (U)
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MIC2940A/2941A
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. (c) 2004 Micrel, Incorporated.
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