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MIC2954
250mA Low-Dropout Regulator
General Description
The MIC2954 is a "bulletproof" efficient voltage regulator with very low dropout voltage (typically 40mV @ light loads and 375mV @ 250mA), and low quiescent current (120A typical). The quiescent current of the MIC2954 increases only slightly in dropout, thus prolonging battery life. Key MIC2954 features include protection against reversed battery, fold-back current limiting, and automotive load dump protection (60V positive transient). The MIC2954-07/08BM is an adjustable version that includes an error flag output that warns of a low output voltage, which is often due to failing batteries on the input. This may also be used as a power-on reset. A logiccompatible shutdown input is provided which enables the regulator to be switched on and off. This part may be pinstrapped for 5V output, or programmed from 1.24V to 29V with the use of two external resistors. The MIC2954 is available in two voltage tolerances, 0.5% maximum and 1% maximum. Both are guaranteed for junction temperatures from -40C to +125C. Data sheets and support documentation can be found on Micrel's web site at www.micrel.com.
Features
* * * * * * * * * * * High-accuracy 5V, guaranteed 250mA 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 Error flag warns of low output voltage Logic-controlled electronic shutdown Output programmable from 1.24V to 29V (MIC2954-07/08) Available in TO-220, TO-92, and surface-mount SOT223 and SOIC-8 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 ___________________________________________________________________________________________________________
Ordering Information
Part Number Pb-Free / Standard RoHS Compliant MIC2954-02BT MIC2954-02WT* MIC2954-03BT MIC2954-03WT* MIC2954-02BS MIC2954-02WS* MIC2954-03BS MIC2954-03WS* MIC2954-02BZ MIC2954-02YZ MIC2954-03BZ MIC2954-03YZ MIC2954-07BM MIC2954-07YM MIC2954-08BM MIC2954-08YM Accuracy 0.5% 1.0% 0.5% 1.0% 0.5% 1.0% 0.5% 1.0% Junction Temp. 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 Package TO-220-3 TO-220-3 SOT-223-3 SOT-223-3 TO-92-3** TO-92-3** 8-Pin SOIC 8-Pin SOIC
* RoHS compliant with `high-melting solder' exemption. ** TO-92 package discontinuance notification issued September 2007. End-of-life-buy offered thru December 31, 2007. Contact factory for additional information. 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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MIC2954
Typical Application
100k VIN
SHUTDOWN ENABLE
VERR VOUT 1.2V to 30V R1 100pF 10F R2
MIC2954
8 3
IN OUT SHDN ERR GND FB
1 5 7
R1 VOUT = VREF 1+ R2
5V Fixed Regulator
4
VREF
2, 6 = OPEN
Adjustable Regulator
5V or 3V Selectable Regulator with Shutdown
Wide Input-Voltage-Range Current Limiter
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MIC2954
Pin Configuration
OUT 1 SNS 2 SHDN 3 GND 4 8 IN 7 FB 6 TAP 5 ERR
1 IN
2
3
GND OUT
8-Pin SOIC (M)
3-Pin SOT-223 (S)
3 2 TO-92 1
OUT
3
TAB
OUT GND IN
GND IN
2 1
3-Pin TO-220 (T)
3-Pin TO-92 (Z)
Pin Description
Pin No. SOIC-8
8 4 1 2
Pin No. SOT-223
1 2, TAB 3
Pin No. TO-92
1 2 3
Pin No. TO-220
1 2 3
Pin Name
IN GND OUT SNS
Pin Name
Supply Input. Ground. Regulator Output. Sense (Input): Output-sense-voltage end of internal resistive divider. Connect to OUT (VOUT = 5V) for fixed5V operation; also see TAP. Not used in adjustable configuration. Shutdown (Input): Active-low input enables regulator. (Low = enable; high = shutdown.) Error Flag (Output): Open collector (active-low) output. Active state indicates an output (VOUT) undervoltage condition. (Low = error, floating = normal.) Divider Tap (Output): Resistive voltage divider tap. With 5Vapplied to SNS, VTAP is approximately 1.23V. Connect to FB for 5V operation. Not used in adjustable configuration. Feedback (Input): Error amplifier input. Compared to internal1.23V reference. Connect to external voltage divider for adjustable operation or internal voltage divider (TAP) for 5V operation (see SNS, TAP).
3 5
SHDN /ERR
6
TAP
7
FB
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MIC2954
Absolute Maximum Ratings(1)
Supply Voltage (VIN) ....................................... -20V to +60V Feedback Voltage (VFB) (14, 15)........................ -1.5V to +26V Shutdown Input Voltage (VSHDN).................... -0.3V to +30V Error Output Voltage (VERR) .......................... -0.3V to +30V Power Dissipation (PD) (4) ..........................Internally Limited Lead Temperature (soldering, 5 sec.)........................ 260C Storage Temperature (Ts) .........................-65C to +150C ESD Rating(3)
Operating Ratings(2)
Supply Voltage (VIN)...................................... +2.0V to +30V Junction Temperature (TJ) ........................ -40C to +125C Package Thermal Resistance (JC, JA) (5)
Electrical Characteristics
MIC2954-07/08: VFB = VTAP; VSNS = VOUT; VSHDN 0.6V. All versions: VIN = 6V; IL = 1mA; CL = 2.2F; TJ = 25C, bold values indicate -40C TJ +125C; Note 8; unless noted.
Symbol
VOUT
Parameter
Output Voltage
Condition
MIC2954-02/-07 (0.5%) MIC2954-02/-07 (0.5%), 1mA IL 250mA MIC2954-03/-08 (1%) MIC2954-03/-08 (1%), 1mA IL 250mA
Min
4.975 4.940
Typ
5.000
Max
5.025 5.060
Units
V V V V V V ppm/C ppm/C %/V %/V %/V %/V %/V %/V %/V %/V mV mV mV mV mV mV mV mV A A mA mA mA mA mA mA A
4.930
4.950 4.900
5.000
5.000
5.070
5.050 5.100
4.880
5.000 20 20
0.03 0.03 0.04 0.04 60 220 250 375 140 0.5 1.7 5 180
5.120 100 150
0.10 0.20 0.20 0.40 0.16 0.20 0.20 0.30 100 150 250 420 300 450 450 600 200 300 1 2 2.5 3.5 9 12
VOUT/T VOUT/VOUT
Output Voltage Temperature Coefficient, Note 6 Line Regulation, Note 7
MIC2954-02/-07 (0.5%) MIC2954-03/-08 (1%) MIC2954-02/-07 (0.5%), VIN = 6V to 26V MIC2954-03/-08 (1%), VIN = 6V to 26V
VOUT/VOUT
Load Regulation, Note 8
MIC2954-02/-07 (0.5%), IL = 1 to 250mA MIC2954-03/-08 (1%), IL = 1 to 250mA
VIN - VOUT
Dropout Voltage, Note 9
IL = 1mA IL = 50mA IL = 100mA IL = 250mA
IGND
Ground Pin Current, Note 10
IL = 1mA IL = 50mA IL = 100mA IL = 250mA
IGND(DO)
Ground Pin Current at Dropout, Note 10
VIN = 4.5V
300
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MIC2954
Symbol
ILIMIT VOUT/PD en
Parameter
Current Limit, Note 11 Thermal Regulation, Note 12 Output Noise Voltage (10Hz to 100kHz) Reference Voltage
Condition
VOUT = 0V
Min
Typ
Max
750 800
Units
mA mA %/W VRMS VRMS
0.05 IL = 100mA, CL = 2.2F IL = 100mA, CL = 33F MIC2954-02/-07 (0.5%) MIC2954-03/-08 (1%) 1.220 1.200 1.210 1.200 400 260 1.235 1.235
0.2
1.250 1.260 1.260 1.270
V V V V V V nA nA ppm/C ppm/C
Reference Voltage Feedback Pin Bias Current Reference Voltage Temperature Coefficient, Note 12 Feedback Pin Bias Current Temperature Coefficient
MIC2954-02/-07 (0.5%), Note 13 MIC2954-03/-08 (1%), Note 13
1.190 1.185
20
1.270 1.285
40 60
MIC2954-02/-07 (0.5%) MIC2954-03/-08 (1%)
20 50 0.1 40
nA/C
Error Comparator
Output Leakage Current Output Low Voltage Upper Threshold Voltage Lower Threshold Voltage Hysteresis VOH = 30V VIN = 4.5V, IOL = 400A 0.01 150 60 75 15 1.00 2.00 250 400 40 25 95 140 A A mV mV mV mV mV mV mV mV
Note 14 Note 14 Note 14
Shutdown Input
Input Logic Voltage Shutdown Pin Input Current low (on) high (off) VSHDN = 2.4V VSHDN = 30V Regular Output Current in Shutdown 2.0 30 450 3 50 100 600 750 10 20 1.3
0.7
V V A A A A A A
Note 15
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Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. 4. PD(max) = (TJ(max) - TA) / JC. Exceeding TJ(max) will cause thermal shutdown.
MIC2954
5. Thermal resistance (JC) of the TO-220 package is 2.5C/W, and 15C/W for the SOT-223. Thermal resistance (JC) of the TO-92 package is 180C/W with 0.4" leads and 160C/W with 0.25" leads. Thermal resistance (JA) of the SOP-8 is 160C/W mounted on a printed circuit board (See "Application Information: Thermal Calculation"). 6. Output voltage temperature coefficient is defined as the worst case voltage change divide by the total temperature range. 7. Line regulation for the MIC2954 is tested at 125C for IL = 1mA. For IL = 100A and TJ = 125C, line regulation is guaranteed by design to0.2%. See "Typical Characteristics" for line regulation versus temperature and load current. 8. 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. 9. 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 very low values of programmed output voltage, the minimum input supply voltage of 2 V (2.3V over temperature) must be taken into account. 10. 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. 11. The MIC2954 features fold-back current limiting. The short circuit (VOUT = 0V) current limit is less than the maximum current with normal output voltage. 12. 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. 13. VREF VOUT (VIN - 1V), 2.3V VIN 30V, 100 A < IL 250 mA, TJ TJ(max). 14. Comparator thresholds are expressed in terms of a voltage differential at the FB pin below the nominal reference voltage measured at 6Vinput. To express these thresholds in terms of output voltage change, multiply by the error amplifier gain = VOUT /VREF = (R1 + R2)/R2. For example, at a programmed output voltage of 5V, the error output is guaranteed to go low when the output drops by 95mV x 5V/1.235V = 384mV. Thresholds remain constant as a percent of VOUT as VOUT is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed. 15. VSHDN 2V, VIN 30 V,VOUT = 0, with the FB pin connected to TAP. 16. 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. 17. Maximum positive supply voltage of 60V must be of limited duration (<10ms) and duty cycle (<1%). The maximum continuous supply voltage is 30V.
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MIC2954
Typical Characteristics
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MIC2954
Typical Characteristics
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MIC2954
Functional Diagrams
Unregulated DC Supply
IN OUT Error Amp. 182k 62k 1.23V REF. 2.2F GND 5V/250mA Output
MIC2954-02/-03
MIC2954-02 and MIC2954-03
MIC2954-07 and MIC2954-08
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MIC2954 The error comparator has an open-collector output which requires an external pull-up resistor. Depending on system requirements, this resistor may be returned to the 5V output or some other supply voltage. In determining a value for this resistor, note that while the output is rated to sink 400A, this sink current adds to battery drain in a low battery condition. Suggested values range from 100k to 1M. The resistor is not required if this output is unused. Programming the Output Voltage (MIC2954-07/-08) The MIC2954-07/-08 may be pin-strapped for 5V using its internal voltage divider by tying pin 1 (OUT) to pin 2 (SNS) and pin 7 (FB) to pin 6 (TAP). Alternatively, it may be programmed for any output voltage between its 1.235V reference and its 30V maximum rating. An external pair of resistors is required, as shown in Figure 3. The complete equation for the output voltage is:
Application Information
External Capacitors A 2.2F (or greater) capacitor is required between the MIC2954 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 0.5F for current below 10mA or 0.15F for currents below 1mA. Adjusting the MIC295407/-08 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 250mA load at 1.23V output (output shorted to feedback) a 5F (or greater) capacitor should be used. The MIC2954 will remain in regulation with a minimum load of 1mA. When setting the output voltage of the MIC2954-07/-08 version with external resistors, the current through these resistors may be included as a portion of the minimum load. A 0.1F capacitor should be placed from the MIC2954 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. Error Detection Comparator Output (MIC2954-07/-08) A logic-low output will be produced by the comparator whenever the MIC2954-07/-08 output falls out of regulation by more than approximately 5%. This figure is the comparator's built-in offset of about 60mV divided by the 1.235V reference voltage. (Refer to the block diagram on page 1). This trip level remains "5% below normal" regardless of the programmed output voltage of the MIC2954-07/-08. For example, the error flag trip level is typically 4.75V for a 5V output or 11.4V for a12V output. The out of regulation condition may be due either to low input voltage, current limiting, or thermal limiting. Figure 1 is a timing diagram depicting the /ERR signal and the regulated output voltage as the MIC2954-07/-08 input is ramped up and down. The /ERR signal becomes valid (low) at about 1.3V input. It goes high at about 5V input (the input voltage at which VOUT = 4.75). Since the MIC2954-07/-08's dropout voltage is load-dependent (see curve in "Typical Characteristics"), the input voltage trip point (about 5V) will vary with the load current. The output voltage trip point (approximately 4.75V) does not vary with load. September 2007 10
R1 VOUT = VREF 1 + + IFB R1 R2
where: VREF = nominal 1.235V reference voltage IFB = nominal FB pin bias current (-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 MIC2954-07/-08 typically draws 60A at no load with pin 2 (SNS) opencircuited, this is a negligible addition. 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 fourfold by a bypass capacitor across R1, since it reduces the high frequency gain from 4 to unity. Pick:
C BYPASS 1 2R1 x 200Hz
M9999-090607
Micrel, Inc.
MIC2954
Thermal Calculations
Layout Considerations The MIC2954-07BM/-08BM (8-pin surface-mount package) has the following thermal characteristics when mounted on a single layer copper-clad printed circuit board. PC Board Dielectric Material JA FR4 160C/W Ceramic 120C/W Multilayer boards having a ground plane, wide traces near the pads, and large supply bus lines provide better thermal conductivity. Our calculations will use the "worst case" value of 160C/W, which assumes no ground plane, minimum trace widths, and a FR4 material board. Pad Layout (minimum recommended geometry)
* See Application Information
Figure 1. /Error Output Timing
or about 0.01F. When doing this, the output capacitor must be increased to 3.3F to maintain stability. These changes reduce the output noise from 430V to 100Vrms for a100kHz 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 MIC2954 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 (75A 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.
Nominal Power Dissipation and Die Temperature The MIC2954-07BM/-08BM at a 55C ambient temperature will operate reliably at up to 440mW power dissipation when mounted in the "worst case" manner described above. This power level is equivalent to a die temperature of 125C, the recommended maximum temperature for nonmilitary grade silicon integrated circuits.
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MIC2954
Schematic Diagram
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MIC2954
Package Information
8-Pin SOIC (M)
0.090 (2.286) Radius, t yp. 2 1 3 0.145 (3.683) 0.135 (3.429) 0.055 (1.397) 0.045 (1.143)
10 typ.
BOTTOM VIEW
0.085 (2.159) Diam . 0.185 (4.699) 0.175 (4.445) 5 typ.
0.185 (4.699) 0.175 (4.445)
0.090 (2.286) typ.
Seat ing Plane 0.025 (0.635) Max Uncont rolled Lead Diamet er 0.500 (12.70) Min.
5 typ.
0.016 (0.406) 0.014 (0.356) 0.055 (1.397) 0.045 (1.143) 0.105 (2.667) 0.095 (2.413) 0.0155 (0.3937 ) 0.0145 (0.3683 )
3-Pin TO-92 (Z)
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MIC2954
3-Pin SOT-223 (S)
3-Pin TO-220 (T)
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MIC2954
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) 2001 Micrel, Incorporated.
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