MIC2940A/2941A. Features. General Description. Applications. Pin Configuration. 1.2A Low-Dropout Voltage Regulator

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1 MIC294A/2941A 1.2A Low-Dropout oltage Regulator General Description The MIC294A and MIC2941A are bulletproof efficient voltage regulators with very low dropout voltage (typically 4 at light loads and 35 at 1A), and low quiescent current (24 typical). The quiescent current of the MIC294A increases only slightly in dropout, thus prolonging battery life. Key MIC294A features include protection against reversed battery, fold-back current limiting, and automotive load dump protection (6 positive transient). The MIC294 is available in both fixed voltage (3.3, 5, and 12) and adjustable voltage configurations. The MIC294A-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: Features High output voltage accuracy Guaranteed 1.25A output Low quiescent current Low dropout voltage Extremely tight load and line regulation ery low temperature coefficient Current and thermal limiting Input can withstand 2 reverse battery and +6 positive transients Logic-controlled electronic shutdown Output programmable from 1.24 to 26(MIC2941A) Available in TO-22, TO-263, TO-22-5, and TO packages. Applications Battery powered equipment Cellular telephones Laptop, notebook, and palmtop computers PCMCIA CC and PP regulation/switching Bar code scanners Automotive electronics SMPS post-regulator/ DC-to-DC modules oltage reference High efficiency linear power supplies Pin Configuration TO (MIC294A-xxBU/WU) TO (MIC2941ABU/WU) MIC294A Pinout 1) Input 2) Ground 3) Output TO-22-3 (MIC294A-xxBT/WT) MIC2941A Pinout 1) Adjust 2) Shutdown 3) Ground 4) Input 5) Output The TAB is Ground on TO-22 and TO-263 packages TO-22-5 (MIC2941ABT/WT) Micrel Inc. 218 Fortune Drive San Jose, CA USA tel +1 (48) fax + 1 (48) July 27 M

2 MIC294A/2941A Ordering Information Part Number oltage Temperature Range Package Lead Finish MIC294A-3.3BT to +125 C 3-Pin TO-22 Standard MIC294A-3.3BU to +125 C 3-Pin TO-263 Standard MIC294A-3.3WT to +125 C 3-Pin TO-22 RoHS Comliant (1) MIC294A-3.3WU to +125 C 3-Pin TO-263 RoHS Comliant (1) MIC294A-5.BT 5 4 to +125 C 3-Pin TO-22 Standard MIC294A-5.BU 5 4 to +125 C 3-Pin TO-263 Standard MIC294A-5.WT 5 4 to +125 C 3-Pin TO-22 RoHS Comliant (1) MIC294A-5.WU 5 4 to +125 C 3-Pin TO-263 RoHS Comliant (1) MIC294A-12BT 12 4 to +125 C 3-Pin TO-22 Standard MIC294A-12BU 12 4 to +125 C 3-Pin TO-263 Standard MIC294A-12WT 12 4 to +125 C 3-Pin TO-22 RoHS Comliant (1) MIC294A-12WU 12 4 to +125 C 3-Pin TO-263 RoHS Comliant (1) MIC2941ABT Adj. 4 to +125 C 5-Pin TO-22 Standard MIC2941ABU Adj. 4 to +125 C 5-Pin TO-263 Standard MIC2941AWT Adj. 4 to +125 C 5-Pin TO-22 RoHS Comliant (1) MIC2941AWU Adj. 4 to +125 C 5-Pin TO-263 RoHS Comliant (1) Note: 1. RoHS compliant with hot-melting solder exemption. Schematic Diagram July 27 2 M

3 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.) C Storage Temperature C to +15 C Operating Junction Temperature... 4 C to +125 C TO-22 (θ JC )...2 C/W TO-263 (θ JC )...2 C/W MIC294A/2941A Input Supply oltage... 2 to +6 Operating Input Supply oltage... 2 to 26 Adjust Input oltage (Notes 9 and 1) to +26 Shutdown Input oltage....3 to +3 Error Comparator Output oltage....3 to +3 Across the full operating temperature, the minimum input voltage range for full output current is 4.3 to 26. Output will remain in-regulation at lower output voltages and low current loads down to an input of 2 at 25 C. Electrical Characteristics Limits in standard typeface are for T J = 25 C and limits in boldface apply over the full operating temperature range. Unless otherwise specified, IN = OUT + 1, I L = 1mA, C L = 1µF. The MIC2941A is programmed to output 5 and has SHUTDOWN.6. Symbol Parameter Condition Min Typ Max Units O Output oltage Accuracy 5 ma I L 1A % % % O T O O Output oltage Temperature Coefficient (Note 2) 2 1 ppm/ C Line Regulation I O = 1mA, ( OUT + 1) IN % Load Regulation I L = 5mA to 1.25A I L = 5mA to 1A (Note 3) IN O Dropout oltage (Note 4) I L = 5mA I L = 25mA I L = 1mA I L = 125mA I GND Ground Pin Current (Note 5) I L = 5mA I GNDDO Ground Pin Current at Dropout (Note 5) I L = 25mA I L = 1mA I L = 125mA IN =.5 less than designed OUT ( OUT 3.3) I L = 5mA % % ma ma ma ma ma 33 6 I LIMIT Current Limit OUT = (Note 6) A O P D e n Thermal Regulation (Note 7).5.2 %/W Output Noise oltage (1Hz to 1kHz) I L = 1mA C L = 1µF C L = 33µF 4 26 µ RMS µ RMS July 27 3 M

4 MIC294A/2941A Electrical Characteristics (MIC2941A Only) Parameter Condition Min Typ Max Units Reference oltage (Note 8) Adjust Pin Bias Current Reference oltage Temperature Coefficient 2 ppm/ C Adjust Pin Bias Current Temperature.1 na/ C Coefficient Shutdown Input Input Logic oltage Low (ON) High (OFF) 2. Shutdown Pin Input Current SHUTDOWN = SHUTDOWN = Regulator Output Current in Shutdown (Note 1) 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, T J(MAX), the junction-to-ambient thermal resistance, θ JA, and the ambient temperature, T A. The maximum allowable power dissipation at any ambient temperature is calculated using: P (MAX) = (T J(MAX) T A ) / θ JA. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. 2. Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. 3. 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. 4. Dropout oltage is defined as the input to output differential at which the output voltage drops 1 below its nominal value measured at 1 differential. At low values of programmed output voltage, the minimum input supply voltage of 4.3 over temperature must be taken into account. 5. 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. 6. The MIC294A features fold-back current limiting. The short circuit ( OUT = ) current limit is less than the maximum current with normal output voltage. 7. 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 2mA load pulse at IN = 2 (a 4W pulse) for T = 1ms. 8. REF OUT ( IN 1 ), 4.3 IN 26, 5mA < I L 1.25A, T J T J(MAX). 9. Circuit of Figure 3 with R1 15k Ω. SHUTDOWN 2 and IN 26, OUT =. 1. 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 6 must be of limited duration (< 1 ms) and duty cycle ( 1%). The maximum continuous supply voltage is na na July 27 4 M

5 MIC294A/2941A Typical Characteristics 5 Dropout oltage vs. Output Current 1 Dropout oltage 6 Dropout Characteristics DROPOUT OLTAGE () DROPOUT OLTAGE () I LOAD = 1.25A OUTPUT OLTAGE () I LOAD =5mA I LOAD = 1.25A OUTPUT CURRENT (A) INPUT OLTAGE () 4 vs. Output Current 4 vs. Supply oltage 5 vs. Supply oltage GROUND CURRENT (ma) A OUTPUT CURRENT (ma) GROUND CURRENT () FIXED 5 I LOAD =5mA SUPPLY OLTAGE () GROUND CURRENT (ma) FIXED 3.3 DEICE I LOAD =1.25A INPUT OLTAGE () GROUND CURRENT (ma) OUTPUT OLTAGE () I LOAD =5mA Fixed 3.3 Output oltage GROUND CURRENT (ma) CURRENT (A) I LOAD =1mA Short Circuit and Maximum Current OUT = NOMINAL OUT =.6.4 FIXED 3.3 ERSION.2 3SAMPLES GROUND CURRENT () GROUND CURRENT (ma) I LOAD =1.25A 1 I LOAD = 1mA vs. Input oltage R LOAD = INPUT OLTAGE () July 27 5 M

6 MIC294A/2941A Typical Characteristics (continued) ENABLE CURRENT () ADJUST PIN CURRENT (na) MIC2941/2 Shutdown Current EN =5 EN = MIC2942/3 Adjust Pin Current I LOAD =5mA OUTPUT (A) OUTPUT () Load Transient 75 5 C OUT =1µF mA TIME (ms) OUTPUT () INPUT () Line Transient C OUT =1µF TIME (ms) OUTPUT (A) OUTPUT () OUTPUT () INPUT () Load Transient 2 1 C OUT = 1 µf mA TIME (ms) Line Transient C OUT = 1 µf TIME (ms) OUTPUT IMPEDANCE ( ) Output Impedance vs. Frequency I LOAD = 1mA.1 1x1 1x1 1x1 1x1 3 1x1 3 1x1 3 FREQUENCY (Hz) 1x1 6 July 27 6 M

7 MIC294A/2941A Application Information External Capacitors A 1µF (or greater) capacitor is required between the MIC294A 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 3 C, so solid tantalums are recommended for operation below 25 C. The important parameters of the capacitor are an effective series resistance of about 5Ω or less and a resonant frequency above 5kHz. 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 3.3µF for current below 1mA or 2.2µF for currents below 1mA. Adjusting the MIC2941A to voltages below 5 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 1.23 output (Output shorted to Adjust) a 22µF (or greater) capacitor should be used. The MIC294A 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.22µF capacitor should be placed from the MIC294A input to ground if there is more than 1 inches of wire between the input and the AC filter capacitor or if a battery is used as the input. Programming the Output oltage (MIC2941A) The MIC2941A may be programmed for any output voltage between its reference and its 26 maximum rating. An external pair of resistors is required, as shown in Figure 3. OUT = REF x { 1 + R 1 /R 2 } I FB R 1 where REF is the nominal reference voltage and I FB is the Adjust pin bias current, nominally 2nA. The minimum recommended load current of 1 forces an upper limit of 1.2MΩ on the value of R 2, if the regulator must work with no load (a condition often found in CMOS in standby), I FB will produce a 2% typical error in OUT which may be eliminated at room temperature by trimming R 1. For better accuracy, choosing R 2 = 1kΩ reduces this error to.17% while increasing the resistor program current to 12. Since the MIC2941A typically draws 1 at no load with SHUTDOWN 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 1µF to 22µF only decreases the noise from 43µ to 16µ RMS for a 1kHz bandwidth at 5 output. Noise can be reduced by a factor of four with the MIC2941A by adding a bypass capacitor across R 1. Pick 1 CBYPASS 2πR 12Hz or about.1µf. When doing this, the output capacitor must be increased to 22µF to maintain stability. These changes reduce the output noise from 43µ to 1µ RMS for a 1kHz bandwidth at 5 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 MIC294A 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 (4 at light loads), and very low quiescent currents (24 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 2 below ground), and load dump (positive transients up to 6) conditions. A wide operating temperature range with low temperature coefficients is yet another reason to use these versatile regulators in automotive designs. OUTPUT OLTAGE ERROR INPUT OLTAGE NOT * ALID Figure 1. ERROR Output Timing NOT * ALID July 27 7 M

8 MIC294A/2941A Typical Applications IN + IN +IN OUT OUT = 5 IN OUT OUT GND + 1µF ON SHUTDOWN INPUT OFF SHUTDOWN GND ADJUST 1.23 R1 1 pf 22µF OUT = REF x (1 + R1 ) R 2 REF R2 Figure 2. MIC294A-5. Fixed +5 Regulator Figure 3. MIC2941A Adjustable Regulator + IN +5 to +7 IN OUT OUT =IN SHUTDOWN INPUT ON OFF SHUTDOWN GND + IN OUT ADJ 1pF 3k 1% + CC OUT 1µF GND ADJUST k 22k 1% 2N k 1% * Minimum Input-Output oltage Ranges from 4 to 4, depending on Load Current. Figure 4. MIC2941A Wide Input oltage Range Current Limit Adjust Pin Low = Enable Output. Q1 ON = 3.3, Q1 OFF = 5.. Figure 5. MIC2941A 5. or 3.3 Selectable Regulator with Shutdown July 27 8 M

9 MIC294A/2941A Package Information 3-Pin TO-22 (T) 3-Pin TO-263 (U) July 27 9 M

10 MIC294A/2941A 5-Pin TO-22 (T) 5-Pin TO-263 (U) July 27 1 M

11 MIC294A/2941A MICREL, INC. 218 FORTUNE DRIE SAN JOSE, CA USA TEL +1 (48) FAX +1 (48) WEB 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. 24 Micrel, Incorporated. July M