ie! MIC2940A,29401 ,29403,2941A 1.25A Low Drop Out Voltage Regulator Preliminary Information al General Description The MIC2940A family are "bulletproof" efficient voltage regulators with very low dropout voltage (typically 40mV at light loads and 280mvV at 1A), and very low quiescent current (90uA 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 MIC2840 is available in several configurations. The MIC2940A-xx devices are three pin fixed voltage regulators. The MiC29401 is a fixed regulator offering logic compatible ON/OFF switching input and an error flag output. This flag may also be used as a power-on reset signal. A logic- compatible shutdown input is provided on the adjustable MIC29414, which enables the regulator to be switched on and off. The MIC29403 is a five pin adjustable version that includes an error flag output that warns of alow output voltage. which is often due to failing batteries on the input. Pin Configuration Features High output voltage accuracy Guaranteed 1.2A output Low quiescent current Low dropout voltage Extremely tight load and line regulation Very low temperature coefficient Current and thermal limiting linput can withstand -20V reverse battery and +60V positive transients e Error flag warns of output dropout e Logic-controlied electronic shutdown Qutput programmable from 1.24V to 29V(MIC2941A/ MIC29403) Available in TO-220, TO-263, TO-220-5, TO-263-5, TO-3, and TO-3-4 packages. Applications Battery Powered Equipment Cellular Telephones e Laptop, Notebook, and Palmtop Computers PCMCIA V,,, and V_, Regulation/Switching e Bar Code Scanners Automotive Electronics Output SMPS Post-Regulator/ DC to DC Modules Voltage Reference O ) Case is Ground High Efficiency Linear Power Supplies Input a TO-3 Package C) OC) (MIC2940A-xxBK) Output Pin 2 : 0 D . INPUT GROUND OUTPUT Pin 3 TO-263 Package Input Case is ground = (MIC2940A-xxBU) Pin2 Pin3 MIC29401 Error ON MIC29403 Error FB MIC2941A FB ON TO-3-5 Package (MIC29401/29403/2941ABK) 12 3 12346 Five Lead Package Pin Functions: INPUT GROUND OUTPUT TO-220 Package (MIC 2940A-xxBT) TO-220-5 Package (MIC29401/2941 A/29403BT) MIC29401 MIC2941A MIC29403 1) Error FB Error 2) ON ON FB 3) Ground Ground Ground 12345 4) Input Input Input TO-263-5 Package 5) Output Output Output (MIC29401/2941 A/29403BU) 6-42MIC2940A/2940 1/294 1A/29403 Ordering Information Part Number Voltage | Temperature Range | Package MIC2940A-3.3BK 3.3 40C to +125C TO-3 MIC2940A-3.3BT 3.3 40C to +125C TO-220 MIC2940A-3.3BU 3.3 40C to +125C TO-263 MIC2940A-4.8BK 4.8 40C to +125C TO-3 MIC2940A-4.8BT 48 40C to +125C TO-220 MIC2940A-4.8BU 4.8 40C to +125C TO-263 MiC2940A-5.0BK 5.0 40C to +125C TO-3 MIC2940A-5.0BT 5.0 40C to +125C TO-220 MIC2940A-5.0BU 5.0 40C to +125C TO-263 MIC2940A-15BK 15 40C to +125C TO-3 MiC2940A-15BT 15 40C to +125C TO-220 MIC2940A-15BU 15 40C to +125C TO-263 MIC29401-3.3BT 3.3 40C to +125C TO-220-5 MIC29401-3.3BU 3.3 40C to +125C TO-263-5 MIC29401-4.8BT 4.8 40C to +125C TO-220-5 MIC29401-4.8BU 4.8 40C to +125C TO-263-5 MIC29401-5.0BT 5.0 40C to +125C TO-220-5 MiC29401-5.0BU 5.0 40C to +125C TO-263-5 MIC29401-15BT 15 40C to +125C TO-220-5 MiC29401-15BU 15 40C to +125C TO-263-5 MIC29403BK Adj 40C to +125C TO-3-4 MIC29403BT Adj 40C to +125C TO-220-5 MIC29403BU Adj 40C to +125C TO-263-5 MIC2941ABK Adj 40C to +125C TO-3-4 MIC2941ABT Adj 40C to +125C TO-220-5 MIC2941ABU Adj 40C to +125C TO-263-5 * Junction temperatures Micrel 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 seconds) 260C Storage Temperature Range -65C to +150C Operating Junction Temperature Range 40C to -125C Input Supply Voltage -20V to +60V Feedback 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 ESD Rating >+2000V 6-43MIC2940A/2940 1/294 1A/29403 Micrel Electrical Characteristics Limits in standard typeface are for T, = 25C and limits in boldface apply over the full operating temperature range. Unless otherwise specified, V,. = V,,, + 1V, |, = 1000mA, C= 2.2uF. The MIC2941A and MIC29403 Feedback pins are tied to the 5V Tap, Output is tied to Output Sense (V,,,, = 5V). and Va roown 0.6V. Symbol Parameter Conditions Typical Min Max Units Vo Output Voltage 5.0 4.950 5.050 Vv (5.0 or adjustable 4.900 5.100 versions) 5mA<I <1A 5.0 4.880 5.120 Output Voltage Variation from designed V,,,,, -1 1 % Accuracy 2 2 5mA<|,<1A -2.5 2.5 AV Output Voltage (Note 2) 20 100 | ppm/C AT Temperature Coef. AV, Line Regulation in = BV to 26V 0.03 0.10 % Vo. 0.40 AVo Load Regulation |. =5mA to 1A 0.04 0.16 % Vo 0.20 (Note 3) Vin7 Vo Dropout Voitage 1 =5mA 60 100 mV (Note 4) 150 | = 250mA 150 200 320 |, = 1000mA 280 450 600 | = 1250mA 300 leno Ground Pin Current] |, = 5mA 90 150 BA (Note 5) 180 |, = 250mA 3 45 mA 6 |, = 1000mA 22 36 45 |, = 1250mA 35 lenooo Ground Pin Vy = 0.5 less than designed V,,_, 180 300 BA Current at Dropout (Note 5) Vr Current Limit Vour = OV 1.6 2 A {Note 6} 2.4 AV, Thermal Regulation | (Note 7) 0.05 0.2 SofW AP, e, Output Noise C, = 10uF 400 uV RMS Voltage (10Hz to 100kHz) | C, = 33uF 260 | = 100mA 6-44MIC2940A/2940 1/294 1A/29403 Micrel Electrical Characteristics (Continued) MIC29403/MIC2941A Parameter Conditions Typ. Min Max Units Reference Voltage 1.235 1.210 1.260 Vv 1.200 1.270 V max Reference Voltage (Note 9) 1.185 1.285 Vv Feedback Pin 20 40 nA Bias Current 60 Reference Voitage (Note 8) 20 ppm/c Temperature Coefficient Feedback Pin Bias 0.1 nAkC Current Temperature Coefficient Error Comparator MIC29401/MIC29403 Output Leakage Von = 30V 0.01 1.00 LA Current 2.00 Output Low Vin = 4.5V 150 250 mv Voltage lo, = 250A 400 Upper Threshold (Note 10) 60 40 mV Voltage 25 Lower Threshold (Note 10) 75 95 mV Voltage 140 Hysteresis (Note 10) 15 mV Shutdown input MiC29401/MIC29402 Input Logic Voltage 1.3 v Low (ON) 0.7 High (OFF) 2.0 Shutdown Pin Vonutoown = 2-4 30 50 HA Input Current 100 Venutbown = SOV 450 600 LA 750 Regulator Output (Note 11) 3 10 HA Current in Shutdown 20 6-45MIC2940A/2940 1/294 1A/29403 Micrel Note 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_,,,,,,. the junction-to-ambient thermal resistance, Q,,. and the ambient temperature, T,. The maximum allowable power dissipation at any ambient temperature is calculated using: P 4.4, = (Tyayev,- T4)/Q,, Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. Note 2: Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range. Note 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. Note 4: 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 (2.3 V over temperature) must be taken into account. Note 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. Note 6: The MIC2940A features fold-back current limiting. The short circuit (V with normal output voltage. Note 7: Thermal regulation is defined as the change in output voltage ata time T after a change in power dissipation is applied, excluding load or line regulation effects. Specifications are for a 200mA load pulse at V,, = 20V (a 4W pulse) for T = 10mS. Note 8 Vane Vouy S (Vay 1 Vd. 2.3 SV, 5 30V, SMA <1 < 1.254, TS Tyas Note 9: Comparator thresholds are expressed in terms of a voltage differential at the Feedback terminal below the nominal reference voltage measured at 6V input. To express these thresholds in terms of output voltage change. multiply by the error amplifier gain = V_,, Nocp = (R1 + R2\R2. For example, at a programmed output voltage of SV. the Error output is guaranteed ta go low when the output drops by 95 mV x 5V/1.235 V = 384 mV. 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. Note 10: Van urpown 22 Ve Vin $30 ViVouy = 0, with Feedback pin tied to 5V Tap. Note 11: 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. Note 12: Maximum positive supply voltage of 60 V must be of limited duration (< 100 mS) and duty cycle (< 1%}. The maximum continuous supply voltage is 30 V. our = OV) current limit is less than the maximum current Schematic Diagram Rai ou Aza 60 Kha Aa Soaty 6-46MIC2940A/2940 1/294 14/29403 Typical Characteristics Ground Pin Current vs. {nput Voltage 10 Ground Pin Current vs. Temperature 250 Micrel Ground Pin Current vs. Load s Z z KE g = z > Z = 200 5 a 2 3 x > 5 150 3 a 2 z a z oo z Gg 100 8 8 5 - 3 So 6 & 50 9 041423 45 67 8 -75-50 -25 0 25 50 75 100 125150 0.1 1 10 100 1000 INPUT VOLTAGE (V} TEMPERATURE (C) OUTPUT CURRENT imA) Ground Pin Current Ground Pin Current vs. Input Voitage vs. Temperature Output Noise Voltage 0 z ~ E C= & > 1p =125A a Ee 2 E # # = oc rc = a) 3 lu 3 38 9g Z 2 A a 3 3 ! I, = 100 uw low 3 3 g VIN = 6V ac = 6 g S Vout 0123 45 6 7 8 -75 -50-25 0 25 50 75 100125 150 ot 1 10 106 1000 INPUT VOLTAGE (V) JUNCTION TEMPERATURE ['C) LOAD CURRENT ima) Rippie Rejection Ripple Rejection vs. Frequency at vs. Frequency < Medium Current at High Current 100 Output Impedance _ = _ 1 L= 100p = * _ a a + = = Vout =5 g g cs 2 4 Coon ae Zz Zz iva 9 g o 3 = ff wi Ww w w w iL =tA ia = a wy 2 T= 16y Tei a Vin =6V Z Vin = 6V bor t a Vout = & cout = = [=250m: = = 10uF- = 19,F 2 5 CL = 10uF "pet baie 5 - 20 1 oo, Lh msl O01 Gt 1 1G 100 1000 ot ot 1 10 100 61000 0.01 01 1 10 100 1000 FREQUENCY [kHz) FREQUENCY (kHz Line Transient Response cl= 1p = 10mA v 400 CHANGE (mv) -400 OUTPUT VOLTAGE CHANGE (mV) 8v INPUT OUTPUT VOLTAGE INPUT VOLTAGE VOLTAGE 6V 6 0.2 04 G6 O08 1 0 1 TIME (mS) FREQUENCY (kHz} Line Transient Response CL= 1) = 10mA Vout = 2 3 4 5 TIME (mi 6-47MIC29404/2940 1/294 1A/29403 Micrel Typical Characteristics, Continued Load Transient Response " Load Transient Characteristics w 801 w es vine go vin 6 KE 400 Vout = EE 100 Vout = = on ou = 3 23 2S 0 ww b2 b2 go 4 pe at 4 ay -400 Sr 100 5 56 : 56 o 3 9 -800 -200 2 E bE z 2 om 0m4 QG 250ma 5 x x 3 ag 100UA 38 100yA o 10 20 30 40 0 10 20 30 49 50 60 0 1 > 3 4 5 6 TIME (mS) TIME imSi INPUT VOLTAGE (VOLTS) Short-Circuit Output Current and Maximum 19 Enable Transient Enable Transient 20 Output Current eo 8 eo S = C=! < CURRENT Sug [SL Su - '* OUT = ag ag _ Ea re kK ls 4 at 531 8 98 tc > > ce 2 3 14 z= zs kb so su z 2 ou 12 ee) ag 5 [A guneent 56 o Bs Your = zo LO 1.0 oS 0 1 2 304 5 aS oo4 2 3 4 5 -75-50 -25 0 25 5075 100125150 TIME imS} TIME (mS} JUNCTION TEMPERATURE (:C} 6 Thermal 2.00 Fold-Back Current Limiting Dropout Q . Be 1 = Ss Ow < 2 7s 5 1.75 W as iw < zs 5 > 5 o 35 3 1.50 Le Le S > 2 < 2 ao 8 az 5S 1.25 CS wo 3 & Ske oa of a5 100 a 0 10 20 30 40 o 1 2 3 4 5 0 02 04 06 08 10 12 a TIME (mS) OUTPUT VOLTAGE (V7) OUTPUT CURRENT (A) 6-48MIC2940A/2940 1/294 1A/29403 Applications Information External Capacitors A 10uF (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, sosolidtantalums are recommended for operation below ~25C. The important parameters of the capacitor are an effective series resistance of about 5Q 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 3.3uF for current below 100mA or 2.2uF for currents below 10mA. Adjusting the MIC2941 A/29403 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 Feedback) a 22uF (or greater) capacitor should be used. The MIC2940A will remain stable and in regulation with no load in addition to the internal voltage divider, unlike many other voltage regulators. This is especially important in CMOS RAM keep-alive applications. When setting the output voltage of the MIC2941 A/29403 version with external resistors, a minimum load of 1mA is recommended. A 0.22uF 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. Stray capacitance to the MIC2941 A/29403 Feedback terminal (pin 7) can cause instability. This may especially be a problem when using high value external resistors to set the output voltage. Adding a 100pF capacitor between Output and Feedback and increasing the output capacitor to at least 22uF will remedy this. Error Detection Comparator Output (MIC29401/ 2941 A/MIC29403) A logiclow output will be produced by the comparator whenever the MIC29401/2941A/29403 output falls out of regulation by more than approximately 5%. This figure is the comparator's built-in offset of about 6OmV 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 MIC29401/2941 A/29403. For example, the error flag trip level is typically 4.75V for a 5V output or 11.4V for a 12V 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 ERROR signal and the regulated output voltage as the MiC29401/2941 A/29403 input is ramped up and down. The ERROR signal becomes valid (low) at about 1.3V input. It goes high at about 5V input (the input voltage at which V,.,- = 4,75). Since the MIC29401/ Micrel 2941A/29403's dropout voltage is load-dependent (see curve in Typical Performance 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. 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 1MQ. The resistor is not required if this output is unused. in shutdown mode, ERROR will go high if it has been pulled up to_an external supply. To avoid this invalid response. ERROR should be pulled up to V Out Programming the Output Voltage (MIC2941A/ MIC29403) The MIC2941A/29403 may be pin-strapped for 5V using its internal voltage divider by tying Pin 1 (output) to Pin 2 (sense) and Pin 7 (feedback) to Pin 6 (V 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 Vour = Vege X(1+A Ro} +1, A, where V,,_,. is the nominal 1.235 reference voltage and I_, is the feedback pin bias current, nominally 20nA. The minimum recommended load current of 1 uA forces an upper limit of 1.2MQ on the value of R,,, if the regulator must work with no load (a condition often found in CMOS in standby), I... will produce a 2% typical error in V_,,,, which may be eliminated at room temperature by trimming R,. For better accuracy, choosing A, = 100k reduces this error to 0.17% while increasing the resistor program current to 12 uA. Since the MIC2941 A/29403 typically draws 100 LA at no load with Pin 2 open-circuited, 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 4,75V, OUTPUT | | VOLTAGE | | ERROR NOT NOT * ERROR VALID LI H VALID | | INPUT VOLTAGE * SEE APPLICATIONS INFORMATION Figure 1. ERROR Output Timing 6-49MIC2940A/2940 1/294 1A/29403 capacitor. This is relatively inefficient, as increasing the capacitor from 1 uF to 220 uF only decreases the noise from 430uV to 160uV,,,, for a 100KHz bandwidth at 5V output. Noise can be reduced fourfold by a bypass capacitor across R,,, since it reduces the high frequency gain from 4 to unity. Pick Caypass = ---1__.- 2mRr 200 Hz or about 0.01 uF. When doing this, the output capacitor must be increased to 22 uF to maintain stability. These changes reduce the output noise from 430 pV to 100 pV rms fora 100 kHz 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. Micrel! 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 toads), and very low quiescent currents (9OUA 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. Typical Applications Vout ry Vour = 5V + 2.2uF GND | ~ ! Figure 2. MiC2940A-5.0 Fixed +5V Regulator +VIN +ViIN __ * =V ERROR ERROR VouTL YOUT=VIN SHUTDOWN _| INPUT SD OFF ON _f S z oO an 3 MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mvV. DEPENDING ON LOAD CURRENT Figure 4. MIC2941A/29403 Wide Input Voitage Range Current Limiter +V IN Vout y REF au 100kQ K+) VIN VouT ERROR ERROR yj 1.2 30V OUTPUT OUT | | SHUTDOWN __| <1, 233uF INPUT OFF Ry4].01 _f- GND FB uF ON t 1.23V 4 a VREF oR 2 t = NOTE: PINS 2 AND 6 ARE LEFT OPEN SEE APPLICATIONS INFORMATION Figure 3. MIC2941A/29403 Adjustable Regulator +7V +ViIN Voc OUT SHUTDOWN | PUT gh fT ov + ON 300kQ =p 3.3pF GND 1% PIN 3 LOW= ENABLE OUTPUT. Q1 ON = 3.3V. Q1 OFF = 5.0V. Figure 5. MIC2941A/29403 5.0V or 3.3V Selectable Regulator with Shutdown. 6-50