MIC2940A and MIC2941A 1.25A Low Drop Out Voltage Regulator al Preliminary InformationProduction Q1 '94 Generali Description Features The MIC2940A and MIC2941A are "bulletproof" efficient * High output voltage accuracy voltage regulators with very low dropout voltage (typically * Guaranteed 1.2A output 40mV at light loads and 280mV at 1A), andverylowquiescent * Ow quiescent current current (Q0uA typical). The quiescent current ofthe MIC29404 Low dropout voltage ; ; increases only slightly in dropout, thus prolonging battery life. Extremely tight load and line regulation Key MIC2940A features include protection against reversed Very low temperature coefficient battery, fold-back current limiting, andautomotive loaddump" * Current and thermal limiting protection (60V positive transient). . met ean wanstand -20V reverse battery and +60V The MIC2940 is available in both fixed voltage and adjustable, Logic-controlled slactronic shutdown voltage configurations. The MIC2940A-xx devices are three, Output programmable from 1.24V to 26V(MIC2941A) pin fixed voltage regulators. A logic-compatible shutdown, Available in TO-220 10-263 TO-220-5, TO-263-5 input is provided on the adjustable MIC2941A, which enables TO-3. and TO-3-4 packages , , the regulator to be switched on and off. 7 ae Applications * Battery Powered Equipment * Cellular Telephones * Laptop, Notebook, and Palmtop Computers * PCMCIA V,,. and V,, Regulation/Switching Bar Code Scanners * Automotive Electronics SMPS Post-Regulator/ DC to DC Modules Pin Configuration * Voltage Reference High Efficiency Linear Power Supplies mH Output O ) Case is Ground ee on O O TO-3 Package (MIC2940A-xxBK) Output Adjust i Hl i INPUT GROUND OUTPUT TO-263 Package hutdown = (Mmi2940A-xxBU) Input Case is ground i TO-3-5 Package (MIC2941 ABK) MIC2941A Pinout ttt 1) Adjust 2) Shutdown 3) Ground 12345 4) Input TO-263-5 Package 5) Output (MIC2941 ABU) So Qo Cae Oo CS 12 3 1 INPUT GROUND OUTPUT TO-220 Package (MIC2940A-xxBT) Tab is Ground on TO-220 and TO-263 packages TO-220-5 Package (MiC2941 ABT) 6-45MIC2940A/2941A Micrel Ordering Information Absolute Maximum Ratings . If Military/Aerospace specified devices Part Number Voltage | Temperature Range Package are required, contact your local Micrel MIC2940A-3.3BK 3.3 -40C to +125C TO-3 representative/distributor for availability and specifications. MIC2940A-3.3BT 3.3 40C to +125C TOQ-220 P og _ Power Dissipation (Note 1) Internally Limited MIC2940A-3.3BU 3.3 40C to +125C TO-263 Lead Temperature (Soldering, 5 seconds) 260C } Storage Temperature Range -65C to +150C MIC2940A-5.0BK 5.0 40C to +125C TO-3 Operating Junction Temperature Range - _Ag . 40C to +125C MIC2940A-5.0BT 5.0 40C to +125C TO-220 Input Supply Voltage 20V to +60 MIG2940A-5.0BU 5.0 40C to +125C TO-263 | Operating Input Supply Voltage 2V" to 26V Adjust Input Voitage (Notes 9 and 10) MIC2940A-12BK 12 40C to +125C TO-3 -1.5V to +26V Shutdown Input Voltage 0.3V to +30V MIC2940A-12BT 12 40C to +125C TO-220 Error Comparator Output Voltage -0.3V to +30V ESD Rating >+2000V MIC2940A-12BU 12 40C to +125C TO-263 MIC2941ABK Adj 40C to +125C TO-3-4 + Across the full operating temperature, the minimum : input voltage range for full output current is 4.3V to 26V. MIC2941ABT Adj 40C to +125C T0-220-5 Output will remain in-regulation at lower output voltages MIC2941ABU Adj -40C to +125C TO-263-5 and low current loads down to an input of 2V at 25C. Schematic Diagram * Junction temperatures Rg 27 BK R21 8Q Ri R22 Ros 23 60 ka 150 koa 50 ki DENOTES CONNECTION ON FIXED VOLTAGE VERSIONS ONLY 6-46MIC2940A/2941A Electrical Characteristics Micrel 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_ = 10.F. The MIC2941A is programmed to output 5V and has Veumpown 0-6V. Symbol Parameter Conditions Min Typical Max Units Vo Output Voltage 4.950 5.00 5.050 Vv (5.0 or adjustable 4.900 5.100 versions) SmA<I <1A 4.880 5.00 5.120 Output Voltage Variation from designed V,,,,, -1 1 % Accuracy -2 2 5mAsI <1A -2.5 2.5 AV, Output Voltage (Note 2) 20 100 | ppm/C AT Temperature Coef. AV, Line Regulation Vin = Vour + 1V to 26V 0.03 0.10 % Vo 0.40 AV Load Regulation |. =5mA to 1A 0.04 0.16 % Vo 0.20 (Note 3) Vin Vo Dropout Voltage I, =5mA 60 100 mV (Note 4) 150 | = 250mA 150 200 320 |, = 1000mA 280 450 600 | = 1250mA 300 END Ground Pin Current] |, = 5mA 90 150 pA (Note 5) 180 |, = 250mA 3 45 mA 6 |, = 1000mA 22 35 45 | = 1250mA 35 I gwopo Ground Pin Vy = 0.5V less than designed V,,,, 180 300 LA Current at Dropout | (V,,,, 2 3.3V) (Note 5) _ Vs ear Current Limit Vour = OV 1.6 2 A (Note 6) 2.4 AV, Thermal Regulation} (Note 7) 0.05 0.2 %IW AP, e, Output Noise C, = 10uF 400 uv RMS Voltage (10Hz to 100kHz) | C, = 33yF 260 I, = 100mA 6-47MIC2940A/2941A Micrel Electrical Characteristics (mic2941a Only) Parameter Conditions Min | Typical; Max Units Reference Voltage 1.210 1.235 1.260 Vv 1.200 1.270 V max Reference Voltage (Note 9) 1.185 1.285 Vv Adjust Pin 20 40 nA Bias Current 60 Reference Voltage (Note 8) 20 ppm/c Temperature Coefficient Adjust Pin Bias Ou nA?C Current Temperature Coefficient Shutdown Input Input Logic Voitage 1.3 Vv Low (ON) 0.7 High (OFF) 2.0 Shutdown Pin VeHuTDOWN =2.4V 30 50 HA Input Current 100 Venutbown = 30 450 600 uA 750 Regulator Output (Note 11) 3 10 HA Current in Shutdown 20 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, 8,,, and the ambient temperature, T,. The maximum allowable power dissipation at any ambient temperature is calculated using: Py. = (Tmax )/ 98, 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 Voitage 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. 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 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 V,, = 20V (a 4W pulse) for T = 10ms. Note 8: Vie. S Vou S (Vy 1: Vd, 4.3V 5 Vi, S$ 26V, SMA <1 < 1.25A, TS Ty ayy, Note 9: Comparator thresholds are expressed in terms of a voltage differential at the Adjust 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 = Vay, Vper = (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 95 mV x5V/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: Circuit of Figure 3 with R12 150kQ. Vonutpown 22 and Vy. $ 26 V,Vou, = 0. 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 26V. our = OV) current limit is less than the maximum current 6-48MIC2940A/2941A Micrel Typical Characteristics Ground Pin Current Ground Pin Current Ground Pin Current vs. Input Voltage vs. Temperature vs, Load _ 250 1 EB < = Z = 200 5 4 a Zz uu a Ww oc D> a a gS 150 3 a eo z 6 z a Z Gq 100 IL=5 8 3 2 L 5 0. 6 3 & S 50 S 00 0412 3 45 67 8 -75-50-25 0 25 50 75 100 125 150 o 1 10 100 1000 INPUT VOLTAGE (V) TEMPERATURE (C) OUTPUT CURRENT (mA) Ground Pin Current Ground Pin Current vs. Input Voltage vs. Temperature Output Noise Voltage 40 36 < ~ 32 ~ IL =1.25A 2 i 28 a 3s c oc = 24 x i) 5 Ww Go 20 a 8 = 16 2 5 a o = 9g 12 9 g a (, = 100 Ww 3 f 3 : g ViIN= ac = S g s Vout 012 345 67 8 -75 -50-25 0 25 50 75 100125 150 0.1 1 10 100 1000 INPUT VOLTAGE (V) JUNCTION TEMPERATURE (C) LOAD CURRENT (mA) Ripple Rejection Ripple Rejection vs. Frequency at vs. Frequency 0 Medium Current at High Current 100 Output Impedance = oon E VIN =8 a a = a . Vout = z = L ~ "| Coc Cop = 10uF Zz Zz Ww E = a 3 9 ate f + = i 2 , ont i Oo o 4 4 uty Lu Ww i a we IL =1A a E oa c = T Aa t uy Vin =6V uy Vin = 6V Bot te in o VOUT = x Vout = o L=250m or = ec = Ya ig SL = 10uF "ps1 CL = 10uF 3 Att te 1 | 0.01 0.4 1 10 100 1000 01.01 1 10 100 1000 0.01 OT O4 4 10. 400 1000 FREQUENCY (kHz) FREQUENCY (kHz) FREQUENCY (kHz) Line Transient Response Line Transient Response 6 CL= 1OnE & ez 400 I= 10ma az eit Your = eit Sh 0 so FZ fZ =P az or ox 5G -400 56 5 3 Wu lu LO 8Vv EO Dt Dt ae ae 25 ev =O > > 0 02 04 06 O08 1 0 1 2 3044 5 TIME (mS) TIME (mS) 6-49MIC2940A/2941A Micrel Typical Characteristics, Continued Load Transient Response Load Transient Characteristics 800 3 Vin = 6V oo 200 VIN = 6 FE 400 Vout = FE 100 Vout = Ss Qu 0 Qu = So 9 0 w ke bz g 4 z= -400 at < is ER 100 a 3 3 2 9 -800 -200 b kb b > 2 Pr 250mA Pr 250mA 5 ; 35 TO0HA 35 1OOUA 0 0 10 20 30 40 0 10 20 30 40 50 60 01 2 3 4 5 6 TIME (mS) TIME (mS) INPUT VOLTAGE (VOLTS) Short-Circuit Output Current and Maximum 10 Enable Transient Enable Transient Output Current 3 = = = CURRENT Sw 6 (CE Su Vout = 5 ag ao Ea Et & Bu 4 a4 i 3 25 cc > > x 2 3 ge Ze 5 Ww 2 Ww a ag Bg 5 CURRENT 5h 545 Vout =0 Io LO 1.0 as o 4 2 3 4 ~5 o> 0 o4 2 304 ~5 -75-50-25 0 25 5075 100125150 TIME (mS) TIME (mS) JUNCTION TEMPERATURE (C) wW Fold-B: urrent Limiti Drapo! o Thermal 200 old-Back Current Limiting 5.5 Drop: ut Re 1 = a Ow 1 = 2 SO 9. cz 5 175 wW 2 g f FO o = 0. 3 6 2 1.50 oo S = 5 i] 2 9 = a | 9 az 5 125 5 we 3 fr 01 se a On 15 1.00 @ 0 10 2 30 40 oo 2 3 04 5 0 02 04 06 08 1.0 1.2 TIME (mS) OUTPUT VOLTAGE (V) OUTPUT CURRENT (A) 6-50MIC2940A/2941A Micrel 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 about30C, so solid tantalums are recommended for operation below -25C. The important parameters of the capacitor are an effective series resistance of about 52 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 10 mA. Adjusting the MIC2941A/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 Adjust) 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 MIC2941A 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 MIC2941A Adjust terminal 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 Adjust and increasing the output capacitor to at least 22\F will remedy this. Programming the Output Voltage (MIC2941A/ MIC29403) 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. The complete equation for the output voltage is Vour = Veer X{14+R/Re} +, R, where V,,_. is the nominal 1.235 reference voltage and I, is the Adjust pin bias current, nominally 20nA. The minimum recommended load current of 1 A 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 R, = 100k reduces this error to 0.17% while increasing the resistor program current to 12 uA. Since the MIC2941A typically draws 100 1A at noload with SHUTDOWN 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 capacitor. This is relatively inefficient, as increasing the capacitor from 1 uF to 220 LF only decreases the noise from 430uV to 160UV,,,, 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 R,, since it reduces the high frequency gain from 4 to unity. Pick Cevpass = 1___ 27Ri 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 nV rms for a 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. 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 (90uA 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 NOT* ERROR Valin VALID INPUT oN VOLTAGE BV 1.3V * SEE APPLICATIONS INFORMATION Figure 1. ERROR Output Timing 6-51MIC2940A/2941A Micrel Typical Applications +VIN VIN | | ViN VOUT +ViN Vout 1.2V 26V Vv OUT _ Vour= Vv SHUTDOWN | | NPUT | SHUTDOWN 10uF + Ry] .01 F OFF 10uF f GND ADJUST H ON GND | L 1.23V L t - = = VREF j Ra Vout = VREFX (1+ -, ) 1 Figure 2. MIC2940A-5.0 Fixed +5V Regulator Figure 3. MIC2941A Adjustable Regulator +5V to +7V +VIN +Vin Veoc OUT VIN y VOUT = VIN SHUTDOWN VOUT OUTHKR--___ INPUT SHUTDOWN OFF + on _[- 300kQ + 10HF GND ADJUST 1% GND ADJUST | L 4 L , 180k 5v 470 kQ 1% L 1% av So \ 2N2222 Input Output oO 33V 1 5.0V *MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mvV, ADJUST PIN LOW= ENABLE OUTPUT. Q1 ON = 3.3V, Q1 OFF =5.0V. DEPENDING ON LOAD CURRENT. Figure 4. MIC2941A Wide Input Voitage Range Current Limiter Figure 5. MIC2941A 5.0V or 3.3V Selectable Regulator with Shutdown. 6-52