a a | je MIC2937A,29371 ,29372,29373 I alle! Cr 750mA Low Drop Out Voltage Regulator ~ ~ Preliminary Information General Description Features High output voltage accuracy Guaranteed 750mA 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 output dropout * Logic-controlled electronic shutdown * Output programmable from 1.24V to 29V(MIC29372/ MiC29373) The MIC2937A family are "bulletproof" efficient voltage regulators with very low dropout voltage (typically 40mvV at light loads and 300mV at 500mA), and very low quiescent current (Q0uA typical). The quiescent current of the MIC2937A increases only slightly in dropout, thus prolonging battery life. Key MIC2937A features include protection against reversed battery, fold-back current limiting, and automotive "load dump" protection (60V positive transient). The MIG2937 is available in several configurations. The MiC2937A-xx devices are three pin fixed voltage regulators. The MIC29371 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- =, Available in TO-220, TO-263, TO-220-5, TO-263-5, compatible shutdown input is provided on the adjustable and SOT-223 packages. MIC29372, which enables the regulator to be switched on and : . off. The MIC29373 is a five pin adjustable version that Applications includes an error flag output that warns of a low output voltage, Battery Powered Equipment which is often due to failing batteries on the input. An eight Cellular Telephones pin DIP and SOIC adjustable version of the MIC29372 is Laptop, Notebook, ard Palmtop Computers available that includes both shutdown and error flag pins, and SCSI Il Active Terminators may be pin-strapped for 5V output, or programmed from 1.24 PCMCIA V.,. and V,,, Regulation/Switching V to 29 V with the use of two external resistors. Bar Code Scanners Automotive Electronics SMPS Post-Regulator/ DC to DC Modules High Efficiency Linear Power Supplies Pin Configuration nt 5 5 TEE aay SOT-223 Package (MIC2937A-xxBST) INPUT GROUND OUTPUT TO-263 Package (MIC2937A-xxBU) OO Five Lead Package Pin Functions: Mic29371 MIC29372 MIC29373 1) Error FB Error 12 3 12345 2) ON ON FB _ 3) Ground Ground Ground INPUT GROUND OUTPUT 4) Input Input Input TO-220 Package TO-220-5 Package 5) Output Output Output + a4 (MIC2937A-xxBT) | (MIC 29371/29372/29373BT) TO-263-5 Package (MIC29371/29372/29373BU) 6-33MIC2937A/2937 1129372129373 Ordering Information Part Number Voltage | Temperature Range* | Package MIC2937A-2.8BS 2.85 40C to +125C SOT-223 MIC2937A-2.8BT 2.85 40C to +125C TO-220 MIC2937A-3.3BS 3.3 40C to +125C SOT-223 MIC2937A-3.3BT 3.3 40C to +125C TO-220 MIC2937A-4.8BS 4.8 40C to +125C SOT-223 MIC2937A-4.8BT 48 40C to +125C TO-220 MiC2937A-5.0BS 5.0 40C to +125C SOT-223 MIC2937A-5.0BT 5.0 40C to +125C TO-220 MIC2937A-12BS 12 40C to +125C SOT-223 MIC2937A-12BT 12 40C to +125C TO-220 MIC2937A-15BS 15 40C to +125C SOT-223 MIC2937A-15BT 15 40C to +125C TO-220 MIC2937 1-2.8BU 2.85 40C to +125C TO-263-5 MIC29371-2.8BU 2.85 40C to +125C TO-263-5 MIC29371-3.3BT 3.3 40C to +125C TO-220-5 MIC29371-3.3BU 3.3 40C to +125C TO-263-5 MIC29371-4.8BT 48 40C to +125C TO-220-5 MIC29371-4.8BU 48 40C to +125C TO-263-5 MIC29371-5.0BT 5.0 40C to +125C TOQ-220-5 MIC29371-5.0BU 5.0 40C to +125C TO-263-5 MIC29371-12BT 12 40C to +125C TO-220-5 MIC29371-12BU 12 40C to +125C TO-263-5 MIC29371-15BT 15 40C to +125C TO-220-5 MIC29371-15BU 15 40C to +125C TO-263-5 MIC29372BT Adj 40C to +125C TO-220-5 MIC29372BU Adj 40C to +125C TO-263-5 MIC29373BT Adj 40C to +125C TO-220-5 MiC29373BU Adj 40C to +125C TO-263-5 * Junction temperatures Micrel Absolute Maximum Ratings lf 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 >t2000V 6-34MIC2937A/2937 1/29372/29373 Electrical Characteristics Micrel Limits in standard typeface are for T, = 25C and limits in boldface apply over the full operating temperature range. +1V,1 = 1mA, C, = 2.2uF. The MIC29372 and MIC29373 Feedback pins are tied Unless otherwise specified, V,, = V OUT to the 5V Tap, Output is tied to Output Sense (V,,, = 5V), and Vajuroown < 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 <1, < 500mA 5.0 4.880 5.120 Output Voltage Variation from designed V,,, -1 1 % Accuracy -2 2 5mA <1, < 500mA -2.5 2.5 AVo Output Voltage (Note 2) 20 100 | ppm/rc AT Temperature Coef. AV, Line Regulation Vy = 6V to 26V 0.03 0.10 % Vo. 0.40 AV, Load Regulation | =5 to 750mA 0.04 0.16 % Vo 0.20 (Note 3) VinVo Dropout Voitage | =5mA 60 100 mV (Note 4) 150 |, = 100mA 150 200 320 |, = 500mA 300 450 600 | = 750mA 370 leno Ground Pin Current | |, = 5mA 90 150 HA (Note 5) 180 |, = 100mA 1 2 mA 3 |, = 500mA 8 13 16 | = 750mA 15 leno Ground Pin V,, = 0.5V less than designed V.,,, 180 300 BA Current at Dropout (Note 5) Mann Current Limit Voyr = OV 1.0 1.5 A (Note 6) 2 AV, Thermal Regulation | (Note 7) 0.05 0.2 SolW AP, e, Output Noise C, =2.2uF 400 uv RMS Voltage (10Hz to 100kHz) | C, = 33nF 260 \ = 100mA 6-35MIC2937A/2937 1/29372/29373 Micrel Electrical Characteristics (Continued) MIC29372/MIC29373 Parameter Conditions Typ. Min Max Units Reference Voltage 1.235 1.210 1.260 Vv 1.200 1.270 V max Reference Voltage (Note 8) 1.185 1.285 Vv Feedback Pin 20 40 nA Bias Current 60 Reference Voltage (Note 7) 20 pem/*C Temperature Coefficient Feedback Pin Bias 0.1 nAfc Current Temperature Coefficient Error Comparator MIC29371/29373 Output Leakage Voy = 30V 0.01 1.00 HA Current 2.00 Output Low Vin = 45V 150 250 mV Voltage lo, = 250A 400 Upper Threshold (Note 9) 60 40 mV Voltage 25 Lower Threshold (Note 9) 75 95 mV Voltage 140 Hysteresis (Note 9) 15 mv Shutdown Input MIC29371/MIC 29372 Input Logic Voltage 1.3 Vv Low (ON} 0.7 High (OFF) 2.0 Shutdown Pin VeyuTDOWN =2.4V 30 50 HA input Current 100 Venutoown = 304 450 600 LA 750 Regulator Output (Note 10) 3 10 HA Current in Shutdown 20 6-36MIC2937A/2937 1/29372/29373 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 yay, = (Tyamax,7 14)/ 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 nominat 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 MIC2937A features fold-back current limiting. The short circuit (V,, |, = OV) current limit is less than the maximum current 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: Vi-- Vou, 5 (Vy 1:V). 2.3V 5 V,, $30V, SHA <I, < 750 MA, TST) yay 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 = Vour Noce = (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 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: Vasuroown 2 2 : Vin 30 V.Vouy = 9, 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. Schematic Diagram Ax aR Rai aa 6-37MIC2937A/2937 1/29372/29373 Typical Characteristics Ground Pin Current vs. Input Voltage 500 400 300 200 GROUND PIN CURRENT (A) 100 0 123 4 5 6 INPUT VOLTAGE (Vv) Ground Pin Current vs. Input Voltage 0 GROUND PIN CURRENT (mA) oO 12 3 4 5 6 INPUT VOLTAGE {) Ripple Rejection vs. Frequency at 0 Medium Current Vin = 6 Vout = Cy = 10uF RIPPLE REJECTION (dB) Ih 20 0.01 01 1 10 6100 FREQUENCY (kHz) INPUT OUTPUT VOLTAGE CHANGE (mV) VOLTAGE 7 8 7 8 1000 Line Transient Response 0 02 GROUND PIN CURRENT (pA) GROUND PIN CURRENT (mA) RIPPLE REJECTION (dB) Ground Pin Current vs. Temperature 259 200 150 Ihe 50 -75-50-25 0 25 50 75 100 125150 TEMPERATURE (C) Ground Pin Current vs. Temperature 9 pel 0 -75 -50-250 25 5075 100125 150 JUNCTION TEMPERATURE (-C} Ripple Rejection vs. Frequency at High Current 80 70 60 50 40 30 20 10 0.01 L= 1 = 500mA\ Vin = 6V Vout = C= 10pF 0.1 1 10 106 1000 FREQUENCY (kHz} =1 | L= 10mA Vv = OUTPUT VOLTAGE CHANGE (mV) ll EO at 23 > 04 06 08 1 0 1 TIME (mS) Ground Pin Current vs. Load 1 < E > 4 uu a rc ? 5 z a ge Z 0 9 c Oo 0.01 0.1 1 10 100 = 1000 OUTPUT CURRENT (mA) Output Noise Voltage a E 2 wu o = = a 5 > ul g Vin = 6V 8 Vout = 0.1 1 10 100 1C00 LOAD CURRENT (mA) Output Impedance 100 P P _ IN = a 10 IL=1 VouT = rit Cy = 10uF 3 21 a uw a 2 5 01 a Ee 2 6 0.01 : 0.01 01 1 10 100 1000 FREQUENCY (kHz! Line Transient Response =1 (= 10mA Vout = 2 3 4 5 TIME (mS) Micrel 6-38MIC2937A/2937 1/2937 2/29373 Typical Characteristics, Continued OUTPUT VOLTAGE CHANGE (mV) LOAD CURRENT OUTPUT VOLTAGE (V) SHUTDOWN VOLTAGE (V) OUTPUT VOLTAGE CHANGE (V) POWER DISSIPATION (W) -400 -800 500mA 100pA 0 Load Transient Vin = 6V 400 VouT = 0 10 20 30.040 TIME imS) jo Enable Transient 8 Ce 6 4 2 T= 10mA Vin = 14V 2 Vout = 0 1 2 3 4 TIME tmS) Thermal Q 10 20 30 40 TIME (mS) g_ 200 Vine <S AUT = se 100 Vout = SB oo k2Z ed -100 5o -200 zB QW 500mA 5 YS tou 5 G 10 20 30 40 50 60 TIME {mS} _ 6 2 Cl kb eo 4 58 og 2 > ~ 0 2> 20 2 Qa o 25 a> O 1 2 3 4 5 TIME (mS) 1200 Fold-Back Current Limiting = 1000 Z a ce r a Q 800 wo e 2 = 600 > a 400 Load Transient Response Enable Transient 0 20 40 60 83 100 PERCENT OUTPUT VOLTAGE (0) OUTPUT CURRENT (mA) OUTPUT VOLTAGE (V) DROPOUT VOL TAGE (V) 550 500 450 4c0 350 300 250 100 -75-50 -25 0 25 5075 100125150 Characteristics o 4 2 3 4 5 6 'NPUT VOLTAGE (VOLTS) Short-Circuit Output Current and Maximum Output Current MAX OUTPUT. OUT = SHORT CURRENT Vout =9 JUNCTION TEMPERATURE (-C1 Dropout Qo O02 #04 O86 O08 1.0 OUTPUT CURRENT (A) Micrel 6-39MIC2937A/2937 1/29372/29373 Applications Information External Capacitors A 10uF (or greater} capacitor is required between the MIC2937A 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 solidtantalums 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 0.5uF for current below 10mA or 0.15uF for currents below 1 mA. Adjusting the MIC29372/29373 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 750mA load at 1.23V output (Output shorted to Feedback) a 22uF (or greater) capacitor should be used. The MIC2937A 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 MIC29372/29373 version with external resistors, a minimum toad of 1mA is recommended. A 1uF capacitor should be placed from the 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 MIC29372/29373 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 atleast 22uF will remedy this. Error Detection Comparator Output (MIC29371/ MIC29373) Alogic low output will be produced by the comparator whenever the MIC29371/29373 output falls out of regulation by more than approximately 5%. This figure is the comparators 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 MiC29371/29373. For example, the error flag trip level is typically 4.75V for a 5V output or 11.4V fora 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 MiIC29371/29373 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 MIC29371/ 29373's dropout voltage is load-dependent (see curve in Typical Performance Characteristics), the input voltage trip Micrel point (about 5Y) 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 250A, 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. 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,,.,,- Programming the Output Voltage (MIC29372/ MIC29373) The MIC29372/29373 may be pin-strapped for 5V using theinternal 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 = Vacr X(1+A/Re} +157, 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 LA 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), le, 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 MIC29372/ 29373 typically draws 100 uA 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 capacitor. This is relatively inefficient, as increasing the capacitor from 1 uF to 220 pF only decreases the noise from 475V OUTPUT ' VOLTAGE | | | ERROR NOTF NOT ERROR vaLio VALIO INPUT Vv VOLTAGE 8 1.3V * SEE APPLICATIONS INFORMATION Figure 1. ERROR Output Timing 6-40MIC2937A/2937 1/29372/29373 Micrel 430uV to 160LV,,,, 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 1 27Ri * 200 Hz Ceypass = or about 0.01 uF. When doing this, the output capacitor must be increased to 10 uF to maintain stability. These changes reduce the output noise from 430 pV to 100 LV 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 MIC2937A 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 atlight ioads), and very low quiescent currents (100yA typical). These features are necessary for use in battery powered systems, such as automobiles. Itis a "bulletproof" device with the ability to survive both reverse battery (negative transients up to 20V below ground), and joad 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 5V + 2.2uF GND Ne L ! Figure 2. MIC2937A-5.0 Fixed +5V Regulator 1 *VOUT=VIN ERROR 5] VOUT UTPUT SHUTDOWN __ 3} INPUT =S=& _f7 OFF ON GND FB ls MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 40mV TO 400mv. DEPENDING ON LOAD CURRENT. Figure 4. MIC29372/29373 Wide Input Voltage Range Current Limiter *VIN VouT = V REF R 100kQ 8 x(1+ oa ) VIN VouT ERROR 5/ERROR V 1 | 12> 30V OUTPUT OUT T] 3 SPS A sp L. OFF _f- GND FB ON 1 7 av 4 VREF L I SEE APPLICATIONS INFORMATION Figure 3. MIC29372/29373 Adjustable Regulator NOTE: PINS 2 AND 6 ARE LEFT OPEN +7V +VIN Vec OUT 1 SHUTDOWN Vout INPUT SD f* ON T100pF soa 3.3nF GND FB 4 LL , 220k $ 180kR cr sv 470 ka % 11% iw S 2N2222 PIN 3 LOW= ENABLE OUTPUT. Q1 ON = 3.3V, Q1 OFF = 5.0V. Figure 5. MIC29372/29373 5.0V or 3.3V Selectable Regulator with Shutdown. 6-41