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LM2931-5.0

such as a load dump (60V) when the input voltage to the regulator can momentarily exceed the specified maximum operating voltage, the regulator will automatically shut down to protect both internal circuits and the load. The LM2931 can not be harmed by temporary mirror-image insertion. Familiar regulator features such as short circuit and thermal overload protection are also provided. Fixed output of 5V is available in the plastic the popular TO-92 package.
he LM2931 positive voltage regulator features a very low quiescent current of 1mA or less when supplying 10mA
loads. This unique characteristic and the extremely low in-putoutput differential required for proper regulation (0.2V for output currents of 10mA) make the LM2931 the ideal regulator for standby power systems. Applications include memory standby circuits, CMOS and other low power processor power supplies as well as systems demanding as much as 100mA of output current. Designed originally for automotive applications, the LM2931 and all regulated circuitry are protected from reverse battery installations or 2 battery jumps. During line transients,
TO-92

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Pin : 1. Output 2. Ground 3. Input

LM2931CT-5.0
LM2931ACT-5.0
5V
5V
TO-92
TO-92

1-6 2000/05 VER.A
LM2931-5.0

Input Voltage Operating Range Overvoltage Protection PJ2931 26V

50V
Internal Power Dissipation(Note 1) Operating Temperature Range Maximum Junction Temperature Storage Temperature Range Lead Temp.(Soldering, 10 seconds)
Internally Limited 0 70 125 to +150 210

(V=14V,Io=10mA, T =25(Note 1), C2=100F(unless otherwise specified)
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) V V V V mV mV mV m! mA mA mA mA
Output Voltage 6.0VV26V, Io 100mA -40Tj125 9VV16V 6VV26V 5mA
100mA 100mA and 10mArms, 100Hz-10KHz IomA6VV26V -40Tj125 Io=100mA,V=14V,Tj=25 10Hz-100KHz, C
=100 F
5
5.19 4.81 5.25 4.75
5.25 4.75 5.5 4.5
Line Regulation Load Regulation Output Impedance Quiescent Current
2 4 14 200 0.4 15 500 20
10 30 50 600 1.0 1.0 30 5 1000 50
2 4 14 200 0.4 15 500 20
10 30 50
1.0
1.0
Output Noise Voltage Long Term Stability Ripple Rejection Dropout Voltage

fo=120Hz Io=10mA Io=100mA
80
,
55 0.2 0.6
80
,
Maximum Operational Input 26 Voltage Maximum Line R=5005.5V,100ms 70 60 Transient Reverse Polarity -30 -15 Vo-0.3V, R=500! Input Voltage,DC Reverse Polarity 1% Duty Cycle, 100ms R=500! Input Voltage, -80 -50 Transient Note 1:To ensure constant junction temperature, low duty cycle pulse testing is used. Note 2:Guaranteed and 100% production tested.
0.3 33
0.3 33
0.2 0.6 26
mV /1000hr dB V V V V V
70 -30
50 -15
V -80 -50 V
Note 3:Guaranteed (but not 100% production tested)over the operating temperature and input current ranges. These limits are not used to calculate outgoing quality levels. Note 4:Thermal resistance junction-to-case (jc) is 3/W; case-to-ambient is 50/W.
2-6
LM2931-5.0

V=14V,V
=3V,I=10 mA, T =25(Note 1), R1=27K,C2=100"F(unless otherwise specified) '' Reference Voltage Io100mA, -40Tj125 R1=27K Measured from V
to Adjust Pin Output Voltage Range Line Regulation Load Regulation Output Impedance Quiescent Current V
+0.6VV26V 5mAIo100mA 100mA and 10mArms 100Hz-10KHz Io=10mA Io=100 mA During Shutdown R=500! Output Noise Voltage Long Term Stability Ripple Rejection Dropout Voltage Maximum Operational Input Voltage Maximum Line Transient Reverse Polarity Input Voltage, DC Reverse Polanty Input Voltage Transient On/Off Threshold Voltage Vo=3V On Off On/Off Threshold Current

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*+ 1.20
1.26 1.14 1.32 1.08 24 3
) V V V V V V mV /V %MAX
!/V
0.2 0.3 40 0.4 15 0.8 100
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1.5 1 1 1
mA mA mA Vrms/V %/1000hr %/V
10Hz-100KHz fo=120Hz Io10 mA Io=100 mA
0.02 0.05 0.3 33 0.2 0.6 26 60 -15 -50 1.2 3.25 50
V V V V V V V V A
Io=10 mA, Reference Voltage1.5V Vo-0.3V,R=500!
70 -30
1% Duty Cycle, T100msR=500! -80 2.0 2.2 20
3-6
LM2931-5.0
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4-6
LM2931-5.0
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2 *+,++, " " " 1Required if regulator located far from is 1Required if regulatoris located far from power supply filter. R1+R2 **C
must be at least 22"F to maintain V
=Reference Voltage stability. May be increased without R1 bound to maintain regulation during Note:Using 28K for R1 will transients. Locate as close as possible to automatically compensate for errors in the regulator.This capacitor must be rated temperature range as the regulator. The V
due to the input bias current of the the same equivalent series over ADJ pin(approximately 1"A) operating should resistance(ESR) of this capacitor be less than 1 over the td ti t t
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5-6
LM2931-5.0
++,3 One of the distinguishing factors of the LM2931 series regulators is the requirement of an output capacitor for device stability. The value required varies greatly depending upon the application circuit and other factors. Thus some comments on the characteristics of both capacitors and the regulator are in order. High frequency characteristics of electrolytic capacitors depend greatly on the type and even the manufacturer. As a result, a value of capacitance that works well with the LM2931 for one brand or type may not necessary be sufficient with an electrolytic of different origin. Sometimes actual bench testing, as described later, will be the only means to determine the proper capacitor and value. Experience has shown that, as a rule of thumb, the more expensive and higher quality electrolytics generally allow a smaller value for regulator stability. As an example, while a high-quality 100"F aluminum electrolytic covers all general application circuits, similar stability can be obtained with a tantalum electrolytic of only 47"F. This factor of two can generally be applied to any special application circuit also. Another critical characteristic of electrolytics is their performance over temperature. While the LM2931 is designed to operate to -40 , the same is not always true with all electrolytics(hot is generally not a problem). The electrolyte in many aluminum types will freeze around -30,reducing their effective value to zero. Since the capacitance is needed for regulator stability, the natural result is oscillation (and lots of it)at the regulator output. For all application circuits where cold operation is necessary, the output capacitor must be rated to operate at the minimum temperature. By coincidence, worst-case stability for the LM2931 also occurs at minimum temperatures. As a result, in applications where the regulator junction temperature will never be less than 25, the output capacitor can be reduced approximately by a factor of two over the value needed for the entire temperature range. To continue our example with the tantalum electrolytic, a value of only 22"F would probably thus suffice. For high-quality aluminum, 47"F would be adequate in such an application. Another regulator characteristic that is noteworthy is that stability decreases with higher output currents. This sensible fact has important connotations. In many applications, the LM2931 is operated at only a few milliamps of output current or less. In such a circuit, the output capacitor can be further reduced in value. As a rough estimation, a circuit that is required to deliver a maximum of 10mAof output current from the regulator would need an output capacitor of only half the value compared to the same regulator required to deliver the full output current of 100mA. If the example of the tantalum capacitor in the circuit rated at 25 junction temperature and above were continued to include a maximum of 10 mA of output current, then the 22#"F output capacitor could be reduced to only 10#"F.

In the case of the LM2931CT adjustable regulator, the minimum value of output capacitance is a function of the output voltage. As a general rule, the value decreases with higher output voltages, since internal loop gain is reduced. At this point, the procedure for bench testing the minimum value of an output capacitor in a special application circuit should be clear. Since worst-case occurs at minimum operating temperatures and maximum operating currents, the entire circuit, including the electrolytic, should be cooled to the minimum temperature. The input voltage to the regulator should be maintained at 0.6V above the output to keep internal power dissipation and die heating to a minimum. Worst-case occurs just after input power is applied and before the die has had a chance to heat up. Once the minimum value of capacitance has been found for the brand and type of electrolytic in question, the value should be doubled for actual use to account for production variations both in the capacitor and the regulator.(All the values in this section and the remainder of the data sheet were determined in this fashion.) --' '+ 4 The input-output voltage differential at which the circuit ceases to regulate against further reduction in input voltage. Measured when the output voltage has dropped 100 mV from the nominal value obtained at 14V input, dropout voltage is dependent upon load current and junction temperature. +4The DC voltage applied to the input terminals with respect to ground. +#+ --'4 The voltage difference between the unregulated input voltage and the regulated output voltage for which the regulator will operate. 4 The change in output voltage for a change in the input voltage. The measurement is made under conditions of low dissipation or by using pulse techniques such that the average chip temperature is not significantly affected. (4The change in output voltage for a change in load current at constant chip temperature. '
*4 Output voltage stability under accelerated life-test conditions after 1000 hours with maximum rated voltage and junction temperature. + 5 4 The rms AC voltage at the output, with constant load and no input ripple, measured over a specified frequency range. 6, ''4 That part of the positive input current that does not contribute to the positive load current. The regulator ground lead current. ++ 7,4 The ratio of the peak-to-peak input ripple voltage to the peak-to-peak output ripple voltage. +''
* - 4 The percentage change in output voltage for a thermal variation from room temperature true to either temperature extreme.

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