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Voltage Regulators
AN78xx/AN78xxF Series
3-pin positive output voltage regulator (1 A type)
I Overview
The AN78xx series and the AN78xxF series are 3pin, fixed positive output type monolithic voltage regulators. Stabilized fixed output voltage is obtained from unstable DC input voltage without using any external components. 11 types of fixed output voltage are available; 5V, 6V, 7V, 8V, 9V, 10V, 12V, 15V, 18V, 20V, and 24V. They can be used widely in power circuits with current capacity of up to 1A. AN78xx series
(10.35) 10.00.3 3.70.1
Unit: mm
4.50.2 1.40.1
15.40.2
(4.5)
1.4 +0.15 -0.05 0.8 +0.15 -0.05
I Features
* No external components * Output voltage: 5V, 6V, 7V, 8V, 9V, 10V, 12V, 15V, 18V, 20V, 24V * Built-in overcurrent limit circuit * Built-in thermal overload protection circuit * Built-in ASO (area of safe operation) protection circuit
(13.6)
2.54 2.54
0.45 +0.2 -0.0 (2.0) (2.5)
10.50.3
HSIP003-P-0000
AN78xxF series
10.500.30 5.30 (4.30) (1.73) 3.100.10
Unit: mm
2.770.30
16.700.30
17.000.25
13.600.25 4.500.25
2.54
(0.40) 0.800.20 2.000.25 1.400.20 4.500.30 1 2 3
0.40+0.10 -0.05 2.500.25
I Block Diagram
HSIP003-P-0000A
1 Pass Tr Q1 Current Source Current Limiter RSC 3
Input
Output
Starter
Voltage Reference
+ Error Amp. -
R2 Thermal Protection
R1 2
Common
8.700.30
4.200.25 3.800.25
12.50.2 17.00.2 26.10.2 29.00.3
8.70.2
2.90.1
1: Input 2: Common 3: Output
1: Input 2: Common 3: Output
1
AN78xx/AN78xxF Series
I Absolute Maximum Ratings at Ta = 25C
Parameter Input voltage Power dissipation AN78xx series AN78xxF series Symbol VI PD Topr Tstg Rating 35 *1 40 *2 15 *3 10.25 *3 -30 to +80 -55 to +150
Voltage Regulators
Unit V V W C C
Operating ambient temperature Storage temperature
*1 AN7805/F, AN7806/F, AN7807/F, AN7808/F, AN7809/F, AN7810/F, AN7812/F, AN7815/F, AN7818/F *2 AN7820/F, AN7824/F *3 Follow the derating curve. When Tj exceeds 150C, the internal circuit cuts off the output.
I Electrical Characteristics at Ta = 25C
* AN7805, AN7805F (5V type)
Parameter Output voltage Output voltage tolerance Line regulation Load regulation Bias current Bias current fluctuation to input Bias current fluctuation to load Output noise voltage Ripple rejection ratio Minimum input/output voltage difference Output impedance Output short-circuit current Peak output current Output voltage temperature coefficient Symbol VO VO REGIN REGL IBias IBias(IN) IBias(L) Vno RR VDIF(min) ZO IO(Short) IO(Peak) VO/Ta Conditions Tj = 25C VI = 8 to 20V, IO = 5mA to 1A, Tj = 0 to 125C, PD * VI = 7.5 to 25 V, Tj = 25C VI = 8 to 12V, Tj = 25C IO = 5mA to 1.5A, Tj = 25C IO = 250 to 750mA, Tj = 25C Tj = 25C VI = 7.5 to 25V, Tj = 25C IO = 5mA to 1A, Tj = 25C f = 10Hz to 100kHz VI = 8 to 18V, IO = 100mA, f = 120Hz IO = 1A, Tj = 25C f = 1kHz VI = 25V, Tj = 25C Tj = 25C IO = 5mA, Tj = 0 to 125C 62 2 17 700 2 - 0.3 40 Min 4.8 4.75 3 1 15 5 3.9 Typ 5 Max 5.2 5.25 100 50 100 50 8 1.3 0.5 Unit V V mV mV mV mV mA mA mA V dB V m mA A mV/C
Note 1) The specified condition Tj = 25C means that the test should be carried out within so short a test time (within 10ms) that the characteristic value drift due to the chip junction temperature rise can be ignored. Note 2) Unless otherwise specified, VI = 10V, IO = 500mA, CI = 0.33F and CO = 0.1F. * AN78xx series: 15W, AN78xxF series: 10.25W
2
Voltage Regulators
I Electrical Characteristics at Ta = 25C (continued)
* AN7806, 7806F (6V type)
Parameter Output voltage Output voltage tolerance Line regulation Load regulation Bias current Bias current fluctuation to input Bias current fluctuation to load Output noise voltage Ripple rejection ratio Minimum input/output voltage difference Output impedance Output short-circuit current Peak output current Output voltage temperature coefficient Symbol VO VO REGIN REGL IBias IBias(IN) IBias(L) Vno RR VDIF(min) ZO IO(Short) IO(Peak) VO/Ta Conditions Tj = 25C VI = 9 to 21V, IO = 5mA to 1A, Tj = 0 to 125C, PD * VI = 8.5 to 25V, Tj = 25C VI = 9 to 13V, Tj = 25C IO = 5mA to 1.5A, Tj = 25C IO = 250 to 750mA, Tj = 25C Tj = 25C VI = 8.5 to 25V, Tj = 25C IO = 5mA to 1A, Tj = 25C f = 10Hz to 100kHz
AN78xx/AN78xxF Series
Min 5.75 5.7
Typ 6
Max 6.25 6.3
Unit V V mV mV mV mV mA mA mA V dB V m mA A mV/C
5 1.5 14 4 3.9
120 60 120 60 8 1.3 0.5
40 59 2 17 700 2 - 0.4
VI = 9 to 19V, IO = 100mA, f = 120Hz IO = 1A, Tj = 25C f = 1kHz VI = 25V, Tj = 25C Tj = 25C IO = 5mA, Tj = 0 to 125C
Note 1) The specified condition Tj = 25C means that the test should be carried out within so short a test time (within 10ms) that the characteristic value drift due to the chip junction temperature rise can be ignored. Note 2) Unless otherwise specified, VI = 11V, IO = 500mA, CI = 0.33F and CO = 0.1F. * AN78xx series: 15W, AN78xxF series: 10.25W
* AN7807, 7807F (7V type)
Parameter Output voltage Output voltage tolerance Line regulation Load regulation Bias current Bias current fluctuation to input Bias current fluctuation to load Output noise voltage Ripple rejection ratio Minimum input/output voltage difference Output impedance Output short-circuit current Peak output current Output voltage temperature coefficient Symbol VO VO REGIN REGL IBias IBias(IN) IBias(L) Vno RR VDIF(min) ZO IO(Short) IO(Peak) VO/Ta Conditions Tj = 25C VI = 10 to 22V, IO = 5mA to 1A, Tj = 0 to 125C, PD * VI = 9.5 to 25V, Tj = 25C VI = 10 to 15V, Tj = 25C IO = 5mA to 1.5A, Tj = 25C IO = 250 to 750mA, Tj = 25C Tj = 25C VI = 9.5 to 25V, Tj = 25C IO = 5mA to 1A, Tj = 25C f = 10Hz to 100kHz VI = 10 to 20V, IO = 100mA, f = 120Hz IO = 1A, Tj = 25C f = 1kHz VI = 25V, Tj = 25C Tj = 25C IO = 5mA, Tj = 0 to 125C 57 2 16 700 2 - 0.5 46 Min 6.7 6.6 5 1.5 14 4 3.9 Typ 7 Max 7.3 7.4 140 70 140 70 8 1 0.5 Unit V V mV mV mV mV mA mA mA V dB V m mA A mV/C
Note 1) The specified condition Tj = 25C means that the test should be carried out within so short a test time (within 10ms) that the characteristic value drift due to the chip junction temperature rise can be ignored. Note 2) Unless otherwise specified, VI = 12V, IO = 500mA, CI = 0.33F and CO = 0.1F. * AN78xx series: 15W, AN78xxF series: 10.25W
3
AN78xx/AN78xxF Series
I Electrical Characteristics at Ta = 25C (continued)
* AN7808, 7808F (8V type)
Parameter Output voltage Output voltage tolerance Line regulation Load regulation Bias current Bias current fluctuation to input Bias current fluctuation to load Output noise voltage Ripple rejection ratio Minimum input/output voltage difference Output impedance Output short-circuit current Peak output current Output voltage temperature coefficient Symbol VO VO REGIN REGL IBias IBias(IN) IBias(L) Vno RR VDIF(min) ZO IO(Short) IO(Peak) VO/Ta Conditions Tj = 25C VI = 11 to 23V, IO = 5mA to 1A, Tj = 0 to 125C, PD * VI = 10.5 to 25V, Tj = 25C VI = 11 to 17V, Tj = 25C IO = 5mA to 1.5A, Tj = 25C IO = 250 to 750mA, Tj = 25C Tj = 25C VI = 10.5 to 25V, Tj = 25C IO = 5mA to 1A, Tj = 25C f = 10Hz to 100kHz VI = 11.5 to 21.5V, IO = 100mA, f = 120Hz IO = 1A, Tj = 25C f = 1kHz VI = 25V, Tj = 25C Tj = 25C IO = 5mA, Tj = 0 to 125C
Voltage Regulators
Min 7.7 7.6
Typ 8
Max 8.3 8.4
Unit V V mV mV mV mV mA mA mA V dB V m mA A mV/C
6 2 12 4 3.9
160 80 160 80 8 1 0.5
52 56 2 16 700 2 - 0.5
Note 1) The specified condition Tj = 25C means that the test should be carried out within so short a test time (within 10ms) that the characteristic value drift due to the chip junction temperature rise can be ignored. Note 2) Unless otherwise specified, VI = 14V, IO = 500mA, CI = 0.33F and CO = 0.1F. * AN78xx series: 15W, AN78xxF series: 10.25W
* AN7809, 7809F (9V type)
Parameter Output voltage Output voltage tolerance Line regulation Load regulation Bias current Bias current fluctuation to input Bias current fluctuation to load Output noise voltage Ripple rejection ratio Minimum input/output voltage difference Output impedance Output short-circuit current Peak output current Output voltage temperature coefficient Symbol VO VO REGIN REGL IBias IBias(IN) IBias(L) Vno RR VDIF(min) ZO IO(Short) IO(Peak) VO/Ta Conditions Tj = 25C VI = 12 to 24V, IO = 5mA to 1A, Tj = 0 to 125C, PD * VI = 11.5 to 26V, Tj = 25C VI = 12 to 18V, Tj = 25C IO = 5mA to 1.5A, Tj = 25C IO = 250 to 750mA, Tj = 25C Tj = 25C VI = 11.5 to 26V, Tj = 25C IO = 5mA to 1A, Tj = 25C f = 10Hz to 100kHz VI = 12 to 22V, IO = 100mA, f = 120Hz IO = 1A, Tj = 25C f = 1kHz VI = 26V, Tj = 25C Tj = 25C IO = 5mA, Tj = 0 to 125C 56 2 16 700 2 - 0.5 57 Min 8.65 8.55 7 2 12 4 3.9 Typ 9 Max 9.35 9.45 180 90 180 90 8 1 0.5 Unit V V mV mV mV mV mA mA mA V dB V m mA A mV/C
Note 1) The specified condition Tj = 25C means that the test should be carried out within so short a test time (within 10ms) that the characteristic value drift due to the chip junction temperature rise can be ignored. Note 2) Unless otherwise specified, VI = 15V, IO = 500mA, CI = 0.33F and CO = 0.1F. * AN78xx series: 15W, AN78xxF series: 10.25W
4
Voltage Regulators
I Electrical Characteristics at Ta = 25C (continued)
* AN7810, 7810F (10V type)
Parameter Output voltage Output voltage tolerance Line regulation Load regulation Bias current Bias current fluctuation to input Bias current fluctuation to load Output noise voltage Ripple rejection ratio Minimum input/output voltage difference Output impedance Output short-circuit current Peak output current Output voltage temperature coefficient Symbol VO VO REGIN REGL IBias IBias(IN) IBias(L) Vno RR VDIF(min) ZO IO(Short) IO(Peak) VO/Ta Conditions
AN78xx/AN78xxF Series
Min 9.6 9.5
Typ 10
Max 10.4 10.5
Unit V V mV mV mV mV mA mA mA V dB V m mA A mV/C
Tj = 25C VI = 13 to 25V, IO = 5mA to 1A, Tj = 0 to 125C, PD * VI = 12.5 to 27V, Tj = 25C VI = 13 to 19V, Tj = 25C IO = 5mA to 1.5A, Tj = 25C IO = 250 to 750mA, Tj = 25C Tj = 25C VI = 12.5 to 27V, Tj = 25C IO = 5mA to 1A, Tj = 25C f = 10Hz to 100kHz VI = 13 to 23V, IO = 100mA, f = 120Hz IO = 1A, Tj = 25C f = 1kHz VI = 27V, Tj = 25C Tj = 25C IO = 5mA, Tj = 0 to 125C
8 2.5 12 4 3.9
200 100 200 100 8 1 0.5
63 56 2 16 700 2 - 0.6
Note 1) The specified condition Tj = 25C means that the test should be carried out within so short a test time (within 10ms) that the characteristic value drift due to the chip junction temperature rise can be ignored. Note 2) Unless otherwise specified, VI = 16V, IO = 500mA, CI = 0.33F and CO = 0.1F. * AN78xx series: 15W, AN78xxF series: 10.25W
* AN7812, 7812F (12V type)
Parameter Output voltage Output voltage tolerance Line regulation Load regulation Bias current Bias current fluctuation to input Bias current fluctuation to load Output noise voltage Ripple rejection ratio Minimum input/output voltage difference Output impedance Output short-circuit current Peak output current Output voltage temperature coefficient Symbol VO VO REGIN REGL IBias IBias(IN) IBias(L) Vno RR VDIF(min) ZO IO(Short) IO(Peak) VO/Ta Conditions Tj = 25C VI = 15 to 27V, IO = 5mA to 1A, Tj = 0 to 125C, PD * VI = 14.5 to 30V, Tj = 25C VI = 16 to 22V, Tj = 25C IO = 5mA to 1.5A, Tj = 25C IO = 250 to 750mA, Tj = 25C Tj = 25C VI = 14.5 to 30V, Tj = 25C IO = 5mA to 1A, Tj = 25C f = 10Hz to 100kHz VI = 15 to 25V, IO = 100mA, f = 120Hz IO = 1A, Tj = 25C f = 1kHz VI = 30V, Tj = 25C Tj = 25C IO = 5mA, Tj = 0 to 125C 55 2 18 700 2 - 0.8 75 Min 11.5 11.4 10 3 12 4 4 Typ 12 Max 12.5 12.6 240 120 240 120 8 1 0.5 Unit V V mV mV mV mV mA mA mA V dB V m mA A mV/C
Note 1) The specified condition Tj = 25C means that the test should be carried out within so short a test time (within 10ms) that the characteristic value drift due to the chip junction temperature rise can be ignored. Note 2) Unless otherwise specified, VI = 19V, IO = 500mA, CI = 0.33F and CO = 0.1F. * AN78xx series: 15W, AN78xxF series: 10.25W
5
AN78xx/AN78xxF Series
I Electrical Characteristics at Ta = 25C (continued)
* AN7815, 7815F (15V type)
Parameter Output voltage Output voltage tolerance Line regulation Load regulation Bias current Bias current fluctuation to input Bias current fluctuation to load Output noise voltage Ripple rejection ratio Minimum input/output voltage difference Output impedance Output short-circuit current Peak output current Output voltage temperature coefficient Symbol VO VO REGIN REGL IBias IBias(IN) IBias(L) Vno RR VDIF(min) ZO IO(Short) IO(Peak) VO/Ta Conditions Tj = 25C VI = 18 to 30V, IO = 5mA to 1A, Tj = 0 to 125C, PD * VI = 17.5 to 30V, Tj = 25C VI = 20 to 26V, Tj = 25C IO = 5mA to 1.5A, Tj = 25C IO = 250 to 750mA, Tj = 25C Tj = 25C VI = 17.5 to 30V, Tj = 25C IO = 5mA to 1A, Tj = 25C f = 10Hz to 100kHz VI = 18.5 to 28.5V, f = 120Hz IO = 1A, Tj = 25C f = 1kHz VI = 30V, Tj = 25C Tj = 25C IO = 5mA, Tj = 0 to 125C
Voltage Regulators
Min 14.4 14.25
Typ 15
Max 15.6 15.75
Unit V V mV mV mV mV mA mA mA V dB V m mA A mV/C
11 3 12 4 4
300 150 300 150 8 1 0.5
90 54 2 19 700 2 -1
Note 1) The specified condition Tj = 25C means that the test should be carried out within so short a test time (within 10ms) that the characteristic value drift due to the chip junction temperature rise can be ignored. Note 2) Unless otherwise specified, VI = 23V, IO = 500mA, CI = 0.33F and CO = 0.1F. * AN78xx series: 15W, AN78xxF series: 10.25W
* AN7818, 7818F (18V type)
Parameter Output voltage Output voltage tolerance Line regulation Load regulation Bias current Bias current fluctuation to input Bias current fluctuation to load Output noise voltage Ripple rejection ratio Minimum input/output voltage difference Output impedance Output short-circuit current Peak output current Output voltage temperature coefficient Symbol VO VO REGIN REGL IBias IBias(IN) IBias(L) Vno RR VDIF(min) ZO IO(Short) IO(Peak) VO/Ta Conditions Tj = 25C VI = 21 to 33V, IO = 5mA to 1A, Tj = 0 to 125C, PD * VI = 21 to 33V, Tj = 25C VI = 24 to 30V, Tj = 25C IO = 5mA to 1.5A, Tj = 25C IO = 250 to 750mA, Tj = 25C Tj = 25C VI = 21 to 33V, Tj = 25C IO = 5mA to 1A, Tj = 25C f = 10Hz to 100kHz VI = 22 to 32V, IO = 100mA, f = 120Hz IO = 1A, Tj = 25C f = 1kHz VI = 35V, Tj = 25C Tj = 25C IO = 5mA, Tj = 0 to 125C 53 2 16 700 2 -1.1 110 Min 17.3 17.1 14 4 12 4 4.1 Typ 18 Max 18.7 18.9 360 180 360 180 8 1 0.5 Unit V V mV mV mV mV mA mA mA V dB V m mA A mV/C
Note 1) The specified condition Tj = 25C means that the test should be carried out within so short a test time (within 10ms) that the characteristic value drift due to the chip junction temperature rise can be ignored. Note 2) Unless otherwise specified, VI = 27V, IO = 500mA, CI = 0.33F and CO = 0.1F. * AN78xx series: 15W, AN78xxF series: 10.25W
6
Voltage Regulators
I Electrical Characteristics at Ta = 25C (continued)
* AN7820, 7820F (20V type)
Parameter Output voltage Output voltage tolerance Line regulation Load regulation Bias current Bias current fluctuation to input Bias current fluctuation to load Output noise voltage Ripple rejection ratio Minimum input/output voltage difference Output impedance Output short-circuit current Peak output current Output voltage temperature coefficient Symbol VO VO REGIN REGL IBias IBias(IN) IBias(L) Vno RR VDIF(min) ZO IO(Short) IO(Peak) VO/Ta Conditions
AN78xx/AN78xxF Series
Min 19.2 19
Typ 20
Max 20.8 21
Unit V V mV mV mV mV mA mA mA V dB V m mA A mV/C
Tj = 25C VI = 24 to 35V, IO = 5mA to 1A, Tj = 0 to 125C, PD * VI = 23 to 35V, Tj = 25C VI = 26 to 32V, Tj = 25C IO = 5mA to 1.5A, Tj = 25C IO = 250 to 750mA, Tj = 25C Tj = 25C VI = 23 to 35V, Tj = 25C IO = 5mA to 1A, Tj = 25C f = 10Hz to 100kHz VI = 24 to 34V, IO = 100mA, f = 120Hz IO = 1A, Tj = 25C f = 1kHz VI = 35V, Tj = 25C Tj = 25C IO = 5mA, Tj = 0 to 125C
15 5 12 4 4.1
400 200 400 200 8 1 0.5
110 53 2 22 700 2 -1.2
Note 1) The specified condition Tj = 25C means that the test should be carried out within so short a test time (within 10ms) that the characteristic value drift due to the chip junction temperature rise can be ignored. Note 2) Unless otherwise specified, VI = 29V, IO = 500mA, CI = 0.33F and CO = 0.1F. * AN78xx series: 15W, AN78xxF series: 10.25W
* AN7824, 7824F (24V type)
Parameter Output voltage Output voltage tolerance Line regulation Load regulation Bias current Bias current fluctuation to input Bias current fluctuation to load Output noise voltage Ripple rejection ratio Minimum input/output voltage difference Output impedance Output short-circuit current Peak output current Output voltage temperature coefficient Symbol VO VO REGIN REGL IBias IBias(IN) IBias(L) Vno RR VDIF(min) ZO IO(Short) IO(Peak) VO/Ta Conditions Tj = 25C VI = 28 to 38V, IO = 5mA to 1A, Tj = 0 to 125C, PD * VI = 27 to 38V, Tj = 25C VI = 30 to 36V, Tj = 25C IO = 5mA to 1.5A, Tj = 25C IO = 250 to 750mA, Tj = 25C Tj = 25C VI = 27 to 38V, Tj = 25C IO = 5mA to 1A, Tj = 25C f = 10Hz to 100kHz VI = 28 to 38V, IO = 100mA, f = 120Hz IO = 1A, Tj = 25C f = 1kHz VI = 38V, Tj = 25C Tj = 25C IO = 5mA, Tj = 0 to 125C 50 2 28 700 2 -1.4 170 Min 23 22.8 18 6 12 4 4.1 Typ 24 Max 25 25.2 480 240 480 240 8 1 0.5 Unit V V mV mV mV mV mA mA mA V dB V m mA A mV/C
Note 1) The specified condition Tj = 25C means that the test should be carried out within so short a test time (within 10ms) that the characteristic value drift due to the chip junction temperature rise can be ignored. Note 2) Unless otherwise specified, VI = 33V, IO = 500mA, CI = 0.33F and CO = 0.1F. * AN78xx series: 15W, AN78xxF series: 10.25W
7
AN78xx/AN78xxF Series
I Main Characteristic Curve
16 14 (1) 16 14
Voltage Regulators
Minimum input/output voltage difference VDIF(min.) (V)
PD Ta (AN78xx series)
PD Ta (AN78xxF series)
VDIF(min.) Tj
2.4
Power dissipation PD (W)
12 10 8 (3) 6 4 2 0
Power dissipation PD (W)
(2)
2.0
IO = 1A 500mA 200mA
12
(1)
1.6
10 8
(2)
1.2
20mA
6
(3)
0.8
0mA
4 2 0
0.4
(4) 0 40 80 120 160
(4)
0
40
80
120
160
0 -40
0
40
80
120
160
Ambient temperature Ta (C)
Ambient temperature Ta (C)
Junction temperature Tj (C)
Thermal resistance value: Rth(j-c) = 5C/W (max.) Rth(j-a) = 65C/W (max.) Installation condition to heat sink Tightening torque 6kg*cm Heat radiation compound used (1) (2) (3) (4) Infinite heat sink: 15.0W 5C/W heat sink: 12.5W 15C/W heat sink: 6.3W Without heat sink: 1.923W
Thermal resistance value: Rth(j-c) = 12.2C/W (max.) Rth(j-a) = 65C/W (max.) Installation condition to heat sink Tightening torque 6kg*cm Heat radiation compound used (1) Infinite heat sink: 10.25W (2) 5C/W heat sink: 7.3W (3) 15C/W heat sink: 4.5W (4) Without heat sink: 1.923W
Input transient response
Input voltage VI (V) Output voltage fluctuation (V)
20 AN7805 15
Load transient response
AN7805
Current limiting characteristic
Load current IO (A)
7 6 VI = 10V Tj = 25C AN7805 2
1
Output voltage VO (V)
5 4 3 2 1 0
10
Output voltage fluctuation (mV)
0 1
10
5
0
0
-10 -20
-1 -2
0
2
4
6
8
10
0
10
20
30
40
50
0
0.6
1.2
1.8
2.4
Time t (s)
Time t (s)
Output current IO (A)
8
Voltage Regulators
I Basic Regulator Circuit
Input 1 3 Output
AN78xx/AN78xxF Series
CI
AN78xx AN78xxF
2 Common
CO
CI : CI is necessary when the input line is long. CO: CO improves the transient response.
I Usage Notes
1. Cautions for a basic circuit
Di
VI 1 2 3
VO
CI
CO
Figure 1
CI: When a wiring from a smoothing circuit to a three-pin regulator is long, it is likely to oscillate in output. A capacitor of 0.1F to 0.47F should be connected near an input pin. CO: When any sudden change of load current is likely to occur, connect an electrolytic capacitor of 10F to 100F to improve a transitional response of output voltage. Di: Normally unnecessary. But add it in the case that there is a residual voltage at the output capacitor Co even after switching off the supply power because a current is likely to flow into an output pin of the IC and damage the IC.
2. Other caution items 1) Short-circuit between the input pin and GND pin If the input pin is short-circuitted to GND or is cut off when a large capacitance capacitor has been connected to the IC's load, a voltage of a capacitor connected to an output pin is applied between input/output of the IC and this likely results in damage of the IC. It is necessary, therefore, to connect a diode, as shown in figure 2, to counter the reverse bias between input/output pins.
In
1 2 GND
3
Out
Output
+ -
CO
Figure 2
2) Floating of GND pin If a GND pin is made floating in an operating mode, an unstabilized input voltage is outputted. In this case, a thermal protection circuit inside the IC does not normally operate. In this state, if the load is short-circuited or overloaded, it is likely to damage the IC.
I Application Circuit Examples
1. Current bootstrap circuit
VI Q1 3 1 0.33F 3
2. Adjustable output regulator
VI IO VO
1
AN78xx AN78xxF
2
3 VO' R2
AN78xx AN78xxF
2
VO 0.1F IBias R1
V' VO = VO' + IBias + RO R1 2 Note) VO varies due to sample to sample variation of IBias. Never fail to adjust individually with R1.
9

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