ON MC78T12ACT Three-ampere positive fixed voltage regulator Datasheet

Order this document by MC78T00/D
This family of fixed voltage regulators are monolithic integrated circuits
capable of driving loads in excess of 3.0 A. These three–terminal regulators
employ internal current limiting, thermal shutdown, and safe–area
compensation. Devices are available with improved specifications, including
a 2% output voltage tolerance, on AC–suffix 5.0, 12 and 15 V device types.
Although designed primarily as a fixed voltage regulator, these devices
can be used with external components to obtain adjustable voltages and
currents. This series of devices can be used with a series–pass transistor to
supply up to 15 A at the nominal output voltage.
• Output Current in Excess of 3.0 A
•
•
•
•
•
•
•
THREE–AMPERE
POSITIVE FIXED
VOLTAGE REGULATORS
SEMICONDUCTOR
TECHNICAL DATA
Power Dissipation: 25 W
No External Components Required
Output Voltage Offered in 2% and 4% Tolerance*
T SUFFIX
PLASTIC PACKAGE
CASE 221A
Thermal Regulation is Specified
Internal Thermal Overload Protection
Internal Short Circuit Current Limiting
Output Transistor Safe–Area Compensation
MAXIMUM RATINGS (TA = +25°C, unless otherwise noted.)
Rating
Input Voltage (5.0 V – 12 V)
Input Voltage (15 V)
Power Dissipation and Thermal Characteristics
Plastic Package (Note 1)
TA = +25°C
Thermal Resistance, Junction–to–Air
TC = +25°C
Thermal Resistance, Junction–to–Case
Storage Junction Temperature
Operating Junction Temperature Range
(MC78T00C, AC)
Symbol
Value
Unit
VI
35
40
Vdc
PD
RθJA
PD
RθJC
Pin 1. Input
2. Ground
3. Output
1
2
3
Heatsink surface is connected to Pin 2.
Internally Limited
65
°C/W
Internally Limited
2.5
°C/W
Tstg
+150
°C
TJ
0 to +125
°C
NOTES: 1. Although power dissipation is internally limited, specifications apply only
for PO ≤ Pmax, Pmax = 25 W.
DEVICE TYPE/NOMINAL OUTPUT VOLTAGE
MC78T05
MC78T08
5.0 V
8.0 V
MC78T12
MC78T15
12 V
15 V
ORDERING INFORMATION
Simplified Application
VO
Tol.
Operating
Temperature
Range
Package
MC78TXXCT
MC78TXXACT
4%
2%*
TJ = 0° to
+125°C
Plastic
Power
MC78TXXBT#
MC78TXXABT#
4%
2%*
TJ = – 40° to
+125°C
Plastic
Power
Device
Input
Cin*
0.33µF
MC78TXX
Output
CO**
A common ground is required between the input and the output voltages. The input voltage must
remain typically 2.2 V above the output voltage even during the low point on the input ripple voltage.
XX Indicates nominal voltage.
XX these two digits of the type number indicate voltage.
# Automotive temperature range selections are available with special test conditions and additional
tests. Contact your local Motorola sales office for
information.
** Cin is required if regulator is located an appreciable distance from power supply filter.
** (See Applications Information for details.)
** CO is not needed for stability; however, it does improve transient response.
* 2% regulators available in 5, 12 and 15 V devices.
 Motorola, Inc. 1996
MOTOROLA ANALOG IC DEVICE DATA
Rev 1
1
MC78T00 Series
ELECTRICAL CHARACTERISTICS (Vin = 10 V, IO = 3.0 A, 0°C ≤ TJ ≤ 125°C, PO ≤ Pmax [Note 1], unless otherwise noted.)
MC78T05AC
Characteristics
Output Voltage
(5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C)
(5.0 mA ≤ IO ≤ 3.0 A;
5.0 mA ≤ IO ≤ 2.0 A, 7.3 Vdc ≤ Vin ≤ 20 Vdc)
Symbol
Regline
Load Regulation (Note 2)
(5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C)
(5.0 mA ≤ IO ≤ 3.0 A)
Regload
Quiescent Current
(5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C)
(5.0 mA ≤ IO ≤ 3.0 A)
Typ
Max
Min
Typ
Max
4.9
4.8
5.0
5.0
5.1
5.2
4.8
4.75
5.0
5.0
5.2
5.25
–
3.0
25
–
3.0
25
–
–
10
15
30
80
–
–
10
15
30
80
–
0.001
0.01
–
0.002
0.03
–
–
3.5
4.0
5.0
6.0
–
–
3.5
4.0
5.0
6.0
VO
Line Regulation (Note 2)
(7.2 Vdc ≤ Vin ≤ 35 Vdc, IO = 5.0 mA, TJ = +25°C;
7.2 Vdc ≤ Vin ≤ 35 Vdc, IO = 1.0 A, TJ = +25°C;
8.0 Vdc ≤ Vin ≤ 12 Vdc, IO = 3.0 A, TJ = +25°C;
7.5 Vdc ≤ Vin ≤ 20 Vdc, IO = 1.0 A)
Thermal Regulation
(Pulse = 10 ms, P = 20 W, TA = +25°C)
MC78T05C
Min
Regtherm
Unit
Vdc
mV
mV
IB
%VO/W
mA
Quiescent Current Change
(7.2 Vdc ≤ Vin ≤ 35 Vdc, IO = 5.0 mA, TJ = +25°C;
5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C;
7.5 Vdc ≤ Vin ≤ 20 Vdc, IO = 1.0 A)
∆IB
–
0.3
1.0
–
0.3
1.0
mA
Ripple Rejection
(8.0 Vdc ≤ Vin ≤ 18 Vdc, f = 120 Hz,
IO = 2.0 A, TJ = 25°C)
RR
62
75
–
62
75
–
dB
Dropout Voltage (IO = 3.0 A, TJ = +25°C)
Vin–VO
–
2.2
2.5
–
2.2
2.5
Vdc
Output Noise Voltage
(10 Hz ≤ f ≤ 100 kHz, TJ = +25°C)
Vn
–
10
–
–
10
–
µV/VO
Output Resistance (f = 1.0 kHz)
RO
–
2.0
–
–
20
–
mΩ
Short Circuit Current Limit
(Vin = 35 Vdc, TJ = +25°C)
ISC
–
1.5
–
–
1.5
–
A
Peak Output Current (TJ = +25°C)
Imax
–
5.0
–
–
5.0
–
A
TCVO
–
0.2
–
–
0.2
–
mV/°C
Average Temperature Coefficient of Output Voltage
(IO = 5.0 mA)
NOTES: 1. Although power dissipation is internally limited, specifications apply only for PO ≤ Pmax, Pmax = 25 W.
2. Line and load regulation are specified at constant junction temperature. Changes in VO due to heating effects must be taken into account separately.
Pulse testing with low duty cycle is used.
2
MOTOROLA ANALOG IC DEVICE DATA
MC78T00 Series
ELECTRICAL CHARACTERISTICS (Vin = 13 V, IO = 3.0 A, 0°C ≤ TJ ≤ 125°C, PO ≤ Pmax [Note 1], unless otherwise noted.)
MC78T08C
Characteristics
Output Voltage
(5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C)
(5.0 mA ≤ IO ≤ 3.0 A;
5.0 mA ≤ IO ≤ 2.0 A, 10.4 Vdc ≤ Vin ≤ 23 Vdc)
Symbol
Regline
Load Regulation (Note 2)
(5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C)
(5.0 mA ≤ IO ≤ 3.0 A)
Regload
Quiescent Current
(5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C)
(5.0 mA ≤ IO ≤ 3.0 A)
Typ
Max
7.7
7.6
8.0
8.0
8.3
8.4
–
4.0
35
–
–
10
15
30
80
–
0.002
0.03
–
–
3.5
4.0
5.0
6.0
VO
Line Regulation (Note 2)
(10.3 Vdc ≤ Vin ≤ 35 Vdc, IO = 5.0 mA, TJ = +25°C
10.3 Vdc ≤ Vin ≤ 35 Vdc, IO = 1.0 A, TJ = +25°C
11 Vdc ≤ Vin ≤ 17 Vdc, IO = 3.0 A, TJ = +25°C
10.7 Vdc ≤ Vin ≤ 23 Vdc, IO = 1.0 A)
Thermal Regulation
(Pulse = 10 ms, P = 20 W, TA = +25°C)
Min
Regtherm
Unit
Vdc
mV
mV
IB
%VO/W
mA
Quiescent Current Change
(10.3 Vdc ≤ Vin ≤ 35 Vdc, IO = 5.0 mA, TJ = +25°C;
5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C;
10.7 Vdc ≤ Vin ≤ 23 Vdc, IO = 1.0 A)
∆IB
–
0.3
1.0
mA
Ripple Rejection
(11 Vdc ≤ Vin ≤ 21 Vdc, f = 120 Hz, IO = 2.0 A, TJ = 25°C)
RR
60
71
–
dB
Vin–VO
–
2.2
2.5
Vdc
Output Noise Voltage
(10 Hz ≤ f ≤ 100 kHz, TJ = +25°C)
Vn
–
10
–
µV/VO
Output Resistance (f = 1.0 kHz)
RO
–
2.0
–
mΩ
Short Circuit Current Limit
(Vin = 35 Vdc, TJ = +25°C)
ISC
–
1.5
–
A
Peak Output Current (TJ = +25°C)
Imax
–
5.0
–
A
TCVO
–
0.3
–
mV/°C
Dropout Voltage (IO = 3.0 A, TJ = +25°C)
Average Temperature Coefficient of Output Voltage (IO = 5.0 mA)
NOTES: 1. Although power dissipation is internally limited, specifications apply only for PO ≤ Pmax, Pmax = 25 W.
2. Line and load regulation are specified at constant junction temperature. Changes in VO due to heating effects must be taken into account separately.
Pulse testing with low duty cycle is used.
MOTOROLA ANALOG IC DEVICE DATA
3
MC78T00 Series
ELECTRICAL CHARACTERISTICS (Vin = 17 V, IO = 3.0 A, 0°C ≤ TJ ≤ 125°C, PO ≤ Pmax [Note 1], unless otherwise noted.)
MC78T12AC
Characteristics
Output Voltage
(5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C)
(5.0 mA ≤ IO ≤ 3.0 A,
5.0 mA ≤ IO ≤ 2.0 A, 14.5 Vdc ≤ Vin ≤ 27 Vdc)
Symbol
Regline
Load Regulation (Note 2)
(5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C)
(5.0 mA ≤ IO ≤ 3.0 A)
Regload
Quiescent Current
(5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C)
(5.0 mA ≤ IO ≤ 3.0 A)
Typ
Max
Min
Typ
Max
11.75
11.5
12
12
12.25
12.5
11.5
11.4
12
12
12.5
12.6
–
6.0
45
–
6.0
45
–
–
10
15
30
80
–
–
10
15
30
80
–
0.001
0.01
–
0.002
0.03
–
–
3.5
4.0
5.0
6.0
–
–
3.5
4.0
5.0
6.0
VO
Line Regulation (Note 2)
(14.5 Vdc ≤ Vin ≤ 35 Vdc, IO = 5.0 mA, TJ = +25°C;
14.5 Vdc ≤ Vin ≤ 35 Vdc, IO = 1.0 A, TJ = +25°C;
16 Vdc ≤ Vin ≤ 22 Vdc, IO = 3.0 A, TJ = +25°C;
14.9 Vdc ≤ Vin ≤ 27 Vdc, IO = 1.0 A)
Thermal Regulation
(Pulse = 10 ms, P = 20 W, TA = +25°C)
MC78T12C
Min
Regtherm
Unit
Vdc
mV
mV
IB
%VO/W
mA
Quiescent Current Change
(14.5 Vdc ≤ Vin ≤ 35 Vdc, IO = 5.0 mA, TJ = +25°C;
5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C;
14.9 Vdc ≤ Vin ≤ 27 Vdc, IO = 1.0 A)
∆IB
–
0.3
1.0
–
0.3
1.0
mA
Ripple Rejection
(15 Vdc ≤ Vin ≤ 25 Vdc, f = 120 Hz,
IO = 2.0 A, TJ = 25°C)
RR
57
67
–
57
67
–
dB
Dropout Voltage (IO = 3.0 A, TJ = +25°C)
Vin – VO
–
2.2
2.5
–
2.2
2.5
Vdc
Output Noise Voltage
(10 Hz ≤ f ≤ 100 kHz, TJ = +25°C)
Vn
–
10
–
–
10
–
µV/VO
Output Resistance (f = 1.0 kHz)
RO
–
2.0
–
–
20
–
mΩ
Short Circuit Current Limit
(Vin = 35 Vdc, TJ = +25°C)
ISC
–
1.5
–
–
1.5
–
A
Peak Output Current (TJ = +25°C)
Imax
–
5.0
–
–
5.0
–
A
Average Temperature Coefficient
of Output Voltage (IO = 5.0 mA)
TCVO
–
0.5
–
–
0.5
–
mV/°C
NOTES: 1. Although power dissipation is internally limited, specifications apply only for PO ≤ Pmax, Pmax = 25 W.
2. Line and load regulation are specified at constant junction temperature. Changes in VO due to heating effects must be taken into account separately.
Pulse testing with low duty cycle is used.
4
MOTOROLA ANALOG IC DEVICE DATA
MC78T00 Series
ELECTRICAL CHARACTERISTICS (Vin = 20 V, IO = 3.0 A, 0°C ≤ TJ ≤ 125°C, PO ≤ Pmax [Note 1], unless otherwise noted.)
MC78T15AC
Characteristics
Output Voltage
(5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C)
(5.0 mA ≤ IO ≤ 3.0 A;
5.0 mA ≤ IO ≤ 2.0 A, 17.5 Vdc ≤ Vin ≤ 30 Vdc)
Symbol
Regline
Load Regulation (Note 2)
(5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C)
(5.0 mA ≤ IO ≤ 3.0 A)
Regload
Quiescent Current
(5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C)
(5.0 mA ≤ IO ≤ 3.0 A)
Typ
Max
Min
Typ
Max
14.7
14.4
15
15
15.3
15.6
14.4
14.25
15
15
15.6
15.75
–
7.5
55
–
7.5
55
–
–
10
15
30
80
–
–
10
15
30
80
–
0.001
0.01
–
0.002
0.03
–
–
3.5
4.0
5.0
6.0
–
–
3.5
4.0
5.0
6.0
VO
Line Regulation (Note 2)
(17.6 Vdc ≤ Vin ≤ 40 Vdc, IO = 5.0 mA, TJ = +25°C;
17.6 Vdc ≤ Vin ≤ 40 Vdc, IO = 1.0 A, TJ = +25°C;
20 Vdc ≤ Vin ≤ 26 Vdc, IO = 3.0 A, TJ = +25°C;
18 Vdc ≤ Vin ≤ 30 Vdc, IO = 1.0 A)
Thermal Regulation
(Pulse = 10 ms, P = 20 W, TA = +25°C)
MC78T15C
Min
Regtherm
Unit
Vdc
mV
mV
IB
%VO/W
mA
Quiescent Current Change
(17.6 Vdc ≤ Vin ≤ 40 Vdc, IO = 5.0 mA, TJ = +25°C;
5.0 mA ≤ IO ≤ 3.0 A, TJ = +25°C;
18 Vdc ≤ Vin ≤ 30 Vdc, IO = 1.0 A)
∆IB
–
0.3
1.0
–
0.3
1.0
mA
Ripple Rejection
(18.5 Vdc ≤ Vin ≤ 28.5 Vdc, f = 120 Hz,
IO = 2.0 A, TJ = 25°C)
RR
55
65
–
55
65
–
dB
Dropout Voltage (IO = 3.0 A, TJ = +25°C)
Vin–VO
–
2.2
2.5
–
2.2
2.5
Vdc
Output Noise Voltage
(10 Hz ≤ f ≤ 100 kHz, TJ = +25°C)
Vn
–
10
–
–
10
–
µV/VO
Output Resistance (f = 1.0 kHz)
RO
–
2.0
–
–
20
–
mΩ
Short Circuit Current Limit
(Vin = 40 Vdc, TJ = +25°C)
ISC
–
1.0
–
–
1.0
–
A
Peak Output Current (TJ = +25°C)
Imax
–
5.0
–
–
5.0
–
A
TCVO
–
0.6
–
–
0.6
–
mV/°C
Average Temperature Coefficient of Output Voltage
(IO = 5.0 mA)
NOTES: 1. Although power dissipation is internally limited, specifications apply only for PO ≤ Pmax, Pmax = 25 W.
2. Line and load regulation are specified at constant junction temperature. Changes in VO due to heating effects must be taken into account separately.
Pulse testing with low duty cycle is used.
MOTOROLA ANALOG IC DEVICE DATA
5
MC78T00 Series
VOLTAGE REGULATOR PERFORMANCE
Figure 1. MC78T05AC Line and Thermal Regulation
Figure 2. MC78T05AC Load and Thermal Regulation
2
2
1
(2.0 mV/DIV)
18
8.0
2
1
2
2.0
0
t, TIME (2.0 ms/DIV)
t, TIME (2.0 ms/DIV)
Vout = 5.0 V
Vin = 8.0 V → 18 V → 8.0 V
Iout = 2.0 A
(2.0 mV/DIV)
I O , OUTPUT ∆ V O , OUTPUT
CURRENT (A)
VOLTAGE DEVIATION (V)
can be caused by a change in either the input voltage or the
load current. Thermal regulation is a function of IC layout and
die attach techniques, and usually occurs within 10 ms of a
change in power dissipation. After 10 ms, additional changes
in the output voltage are due to the temperature coefficient of
the device.
Figure 1 shows the line and thermal regulation response of
a typical MC78T05AC to a 20 W input pulse. The variation of
the output voltage due to line regulation is labeled ➀ and the
thermal regulation component is labeled ➁. Figure 2 shows
the load and thermal regulation response of a typical
MC78T05AC to a 20 W load pulse. The output voltage
variation due to load regulation is labeled ➀ and the thermal
regulation component is labeled ➁.
∆ V O , OUTPUT
V in , INPUT VOLTAGE DEVIATION (V)
VOLTAGE (V)
The performance of a voltage regulator is specified by its
immunity to changes in load, input voltage, power dissipation,
and temperature. Line and load regulation are tested with a
pulse of short duration (< 100µs) and are strictly a function of
electrical gain. However, pulse widths of longer duration (>
1.0 ms) are sufficient to affect temperature gradients across
the die. These temperature gradients can cause a change in
the output voltage, in addition to changes caused by line and
load regulation. Longer pulse widths and thermal gradients
make it desirable to specify thermal regulation.
Thermal regulation is defined as the change in output
voltage caused by a change in dissipated power for a
specified time, and is expressed as a percentage output
voltage change per watt. The change in dissipated power
Vout = 5.0 V
Vin = 15
Iout = 0 A → 2.0 A → 0 A
1 = Regline = 2.4 mV
2 = Regtherm = 0.0015%VO/W
1 = Regline = 4.4 mV
2 = Regtherm = 0.0015%VO/W
Representative Schematic Diagram
Q1
1.0k
Input
1.0k
Q2
Q20
Q22
6.7V
210
Q21
16k
Q24
Q9
Q3
Q4
3.0k
3.6k
Q19
5.6k
6.4k
Q5
Q6
Q11
Q13
Q7
6.0k
6
Q27
13
200
0.12
Output
40
pF
Q12
2.0k
Q26
300
50
520
2.6k 8.0–15 VO
5.0 VO
3.9k
10pF
Q23
Q16
Q10
Q25
200
1.0k
Q8
300
100
6.0k
Q17
Q18
Q15
Q14
2.8k
Gnd
MOTOROLA ANALOG IC DEVICE DATA
MC78T00 Series
Figure 3. Temperature Stability
Figure 4. Output Impedance
100
r O , OUTPUT IMPEDANCE ( Ω )
NORMALIZED OUTPUT VOLTAGE
1.02
Vin – Vout = 10 V
Iout = 100 mA
1.0
.98
–90
–50
–10
30
70
110
TJ, JUNCTION TEMPERATURE (°C)
150
10–1
10–2
10–3
10–4
1.0
190
RR, RIPPLE REJECTION (dB)
Iout = 50 mA
80
Iout = 1.5 A
60
Vout = 5.0 V
Vin = 10 V
CO = 0
TJ = 25°C
40
20
1.0
4.0
10
100 1.0 k
10 k
100 k
1.0 M
10 M
1.0 k
10 k 100 k
f, FREQUENCY (Hz)
1.0 M
10 M 100 M
Vout = 5.0 V
Vin = 10 V
CO = 0
f = 120 Hz
TJ = 25°C
40
0.1
1.0
10
Iout, OUTPUT CURRENT (A)
Figure 7. Quiescent Current versus
Input Voltage
Figure 8. Quiescent Current versus
Output Current
5.0
TJ = 25°C
3.0
TJ = 125°C
2.0
TJ = 0°C
TJ = 25°C
TJ = 125°C
0
60
f, FREQUENCY (Hz)
TJ = 0°C
1.0
80
30
0.01
100 M
IB , QUIESCENT CURRENT (mA)
RR, RIPPLE REJECTION (dB)
100
100
100
IB , QUIESCENT CURRENT (mA)
10
Figure 6. Ripple Rejection versus
Output Current
Figure 5. Ripple Rejection versus Frequency
0
Vout = 5.0 V
Vin = 7.5 V
Iout = 1.0 A
CO = 0
TJ = 25°C
10
20
Vin, INPUT VOLTAGE (Vdc)
MOTOROLA ANALOG IC DEVICE DATA
30
40
TJ = 0°C
4.0
TJ = 25°C
3.0
TJ = 125°C
2.0
1.0
0
0.01
Vin–Vout = 5.0 V
0.1
1.0
10
Iout, OUTPUT CURRENT (A)
7
MC78T00 Series
Figure 9. Dropout Voltage
Figure 10. Peak Output Current
8.0
I max, PEAK OUTPUT CURRENT (A)
V in –Vout , INPUT TO OUTPUT
VOLTAGE DIFFERENTIAL (Vdc)
2.5
Iout = 3.0 A
2.0
Iout = 1.0 A
1.5
Iout = 0.5 A
1.0
∆VO = 50 mV
0.5
–90
6.0
4.0
2.0
TJ = 0°C
TJ = 25°C
TJ = 125°C
0
–50
–10
30
70
110
150
190
0
10
TJ, JUNCTION TEMPERATURE (°C)
8
I out , OUTPUT ∆ V out , OUTPUT VOLTAGE
DEVIATION (V)
CURRENT (A)
0.4
0.2
0
–0.2
–0.4
–0.6
1.0
0.5
0
0
10
20
30
40
Figure 12. Load Transient Response
Vout = 5.0 V
Iout = 150 mA
CO = 0
TJ = 25°C
30
0.3
Vin = 10 V
CO = 0
TJ = 25°C
0.2
0.1
0
–0.1
–0.2
–0.3
1.5
1.0
0.5
0
0
40
10
20
30
40
t, TIME (µs)
t, TIME (µs)
P D(AV) , MAXIMUM AVERAGE POWER DISSIPATION (W)
∆ Vin , INPUT VOLTAGE
CHANGE (V)
∆ V out , OUTPUT VOLTAGE
DEVIATION (V)
Figure 11. Line Transient Response
0.8
0.6
20
Vin–VO, INPUT–OUTPUT VOLTAGE (Vdc)
Figure 13. Maximum Average Power
Dissipation for MC78T00CT, ACT
40
30
Maximum Ambient
Temperature
θSA of Heatsinks
1.3°C/W
2.4°C/W
Infinite
Heatsink
20
3.3°C/W
10 6.3°C/W
10.5°C
0
25
50
75
100
125
TA, AMBIENT TEMPERATURE (°C)
MOTOROLA ANALOG IC DEVICE DATA
MC78T00 Series
APPLICATIONS INFORMATION
Design Considerations
The MC78T00 Series of fixed voltage regulators are
designed with Thermal Overload Protection that shuts down
the circuit when subjected to an excessive power overload
condition, Internal Short Circuit Protection that limits the
maximum current the circuit will pass, and Output Transistor
Safe–Area Compensation that reduces the output short
circuit current as the voltage across the pass transistor is
increased.
In many low current applications, compensation
capacitors are not required. However, it is recommended that
the regulator input be bypassed with a capacitor if the
regulator is connected to the power supply filter with long wire
lengths, or if the output load capacitance is large. An input
bypass capacitor should be selected to provide good high
frequency characteristics to insure stable operation under all
load conditions. A 0.33 µF or larger tantalum, mylar, or other
capacitor having low internal impedance at high frequencies
should be chosen. The bypass capacitor should be mounted
with the shortest possible leads directly across the regulator’s
input terminals. Normally good construction techniques
should be used to minimize ground loops and lead resistance
drops since the regulator has no external sense lead.
Figure 14. Current Regulator
Figure 15. Adjustable Output Regulator
MC78T05
Input
Output
R
0.33µF
MC78T05
Constant
Current to
Grounded Load
Input
IO
The MC78T05 regulator can also be used as a current source when
connected as above. In order to minimize dissipation the MC78T05 is
chosen in this application. Resistor R determines the current
as follows:
5.0 V
IO = R + IB
^
^
∆IB 0.7 mA over line, load and Temperature changes
IB 3.5 mA
For example, a 2.0 A current source would require R to be a 2.5 Ω,
10 W resistor and the output voltage compliance would be the input
voltage less 7.0 V.
7
0.1µF
+
3
10k
4
MC1741
VO, 8.0 V to 20 V
Vin – VO ≥ 2.5 V
The addition of an operational amplifier allows adjustment to higher or
intermediate values while retaining regulation characteristics. The
minimum voltage obtainable with this arrangement is 3.0 V greater
than the regulator voltage.
Figure 17. Current Boost With
Short Circuit Protection
2N4398 or Equiv
Input
MC78TXX
2
6
1.0k
Figure 16. Current Boost Regulator
R
–
0.33µF
Rsc
Output
2N4398
or Equiv.
MJ2955
or Equiv.
R
MC78TXX
1.0µF
0.1µF
Output
1.0µF
XX = 2 digits of type number indicating voltage.
The MC78T00 series can be current boosted with a PNP transistor. The
2N4398 provides current to 15 A. Resistor R in conjuction with the VBE of
the PNP determines when the pass transistor begins conducting; this
circuit is not short circuit proof. Input–output differential voltage
minimum is increased by the VBE of the pass transistor.
MOTOROLA ANALOG IC DEVICE DATA
XX = 2 digits of type number indicating voltage.
The circuit of Figure 17 can be modified to provide supply protection
against short circuits by adding a short circuit sense resistor, RSC, and
an additional PNP transistor. The current sensing PNP must be able to
handle the short circuit current of the three–terminal regulator.
Therefore, an eight–ampere power transistor is specified.
9
MC78T00 Series
OUTLINE DIMENSIONS
T SUFFIX
PLASTIC PACKAGE
CASE 221A–06
ISSUE Y
–T–
B
C
F
T
S
4
A
Q
1 2 3
U
H
K
Z
L
R
V
J
G
D
N
10
SEATING
PLANE
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
3. DIMENSION Z DEFINES A ZONE WHERE ALL
BODY AND LEAD IRREGULARITIES ARE
ALLOWED.
DIM
A
B
C
D
F
G
H
J
K
L
N
Q
R
S
T
U
V
Z
INCHES
MIN
MAX
0.570
0.620
0.380
0.405
0.160
0.190
0.025
0.035
0.142
0.147
0.095
0.105
0.110
0.155
0.018
0.025
0.500
0.562
0.045
0.060
0.190
0.210
0.100
0.120
0.080
0.110
0.045
0.055
0.235
0.255
0.000
0.050
0.045
–––
–––
0.080
MILLIMETERS
MIN
MAX
14.48
15.75
9.66
10.28
4.07
4.82
0.64
0.88
3.61
3.73
2.42
2.66
2.80
3.93
0.46
0.64
12.70
14.27
1.15
1.52
4.83
5.33
2.54
3.04
2.04
2.79
1.15
1.39
5.97
6.47
0.00
1.27
1.15
–––
–––
2.04
MOTOROLA ANALOG IC DEVICE DATA
MC78T00 Series
Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty, representation or guarantee regarding
the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and
specifically disclaims any and all liability, including without limitation consequential or incidental damages. “Typical” parameters which may be provided in Motorola
data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals”
must be validated for each customer application by customer’s technical experts. Motorola does not convey any license under its patent rights nor the rights of
others. Motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other
applications intended to support or sustain life, or for any other application in which the failure of the Motorola product could create a situation where personal injury
or death may occur. Should Buyer purchase or use Motorola products for any such unintended or unauthorized application, Buyer shall indemnify and hold Motorola
and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees
arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that Motorola
was negligent regarding the design or manufacture of the part. Motorola and
are registered trademarks of Motorola, Inc. Motorola, Inc. is an Equal
Opportunity/Affirmative Action Employer.
MOTOROLA ANALOG IC DEVICE DATA
11
MC78T00 Series
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12
◊
*MC78T00/D*
MOTOROLA ANALOG IC DEVICE
DATA
MC78T00/D
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