MC7808

Part: MC78xx/NCV78xx Series — ON Semiconductor Type: Positive Fixed-Voltage Regulator Description: Monolithic integrated circuits designed as fixed-voltage regulators for a wide variety of applications, capable of delivering output currents in excess of 1.0 A with internal current limiting, thermal shutdown, and safe-area compensation.

Operating Conditions:

• Operating junction temperature: up to +150 °C

Absolute Maximum Ratings:

• Max input voltage: 35 Vdc (for 5.0-18V output variants)
• Max storage junction temperature: -65 to +150 °C
• Max operating junction temperature: +150 °C

Key Specs:

• Output Voltage (MC7805B, T J = 25 °C): 4.8 V (min), 5.0 V (typ), 5.2 V (max)
• Output Voltage (MC7808B, T J = 25 °C): 7.7 V (min), 8.0 V (typ), 8.3 V (max)
• Output Voltage (MC7812B, T J = 25 °C): 11.5 V (min), 12 V (typ), 12.5 V (max)
• Output Voltage (MC7815B, T J = 25 °C): 14.4 V (min), 15 V (typ), 15.6 V (max)
• Dropout Voltage (I O = 1.0 A, T J = 25 °C): 2.0 V (typ)
• Quiescent Current (MC7805B): 3.2 mA (typ), 8.0 mA (max)
• Ripple Rejection (MC7805B, 8.0 Vdc ≤ V in ≤ 18 Vdc, f = 120 Hz): 68 dB (typ)
• Peak Output Current (T J = 25 °C): 2.2 A (typ)

Features:

• No External Components Required
• Output Current in Excess of 1.0 A
• Internal Thermal Overload Protection
• Output Transistor Safe-Area Compensation
• Internal Short Circuit Current Limiting
• Output Voltage Offered in 1.5%, 2% and 4% Tolerance
• NCV Prefix for Automotive and Other Applications Requiring Unique Site and Control Change Requirements; AEC-Q100 Qualified and PPAP Capable
• Available in Surface Mount D2PAK-3, DPAK-3 and Standard 3-Lead Transistor Packages
• Pb-Free Devices

Applications:

• Local, on-card regulation

Package:

• TO-220 T Suffix Case 221AB
• D2PAK-3 D2T Suffix Case 936
• DPAK-3 DT Suffix Case 369C

• No External Components Required
• Output Current in Excess of 1.0 A
• Internal Thermal Overload Protection
• Output Transistor Safe -Area Compensation
• Internal Short Circuit Current Limiting
• Output Voltage Offered in 1.5%, 2% and 4% Tolerance
• NCV Prefix for Automotive and Other Applications Requiring Unique Site and Control Change Requirements; AEC -Q100 Qualified and PPAP Capable
• Available in Surface Mount D 2 PAK -3, DPAK -3 and Standard 3 -Lead Transistor Packages
• These are Pb -Free Devices

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 m F 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 regulators 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.

The MC7800 regulators can also be used as a current source when connected as above. In order to minimize dissipation the MC7805C is chosen in this application. Resistor R determines the current as follows:

I B ^ 3.2 mA over line and load changes.

For example, a 1.0 A current source would require R to be a 5.0 W , 10 W resistor and the output voltage compliance would be the input voltage less 7.0 V.

Figure 9. Current Regulator

XX = 2 digits of type number indicating voltage.

The MC7800 series can be current boosted with a PNP transistor. The MJ2955 provides current to 5.0 A. Resistor R in conjunction with the V BE 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 V BE of the pass transistor.

Figure 11. Current Boost Regulator

VO = 7.0 V to 20 V

VIN = V

O

≥

2.0 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 2.0 V greater than the regulator voltage.

Figure 10. Adjustable Output Regulator

XX = 2 digits of type number indicating voltage.

The circuit of Figure 11 can be modified to provide supply protection against short circuits by adding a short circuit sense resistor, R SC , and an additional PNP transistor. The current sensing PNP must be able to handle the short circuit current of the three-terminal regulator. Therefore, a four-ampere plastic power transistor is specified.

Figure 12. Short Circuit Protection

Figure 13. Worst Case Power Dissipation versus Ambient Temperature (Case 221A)

Figure 14. Input Output Differential as a Function of Junction Temperature (MC78XXC, AC, B)

Figure 15. D 2 PAK Thermal Resistance and Maximum Power Dissipation versus P.C.B. Copper Length

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Figure 16. DPAK Thermal Resistance and Maximum Power Dissipation versus P.C.B. Copper Length

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Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality should not be assumed, damage may occur and reliability may be affected.

*This device series contains ESD protection and exceeds the following tests: Human Body Model 2000 V per MIL_STD_883, Method 3015. Machine Model Method 200 V.

TO -220 T SUFFIX CASE 221AB

Heatsink surface connected to Pin 2.

D 2 PAK - 3 D2T SUFFIX CASE 936

Pin 1. Input

1. Ground

2. Output

Heatsink surface (shown as terminal 4 in case outline drawing) is connected to Pin 2.

DPAK - 3 DT SUFFIX CASE 369C