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LM350

3-Terminal 3A Positive Adjustable Voltage Regulator
Features
• • • • • • • Output adjustable between 1.2V and 33V Guaranteed 3A output current Internal thermal overload protection Load regulation (Typ: 0.1%) Line regulation (Typ: 0.015%/V) Internal short-circuit current limit Output transistor safe-area compensation

Description
The LM350 is an adjustable3-terminal positive voltage regulator capable of supplying in excess of 3.0 A over an output voltage range of 1.2V to 33 V
TO-220

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1. Adj 2. Output 3. Input

Internal Block Diagram

Rev. 1.0.0
©2001 Fairchild Semiconductor Corporation

LM350

Absolute Maximum Ratings
Parameter Input-Output Voltage Differential Lead Temperature (Soldering, 10sec) Power Dissipation OperatingTemperature Range Storage Temperature Range Symbol V I - VO TLEAD PD TOPR TSTG Value 35 300 Internally limited 0 ~ +125 -65 ~ +150 Unit VDC °C °C °C

Electrical Characteristics
(VI-VO=5V, IO=1.5A, TJ=0°C to + 125°C; PD ≤ PDMAX, unless otherwise specified) Parameter Line Regulation (Note1) Load Regulation (Note1) Adjustment Pin Current Adjustment Pin Current Change Thermal Regulation Reference VoltageLine Regulation Load Regulation Temperature Stability Maximum Output Current Minimum Load Current RMS Noise, %of VOUT Ripple Rejection Long-Term Stability Symbol Rline Rload IADJ ∆IADJ REGT VREF Rline Rload STT Io(MAX) IL(MIN) VN RR ST Conditions TA = +25°C, 3V ≤ VI -VO ≤ 35V TA = +25 °C, 3V ≤ VI -VO ≤ 35V VO ≤ 5V VO ≥ 5V 3V ≤ VI -VO ≤ 35V, 10mA ≤ Io ≤ 3A, PD ≤ PMAX Pulse = 20ms, TA =+ 25°C 3V ≤VI -VO ≤ 35V, 10mA ≤I O≤ 3A,PD ≤ 30W 3.0V ≤ VI -VO ≤ 35V 10mA ≤ I O ≤ 3.0A VO ≤ 5.0V VO ≥ 5.0V TJ = 0°C to + 125°C VI -VO ≤ 10V, PD ≤ PMAX VI -VO = 30V, PD ≤ PMAX,TA = +25°C VI -VO = 35V 10Hz ≤ f ≤ 10KHz, TA= +25 °C VO = 10V, f = 120Hz, CADJ = 0 CADJ = 10µF TJ =+125 °C Min. 1.2 3.0 0.25 Typ. Max. Unit %/V mV % µA µA %/W V %/W mV % % A A mA %/Vo dB dB 1 %/ 1000HR

0.015 0.03 5 0.1 50 0.2 0.0021.25 0.02 20 0.3 1.0 4.5 1.0 3.5 0.003 65 80 0.3 25 0.5 100 5.0 1.30 0.07 70 1.5 10 -

66 -

Note: 1. Regulation is measured at constant junction temperature. Changes in output voltage due to heating effects must be taken into account separately. Pulse testing with low duty cycle is used.

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LM350

Typical Perfomance Characteristics

Figure 1. Load Regulation

Figure 2. Current LimitFigure 3. Adjustment Pin Current

Figure 4. Dropout Voltage

Figure 5. Temperature Stability

Figure 6. Minimum Load Current

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LM350

Typical Perfomance Characteristics (continued)

Figure 7. Ripple Rejection vs Vo

Figure 8. Ripple Rejection vs Io

Figure 9. Ripple Rejection vs Frequency

Figure 10. Output Impedance

Figure 11. Line Transient Response

Figure 12.Load Transient Response

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LM350

Typical Application

Input

LM350

Output

Figure 13.

CI : CI is required if the regulator is located an appreciable distance from power supply filter. CO : Output capacitors in the range of 1µF to 100µF of aluminum or tantalum electronic are commonly used to provide improved output impedance and rejection of transients. In operation, the LM350develops a nominal 1.25V reference voltage, VREF, between the output and adjustment terminal. The reference voltage is impressed across program resistor R1 and, since the voltage is constant, a constant current I1 then flows through the output set resistor R2, giving an output voltage of VO = 1.25V(1+R2/R1) + IADJ R2 Since IADJ current (less than 100µF) from the adjustment terminal represents anerror term, the LM350 was designed to minimize IADJ and make it very constant with line and load changes. To do this, all quiescent operating current is returned to the output establishing a minimum load current requirement. If there is insufficient load on the output, the output voltage will rise. Since the LM350 is a floating regulator, it is only the voltage differential across the circuit which...