LT1185 - Low Dropout Regulator

1 LT1185 . Low Dropout Regulator FEATURES. Low Resistance Pass Transistor: The LT1185 uses a saturation-limited NPN transistor as Dropout voltage : at 3A the pass element. This device gives the linear Dropout 1% Reference voltage characteristics of a FET pass element with significantly Accurate Programmable Current Limit less die area. High efficiency is maintained by using special Shutdown Capability anti-saturation circuitry that adjusts base drive to track Internal Reference Available load current. The on resistance is typically . Full Remote Sense Accurate current limit is programmed with a single 1/8W. Low Quiescent Current: external resistor, with a range of zero to three amperes. A. Good High Frequency Ripple Rejection second, fixed internal limit circuit prevents destructive Available in 5-Lead TO-220 and DD Packages currents if the programming current is accidentally over- U ranged.

2 Shutdown of the Regulator output is guaranteed DESCRIPTIO when the program current is less than 1 A, allowing external logic control of output voltage . The LT 1185 is a 3A low Dropout Regulator with adjustable current limit and remote sense capability. It can be used as The LT1185 has all the protection features of previous a positive output Regulator with floating input or as a LTC regulators , including power limiting and thermal standard negative Regulator with grounded input. The shutdown. output voltage range is to 25V, with 1% accuracy on , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. the internal reference voltage . U. TYPICAL APPLICATIO. 5V, 3A Regulator with Current Limit Dropout voltage + + + 2 F RLIM* TANT VIN 6V TO 16V REF GND + VOUT. VIN VOUT (V).

3 2 F FB 5V AT 3A TJ = 25 C. TANT. TJ = 125 C. VIN LT1185 VOUT LT1185 TA01 TJ = 55 C. *CURRENT LIMIT = 15k/RLIM = 0. 0 1 2 3 4. LOAD CURRENT (A). LT1185 TA02. 1185ff 1. LT1185 . W W W U (Note 1). ABSOLUTE AXI U RATI GS. Input voltage .. 35V Operating Junction Temperature Range*. Input-Output Differential .. 30V Control Section FB voltage .. 7V LT1185C .. 0 C to 125 C. REF voltage .. 7V LT1185I .. 40 C to 125 C. Output voltage .. 30V LT1185M (OBSOLETE) .. 55 C to 150 C. Output Reverse voltage .. 2V Power Transistor Section Operating Ambient Temperature Range LT1185C .. 0 C to 150 C. LT1185C .. 0 C to 70 C LT1185I .. 40 C to 150 C. LT1185I .. 40 C to 85 C LT1185M (OBSOLETE) .. 55 C to 175 C. LT1185M (OBSOLETE) .. 55 C to 125 C Storage Temperature Range .. 65 C to 150 C. *See Application Section for details on calculating Operation Junction Temperature Lead Temperature (Soldering, 10 sec).

4 300 C. U W U. PACKAGE/ORDER I FOR ATIO. BOTTOM VIEW. GND FB FRONT VIEW FRONT VIEW. 5 REF 5 REF. 1. 2 4 VOUT 4 VOUT. VIN (CASE) TAB. 3 IS 3 VIN 3 VIN. 4 VIN. 2 FB 2 FB. VOUT 1 GND 1 GND. REF. Q PACKAGE TAB IS VIN T PACKAGE. K PACKAGE. 5-LEAD PLASTIC DD 5-LEAD PLASTIC TO-220. 4-LEAD TO-3 METAL CAN. JC MAX = C/ W, JA = 35 C/W TJMAX = 150 C, JA = 30 C/W JC MAX = C/ W, JA = 50 C/W. OBSOLETE PACKAGE. ORDER PART ORDER PART LT1185CQ ORDER PART LT1185CT. LT1185MK. NUMBER NUMBER LT1185IQ NUMBER LT1185IT. Order Options Tape and Reel: Add #TR. Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF. Lead Free Part Marking: Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS. The denotes specifications which apply over the operating temperature range, otherwise specifications are at TA = 25 C. Adjustable version, VIN = , VOUT = 5V, IOUT = 1mA, RLIM = , unless otherwise noted.

5 PARAMETER CONDITIONS MIN TYP MAX UNITS. Reference voltage (At FB Pin) V. Reference voltage Tolerance (At FB Pin) (Note 2) VIN VOUT = 5V, VOUT = VREF 1 %. 1mA IOUT 3A 1 %. VIN VOUT = to VIN = 30V. P 25W (Note 6), VOUT = 5V. TMIN TJ TMAX (Note 9). Feedback Pin Bias Current VOUT = VREF 2 A. Droput voltage (Note 3) IOUT = , VOUT = 5V V. IOUT = 3A, VOUT = 5V V. 1185ff 2. LT1185 . ELECTRICAL CHARACTERISTICS. The denotes specifications which apply over the operating temperature range, otherwise specifications are at TA = 25 C. Adjustable version, VIN = , VOUT = 5V, IOUT = 1mA, RLIM = , unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS. Load Regulation (Note 7) IOUT = 5mA to 3A %. VIN VOUT = to 10V, VOUT = 5V. Line Regulation (Note 7) VIN VOUT = 1V to 20V, VOUT = 5V %/V. Minimum Input voltage IOUT = 1A (Note 4), VOUT = VREF V. IOUT = 3A V. Internal Current Limit (See Graph for VIN VOUT 10V A.)

6 Guaranteed Curve) (Note 12) A. VIN VOUT = 15V A. VIN VOUT = 20V A. VIN VOUT = 30V A. External Current Limit 5k RLIM 15k, VOUT = 1V 15k A . Programming Constant (Note 11). External Current Limit Error 1A ILIM 3A ILIM ILIM + A. RLIM = 15k A/ILIM ILIM ILIM + A. Quiescent Supply Current IOUT = 5mA, VOUT = VREF mA. 4V VIN 25V (Note 5). Supply Current Change with Load VIN VOUT = VSAT (Note 10) 25 40 mA/A. VIN VOUT 2V 10 25 mA/A. REF Pin Shutoff Current 2 7 A. Thermal Regulation (See Applications VIN VOUT = 10V %/W. Information) IOUT = 5mA to 2A. Reference voltage Temperature Coefficient (Note 8) %/ C. Thermal Resistance Junction to Case TO-3 Control Area 1 C/W. Power Transistor 3 C/W. TO-220 Control Area 1 C/W. Power Transistor 3 C/W. Note 1: Stresses beyond those listed under Absolute Maximum Ratings Note 6: The 25W power level is guaranteed for an input-output voltage of may cause permanent damage to the device.

7 Exposure to any Absolute to 17V. At lower voltages the 3A limit applies, and at higher voltages Maximum Rating condition for extended periods may affect device the internal power limiting may restrict Regulator power below 25W. See reliability and lifetime. graphs. Note 2: Reference voltage is guaranteed both at nominal conditions (no Note 7: Line and load regulation are measured on a pulse basis with a load, 25 C) and at worst-case conditions of load, line, power and pulse width of 2ms, to minimize heating. DC regulation will be affected temperature. An intermediate value can be calculated by adding the effects by thermal regulation and temperature coefficient of the reference. See of these variables in the actual application. See the Applications Applications Information section for details. Information section of this data sheet. Note 8: Guaranteed by design and correlation to other tests, but not Note 3: Dropout voltage is tested by reducing input voltage until the tested.

8 Output drops 1% below its nominal value. Tests are done at and 3A. Note 9: TJMIN = 0 C for the LT1185C, 40 C for LT1185I, and 55 C for The power transistor looks basically like a pure resistance in this range so the LT1185M. Power transistor area and control circuit area have different that minimum differential at any intermediate current can be calculated by maximum junction temperatures. Control area limits are TJMAX = 125 C for interpolation; VDROPOUT = + IOUT. For load current less than the LT1185C and LT1185I and 150 C for the LT1185M. Power area limits , see graph. are 150 C for LT1185C and LT1185I and 175 C for LT1185M. Note 4: Minimum input voltage is limited by base emitter voltage drive Note 10: VSAT is the maximum specified Dropout voltage ;. of the power transistor section, not saturation as measured in Note 3. For + IOUT. output voltages below 4V, minimum input voltage specification may limit Note 11: Current limit is programmed with a resistor from REF pin to GND.

9 Dropout voltage before transistor saturation limitation. pin. The value is 15k/ILIM. Note 5: Supply current is measured on the ground pin, and does not Note 12: For VIN VOUT = ; VIN = 5V, VOUT = VOUT = 1V for all include load current, RLIM, or output divider current. other current limit tests. 1185ff 3. LT1185 . U W. TYPICAL PERFOR A CE CHARACTERISTICS. Feedback Pin voltage Internal Current Limit Quiescent Ground Pin Current* Temperature Drift 5 12 ILOAD = 0. TJ = 25 C 10. GROUND PIN CURRENT (mA). 4. GUARANTEED OUTPUT CURRNT (A). LIMIT *DOES NOT INCLUDE REF CURRENT. 8. OR OUTPUT DIVIDER CURRENT. voltage (V). 3. 6 TYPICAL. 2 4. VOUT = 5V 1 GUARANTEED. LIMIT 2. TEST POINTS. 0 0 0 5 10 15 20 25 30 0 5 10 15 20 25 30 35 50 25 0 25 50 75 100 125 150. INPUT-OUTPUT DIFFERENTIAL (V) INPUT voltage (V) JUNCTION TEMPERATURE ( C). LT1185 TPC02 LT1185 TPC03. LT1185 TPC01.

10 Ground Pin Current Ripple Rejection vs Frequency 160 100. TJ = 25 C. 140. 80. 120. RATIO VOUT/VIN (dB). ALL OUTPUT. CURRENT (mA). 100 VOLTAGES. 60 WITH F. Regulator JUST AT ACROSS R2. 80. Dropout POINT. 60 40. VOUT = 5V. VIN VOUT = 40. VIN VOUT = 5V 20. 20. 0 0. 0 1 2 3 4 100 1k 10k 100k 1M. LOAD CURRENT (A) FREQUENCY (Hz). LT1185 TPC04 LT1185 TPC05. Load Transient Response Output Impedance 10. OUTPUT IMPEDANCE IS. COUT = F, ESR = 1 SET BY OUTPUT CAPACITOR. ESR IN THIS REGION. 1. 100mV. IMPEDANCE ( ). COUT = F, ESR = 2 . VOUT = 5V. IOUT = 1A. ILOAD tr,f 100ns VOUT = 5V. IOUT = 1A. COUT = F. 0 2 4 6 8 10 12 14 16 1k 10k 100k 1M. TIME ( s) FREQUENCY (Hz). LT1183 TPC07. LT1185 TPC06. 1185ff 4. LT1185 . U U W U. APPLICATIO S I FOR ATIO. Block Diagram A simplified block diagram of the LT1185 is shown in conditions, resulting in very high supply current when the Figure 1.