LT1120A Micropower Regulator with Comparator and Shutdown U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 20µA Supply Current 8-Lead SOIC 125mA Output Current 2.5V Reference Reference Output Sources 4mA and Sinks 4mA Open Collector Comparator Sinks 10mA Logic Shutdown 0.2V Dropout Voltage Thermal Limiting The LT1120A is a combination micropower positive regulator and free collector comparator on a single monolithic chip. With only 20µA supply current, the LT1120A can supply over 125mA of output current. Input voltage range is from 4.5V to 36V and dropout voltage is 0.6V at 125mA. Dropout voltage decreases with lower load currents. Also included on the chip is a class B output 2.5V reference that can either source or sink current. This allows it to be used as a supply splitter or auxiliary output. A shutdown pin allows logic shutdown of the output. U APPLICATIONS ■ ■ ■ ■ Battery Systems Battery Backup System Portable Terminals Portable Instruments Memory Keep Alive U ■ The comparator can be used for system or battery monitoring. For example, the comparator can be used to warn of low system voltage. Frequency compensation of the comparator for amplifier applications can be obtained by adding external output capacitance. TYPICAL APPLICATION VOUT 4 LT1120A + GND 10µF 3 5V 0.001µF 1 1M + FB 2 25µF 1M SHUTDOWN 1.00 10 0.10 1 SUPPLY CURRENT (mA) 5 V IN VIN > 5.2V IQ = 20µA Dropout Voltage and Supply Current DROPOUT VOLTAGE (V) 5V Regulator 1120A TA01 0.01 0.1 1 10 100 OUTPUT CURRENT (mA) 0.1 1000 1120A TA02 1 LT1120A W U U W W W Input Voltage ........................................................... 36V NPN Collector Voltage ............................................. 36V Output Short-Circuit Duration .......................... Indefinite Power Dissipation............................... Internally Limited Operating Temperature Range LT1120AC .............................................. 0°C to 100°C Storage Temperature Range LT1120AC .......................................... –65°C to 150°C U ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION ORDER PART NUMBER TOP VIEW GND 1 8 –INPUT FEEDBACK 2 7 COMP OUT SHUTDOWN 3 6 REF VOUT 4 5 VIN LT1120A N8 PACKAGE 8-LEAD PLASTIC DIP LT1120ACN8 LT1120ACS8 S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SOIC 1120A POI01 TJMAX = 110°C, θJA = 130°C/ W (N) TJMAX = 110°C, θJA = 190°C/ W (S) 1120A Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS PARAMETER Reference Reference Voltage Line Regulation Load Regulation Output Source Current Output Sink Current Temperature Stability Regulator Supply Current Output Current Load Regulation Line Regulation Dropout Voltage Feedback Sense Voltage Shutdown Pin Voltage Shutdown Pin Current Feedback Bias Current Minimum Load Current Short Circuit Current Comparator Offset Voltage Bias Current Gain Power Supply Rejection Output Sink Current Saturation Voltage Input Voltage Range Response Time Leakage Current 2 TJ = 25°C CONDITIONS MIN 4.5V ≤ VIN ≤ 36V 4.5V ≤ VIN ≤ 36V –2.0mA ≤ IREF ≤ 2mA, VIN = 12V VIN = 5V VIN = 5V 2.46 VIN = 6V, IOUT ≤ 100µA VIN = 36V, IOUT ≤ 100µA VIN = 12V, IOUT = 125mA (VIN – VOUT) ≥ 1V, VIN ≥ 6V (VIN – VOUT) ≥ 1V, VIN ≥ 6V 6V ≤ VIN ≤ 36V IOUT = 100µA IOUT = 125mA VIN = 12V Normal VOUT ≤ 0.5V Shutdown VIN = 1.4V 2 2 MAX UNITS 2.50 2.54 0.015 0.6 V %/V % mA mA % 20 30 11 25 40 20 0.2 0.01 0.02 0.40 2.5 0.5 0.015 0.05 0.65 2.56 0.4 µA µA mA mA % %/V V V V V V µA nA µA mA 0.01 0.3 4 4 1 125 2.44 2.2 VIN = 36V VIN = 36V VIN = 36V VIN = 36V ∆VOUT = 29V, RL = 20k 4.5V ≤ VS ≤ 36V VIN = 4.5V IOUT = 1mA TYP 2000 80 10 1.4 10 15 1 250 3 15 10000 96 18 0.4 0 40 5 400 7 40 0.6 VIN – 1 5 VIN = 36V, V(Pin 7) = 36V 2 mV nA V/V dB mA V V µs µA LT1120A ELECTRICAL CHARACTERISTICS PARAMETER Reference Reference Voltage Line Regulation Load Regulation Output Source Current Output Sink Current Regulator Supply Current CONDITIONS Output Current Load Regulation Line Regulation Dropout Voltage Feedback Sense Voltage Feedback Bias Current Minimum Load Current Short Circuit Current Comparator Offset Voltage Bias Current Gain Output Sink Current (Note 1) Leakage Current 4.5V ≤ VIN ≤ 36V 4.5V ≤ VIN ≤ 36V –2.0mA ≤ IREF ≤ 2mA, VIN = 12V VIN = 5V VIN = 5V ● VIN = 6V, IOUT ≤ 100µA VIN = 36V, IOUT ≤ 100µA VIN = 12V, IOUT = 125mA (VIN – VOUT) ≥ 1V, VIN ≥ 6V (VIN – VOUT) ≥ 1V, VIN ≥ 6V 6V ≤ VIN ≤ 36V IOUT = 100µA IOUT = 125mA VIN = 12V ● ● ● MIN TYP MAX UNITS 2.40 2.50 0.01 0.4 2.55 0.02 0.8 V %/V % mA mA 30 40 11 40 50 20 µA µA mA mA % %/V V V V nA µA mA ● ● ● ● ● 2 2 125 240 1 0.02 0.06 0.85 2.57 50 50 400 15 10 60 ● ● ● ● ● 2.38 2.5 ● VIN = 36V VIN = 36V ● VIN = 36V VIN = 36V ∆VOUT = 29V, RL = 20k VIN = 4.5V VIN = 36V, V(Pin 7) = 36V ● ● ● ● ● 1000 5 mV nA V/V mA µA 10 8 ● The ● denotes specifications which apply over the operating temperature range. Note 1: For TA ≤ –40°C output sink current drops to 2.5mA. U W TYPICAL PERFORMANCE CHARACTERISTICS Regulator Load Regulation PRE-LOAD = 100 µA Supply Current Regulator Short-Circuit Current 350 100 T J = –55°C T J = 25°C 0.1 0 T J = 125°C –0.1 SHORT-CIRCUIT CURRENT (mA) 0.2 SUPPLY CURRENT (mA) OUTPUT VOLTAGE CHANGE (%) 0.3 10 1 0.1 –0.2 –0.3 0.1 1 10 100 OUTPUT CURRENT (mA) 1000 1120A G01 0.01 0.1 1 1000 10 100 REGULATOR OUTPUT CURRENT (mA) 1120A G02 300 250 200 150 100 50 0 –50 –10 110 30 70 TEMPERATURE (°C) 150 1120A G03 3 LT1120A U W TYPICAL PERFORMANCE CHARACTERISTICS 70 ∆VOUT = 100mV 0.1 RIPPLE REJECTION (dB) 65 10 0.01 0.1 1 70 10 100 1 1000 REGULATOR OUTPUT CURRENT (mA) 55 I OUT = 10mA 50 I OUT = 1mA 45 VIN = 10VDC, 1Vp-p VOUT = 5V COUT = 10µF 40 30 80 90 Supply Current SUPPLY CURRENT (mA) I OUT = 10mA 1 I OUT = 10mA 0.1 I OUT = 1mA VOUT = 5V 0.01 REFERENCE VOLTAGE CHANGE (mV) 4 I OUT = 100mA I OUT = 1mA 0.01 5 1 10 25 15 20 REGULATOR INPUT-OUTPUT DIFFERENTIAL (V) TJ = –55°C 25 20 15 TJ = 25°C 10 5 0 0.1 TJ = 125°C 10 100 1 1000 REGULATOR OUTPUT CURRENT (mA) 1120A G10 1 0 –1 –2 –3 –1.0 –0.5 0.5 1.0 0 REFERENCE OUTPUT CURRENT (mA) 1.5 1120A G09 Regulator Thermal Regulation Turn-On Characteristic 0.1 5.5 VIN = 15V VOUT = 5V VOUT = 5V 5.0 NO LOAD 0 OUTPUT VOLTAGE (V) 30 OUTPUT CURRENT (mA) 35 2 1120A G08 OUTPUT VOLTAGE CHANGE (%) Feedback Pin Current 40 3 –4 –1.5 0.1 0 0.2 0.6 0.3 0.5 0.4 REGULATOR INPUT-OUTPUT DIFFERENTIAL (V) 1120A G07 4 Reference Regulation Supply Current at Dropout I OUT = 100mA 0.1 100k 1120A G06 10 1 100 10k 1k RIPPLE FREQUENCY (Hz) 10 100 110 120 130 140 150 TEMPERATURE (°C) 1120A G05 10 SUPPLY CURRENT (mA) I OUT = 100mA 60 35 1120A G04 FEEDBACK PIN CURRENT (nA) Regulator Ripple Rejection Regulator Minimum Load Current 100 MINIMUM LOAD CURRENT (µA) REGULATOR INPUT-OUTPUT DIFFERENTIAL (V) Dropout Voltage 1 –0.1 50 4.5 4.0 RL = 500Ω 3.5 3.0 2.5 2.0 0 0 20 40 60 80 100 120 140 160 180 TIME (ms) 1120A G11 RL = 50Ω 0 0 1 2 3 4 5 6 INPUT VOLTAGE (V) 7 8 1120A G12 LT1120A U U U PIN FUNCTIONS Pin 1 (Ground). Pin 5 (Input Supply): Bypass with 10µF cap. Must always be more positive than ground. Pin 2 (Feedback): This is the feedback point of the regulator. When operating, it is nominally at 2.5V. Optimum source resistance is 200k to 500k. The feedback pin should not be driven below ground or more positive than 5V. Pin 6 (Reference): 2.5V can source or sink current. May be shorted to ground or up to 5V. Voltages in excess of 5V can damage the device. Pin 7 (Comparator Output): May be connected to any voltage from ground to 36V more positive than ground (operates above VIN). Short circuit protected. Pin 3 (Shutdown): A logic 1 shuts off main regulator. Caution: noise or leakage into the shutdown pin can affect output voltage. Pin 8 (Comparator Input): Inverting comparator input. Pin 4 (Regulator Output): Main output, requires 10µF output capacitor. Can be shorted to VIN or ground without damaging device. W BLOCK DIAGRAM REFERENCE 6 VIN 5 COMPARATOR OUT 7 100k + – REF 2.5V 4 VOUT 2 FEEDBACK 3 SHUTDOWN 1 GROUND 120k 8 –INPUT 1120A BD01 U W U U APPLICATIONS INFORMATION The LT1120A is especially suited for micropower system applications. For example, the comparator section of the LT1120A may be used as a battery checker to provide an indication of low battery. Another type of system application for the LT1120A would be to generate the equivalent of split supplies off of a single power input. The regulator section provides regulated output voltage and the reference, which can both source and sink current is then an artificial system ground providing a split supply for the system. For many applications the comparator can be frequency compensated to operate as an amplifier. Compensation values for various gains are given in the data sheet. The comparator gain is purposely low to make it easier to frequency compensate as an amplifier. The NPN output is capable of sinking 10mA and can drive loads connected to voltages in excess of the positive power supply. This is useful for driving switches or linear regulators off of a higher input voltage. 5 LT1120A U U W U APPLICATIONS INFORMATION Reference Internal to the LT1120A is a 2.5V trimmed class B output reference. The reference was designed to be able to source or sink current so it could be used in supply splitting applications as well as a general purpose reference for external circuitry. The design of the reference allows it to source and sink typically 4mA. The available source and sink current decreases as temperature increases. It is sometimes desirable to decrease the AC output impedance by placing an output capacitor on Pin 6. The reference in the LT1120A becomes unstable with large capacitive loads placed directly on it. When using an output capacitor, about 20Ω should be used to isolate the capacitor from the reference pin. This 20Ω resistor can be placed directly in series with the capacitor or alternatively the reference line can have 20Ω placed in series with it and then a capacitor to ground. This is shown in Figure 1. Other than placing large capacitive loads on the reference, no other precautions are necessary and the reference is stable with nominal stray capacitances. REF REF 6 6 OUTPUT 20Ω + 10µF OR 20Ω + OUTPUT 10µF 1120A AI01 Figure 1. Bypassing Reference Overload Protection The main regulator in the LT1120A is current limited at approximately 250mA. The current limit is stable with both input voltage and temperature. Like most other IC regulators, a minimum load is required on the output of the LT1120A to maintain regulation. For 6 most standard regulators this is normally specified at 5mA. Of course, for a micropower regulator this would be a tremendously large current. The output current must be large enough to absorb all the leakage current of the pass transistor at the maximum operating temperature. It also affects the transient response; low output currents have long recovery times from load transients. At high operating temperatures the minimum load current increases and having too low of a load current may cause the output to go unregulated. Devices are tested for minimum load current at high temperature. The output voltage setting resistors to the feedback terminal can usually be used to provide the minimum load current. Frequency Compensation The LT1120A is frequency compensated by a dominant pole on the output. An output capacitor of 10µF is usually large enough to provide good stability. Increasing the output capacitor above 10µF further improves stability. In order to ensure stability, a feedback capacitor is needed between the output pin and the feedback pin. This is because stray capacitance can form another pole with the large value of feedback resistors used with the LT1120A. Also, a feedback capacitor minimizes noise pickup and improves ripple rejection. With the large dynamic operating range of the output current, 10000:1, frequency response changes widely. Low AC impedance capacitors are needed to insure stability. While solid tantalum are best, aluminum electrolytics can be used but larger capacitor values may be needed. LT1120A U TYPICAL APPLICATIONS Regulator with Output Voltage Monitor 5 VIN 5V OUTPUT LOGIC + – 500k 0.001µF + FEEDBACK LOGIC OUTPUT 98k 10µF 8 LT1120A 7 OUTPUT 5V 4 REF 6 2k 2 100k GND 1 1120A TA03 LOGIC OUTPUT GOES LOW WHEN VOUT DROPS BY 100mV Compensating the Comparator as an Op Amp VREF 6 0.5Ω* 2.2k 50µA + R2 VIN MJE2955 7 – IN Current Limited 1 Amp Regulator 1M + 0.22µF C2 R1 33Ω 100Ω 10k C1 0.1µF 0.047µF 0.002µF 1M VOUT 5V AT 1A 220µF† VOUT 4 R1 C1 AV –1 –10 –100 2N3906* 5 VIN AT AV = 100, SLEW RATE = +0.05V/µs – 6V/µs LT1120A FB 2 GND 1 C2 R2 0.001µF 1M – 100k – 10k 270Ω 100k 1120A TA04 * SETS CURRENT LIMIT BUT INCREASES DROPOUT VOLTAGE BY 0.5V. † MUST HAVE LOW ESR. SEVERAL 100µF CAPACITORS CAN BE PARALLELED. 1120A TA06 Battery Backup Regulator VOUT 5V 5 BATTERY INPUT VOUT VIN + LT1120A GND 1 0.001µF FB 1M 2 VIN VOUT 5 LT1120A 10µF 2 50k INTERNAL PARASITIC DIODES OF LT1120A VIN 4 4 FB MAIN POWER INPUT GND 1 1M 1120A TA05 VOUT Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 7 LT1120A U PACKAGE DESCRIPTION Dimension in inches (millimeters) unless otherwise noted. N8 Package 8-Lead Plastic DIP 0.400 (10.160) MAX 8 7 6 5 0.250 ± 0.010 (6.350 ± 0.254) 1 0.300 – 0.320 (7.620 – 8.128) +0.635 –0.381 4 0.130 ± 0.005 (3.302 ± 0.127) 0.065 (1.651) TYP +0.025 0.325 –0.015 8.255 3 0.045 – 0.065 (1.143 – 1.651) 0.009 – 0.015 (0.229 – 0.381) ( 2 0.125 (3.175) MIN 0.045 ± 0.015 (1.143 ± 0.381) ) 0.020 (0.508) MIN 0.018 ± 0.003 (0.457 ± 0.076) 0.100 ± 0.010 (2.540 ± 0.254) N8 0392 S8 Package 8-Lead Plastic SOIC (Narrow) 0.189 – 0.197 (4.801 – 5.004) 8 7 6 5 0.228 – 0.244 (5.791 – 6.197) 0.150 – 0.157 (3.810 – 3.988) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 8 0.016 – 0.050 0.406 – 1.270 Linear Technology Corporation 3 4 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 0.008 – 0.010 (0.203 – 0.254) 0°– 8° TYP 2 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) BSC SO8 0392 LT/GP 0494 10K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1994