19-3894; Rev 3; 10/94 +5V/Programmable Low-Dropout Voltage Regulator ________________________Applications ____________________________Features ♦ 350mV Max Dropout at 200mA ♦ 250mA Output Current ♦ Normal Mode: 20µA Typ Quiescent Current Shutdown Mode: 0.2µA Typ Quiescent Current ♦ Low-Battery Detector ♦ Fixed +5V (Min Component Count) or Adjustable Output ♦ +3.5V to +16.5V Input ♦ Dropout Detector Output ♦ 10µF Output Capacitor ______________Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX667CPA 0°C to +70°C 8 Plastic DIP MAX667CSA 0°C to +70°C 8 SO Battery-Powered Devices MAX667C/D 0°C to +70°C Dice* Pagers and Radio Control Receivers MAX667EPA -40°C to +85°C MAX667ESA -40°C to +85°C 8 SO MAX667MJA -55°C to +125°C 8 CERDIP Portable Instruments 8 Plastic DIP Solar-Powered Instruments * Contact factory for dice specifications. __________Typical Operating Circuit __________________Pin Configuration TOP VIEW IN +5V OUT OUT C1 10µF +6.3V BATTERY MAX667 SET TM Dual GND SHDN DD 1 8 IN OUT 2 7 LBO LBI 3 6 SET GND 4 5 SHDN MAX667 DIP/SO Mode is a trademark of Maxim Integrated Products. ________________________________________________________________ Maxim Integrated Products Call toll free 1-800-998-8800 for free samples or literature. 1 MAX667 _______________General Description The MAX667 low-dropout, positive, linear voltage regulator supplies up to 250mA of output current. With no load, it has a typical quiescent current of 20µA. At 200mA of output current, the input/output voltage differential is typically 150mV. Other features include a lowvoltage detector to indicate power failure, as well as early-warning and low-dropout detectors to indicate an imminent loss of output voltage regulation. A shutdown control disables the output and puts the circuit into a low quiescent-current mode. The MAX667 employs Dual Mode™ operation. One mode uses internally trimmed feedback resistors to produce +5V. In the other mode, the output may be varied from +1.3V to +16V by connecting two external resistors. The MAX667 is a pin-compatible upgrade to the MAX666 in most applications where the input voltages are above +3.5V. Choose the MAX667 when high output currents and/or low dropout voltages are desired, as well as for improved performance at higher temperatures. MAX667 +5V/Programmable Low-Dropout Voltage Regulator ABSOLUTE MAXIMUM RATINGS Input Supply Voltage ...........................................................+18V Output Short Circuited to Ground.........................................1sec LBO Output Sink Current ....................................................50mA LBO Output Voltage ...............................................GND to VOUT SHDN Input Voltage ....................................-0.3V to (VIN + 0.3V) Input Voltages LBI, SET................................-0.3V to (VIN - 1.0V) Continuous Power Dissipation Plastic DIP (derate 9.09mW/°C above +70°C) ............727mW SO (derate 5.88mW/°C above +70°C) .........................471mW CERDIP (derate 8.00mW/°C above +70°C) .................640mW Operating Temperature Ranges MAX667C_A........................................................0°C to +70°C MAX667E_A .....................................................-40°C to +85°C MAX667MJA ..................................................-55°C to +125°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (GND = 0V, VIN = +9V, VOUT = +5V, C1 = 10µF, unless otherwise noted.) PARAMETER Input Voltage Output Voltage Maximum Output Current SYMBOL CONDITIONS MIN TA = +25°C TA = TMIN to TMAX TYP MAX MIN TYP MAX VIN VOUT IOUT VSET = 0V, VIN = 6V, IOUT = 10mA, TA = -40°C to +85°C VSET = 0V, VIN = 6V, IOUT = 10mA, TA = -55°C to +125°C VIN = 6V, 4.5V < VOUT < 5.5V 3.5 16.5 5 4.8 5.2 5 4.75 5.25 UNITS V V 250 VSHDN = 2V 250 mA 0.2 1 2 IOUT = 0µA 20 25 35 IOUT = 100µA 20 30 50 5 5 150 50 15 60 250 100 20 75 350 250 mA Load Regulation IOUT = 200mA IOUT = 100µA IOUT = 200mA IOUT = 10mA to 200mA Line Regulation VIN = 6V to 10V, IOUT = 10mA 5 10 15 mV Quiescent Current IQ Dropout Voltage (Note1) VSHDN = 0V, VSET = 0V SET Reference Voltage VSET 1.225 SET Input Leakage Current ISET VSET = 1.5V 0.01 Output Leakage Current IOUT VSHDN = 2V 0.1 Short-Circuit Current Low-Battery Detector Reference Voltage Low-Battery Detector Input Leakage Current Low-Battery Detector Output Voltage IOUT (Note 2) VLBI ILBI VLBO 1.20 0.01 VIN = 9V, VLBI = 2V, ILBO = 10mA SHDN Threshold VSHDN VIH VIL SHDN Leakage Current ISHDN VSHDN = 0V to VIN Dropout Detector Output Voltage VDD VSET = 0V, VSHDN = 0V, RDD = 100kΩ, IOUT = 10mA mV V ±10 ±1000 nA 1 µA 400 450 mA 1.255 V ±1000 nA 0.4 V 1.195 ±10 0.25 1.5 1.5 0.01 mV 1.25 1.225 VLBI = 1.5V µA 0.3 0.3 ±10 ±1000 VIN = 7V V nA 0.25 V VIN = 4.5V 3.5 Note 1: Dropout Voltage is VIN-VOUT when VOUT falls to 0.1V below its value at VIN = VOUT + 2V. Note 2: Short-Circuit Current is pulse tested to maintain junction temperature. Short-circuit duration is limited by package dissipation. 2 _______________________________________________________________________________________ +5V/Programmable Low-Dropout Voltage Regulator QUIESCENT CURRENT vs. LOAD CURRENT 10,000 1000 100 MAX667-Fg TOC 3 VIN = +6V 1000 5 10 DD OUTPUT CURRENT (µA) 10 QUIESCENT CURRENT (µA) MAX667-Fg TOC 1 DROPOUT VOLTAGE (mV) 100 100,000 DD OUTPUT CURRENT vs. INPUT-OUTPUT DIFFERENCE MAX667-Fg TOC 2 DROPOUT VOLTAGE vs. LOAD CURRENT 1000 20 50 100mA LOAD 100 10 1 1 1 10 100 1000 10 0.01 1 _____________________Pin Description NAME FUNCTION DD Dropout Detector Output—the collector of a PNP pass transistor. Normally an open circuit, it sources current as dropout is reached. 2 OUT Regulated Output Voltage. OUT falls to 0V when SHDN is above 1.5V. SET determines output voltage when SET is above 50mV; otherwise, it is 5V. OUT must be connected to an output filter capacitor. 3 LBI Low-Battery Detector. A CMOS input to an internal 1.255V comparator whose output is the LBO pin. 4 GND 1 5 SHDN 6 SET 7 LBO 8 IN 10 LOAD CURRENT (mA) LOAD CURRENT (mA) PIN Ground Shutdown Input. Connect to GND for normal operation (output active). Pull above 1.5V to disable OUT, LBO, and DD and to reduce quiescent current to less than 1µA. (Output) Voltage Set, CMOS Input. Connect to GND for 5V output. For other voltages, connect external resistive divider from OUT. Low-Battery Output. An open-drain Nchannel transistor that sinks current to GND when LBI is less than 1.22V. Positive Input Voltage (unregulated) 2 1 0.1 100 1000 0 50 100 150 200 250 INPUT-OUTPUT DIFFERENCE (mV) _______________Detailed Description Figure 1 shows a micropower bandgap reference, an error amplifier, a PNP pass transistor, and two comparators as the main elements of the MAX667. One comparator, C1, selects the fixed 5V or adjustable operation with an external voltage divider. The other comparator, C2, is a low-battery detector. The bandgap reference, which is trimmed to 1.22V, connects internally to one input of the error amplifier, A1. The feedback signal from the regulator output supplies the other input of A1 from either an on-chip voltage divider or two external resistors. When SET is grounded, the internal divider provides the error amplifier feedback signal for a fixed 5V output. When SET is more than 50mV above ground, the error amplifier’s input switches directly to SET while an external resistor divider from OUT determines the output voltage. A second comparator, C2, compares the LBI input to the internal reference voltage. LBO is an open-drain FET connected to GND. The low-battery threshold can also be set with a voltage divider at LBI. In addition, the MAX667 has a shutdown input (SHDN) that disables the load and the device while reducing quiescent current when it is pulled high. +5V Output Figure 2 shows the connection for a fixed 5V output. The SET input is grounded, and no external resistors are required. Figure 3 shows adjustable output operation. R1 and R2 set the output voltage. SHDN should be grounded if not used. _______________________________________________________________________________________ 3 MAX667 __________________________________________Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) MAX667 +5V/Programmable Low-Dropout Voltage Regulator IN OUT DD SHDN A1 SET LBO C2 C1 1.255V REF LBI +50mV GND MAX667 Figure 1. MAX667 Block Diagram 8 IN OUT 2 C1 10µF 8 +5V OUT 250mA MAX667 OUT IN C1 10µF 7 LBO VREF N MAX667 R3 R2 3 LBI SET GND SHDN 6 4 5 Figure 2. Fixed +5V Regulator 4 VOUT 2 R4 SET SHDN GND 5 4 6 R1 Figure 3. Adjustable Output and Low-Battery Detector _______________________________________________________________________________________ +5V/Programmable Low-Dropout Voltage Regulator Dropout Detector The minimum input-output differential, or dropout voltage, determines the regulator’s lowest usable input voltage. In battery-operated systems, this determines the useful end-of-life battery voltage. The MAX667 features very low dropout voltage (see Electrical Characteristics). In addition, the MAX667 has a dropout detector output, DD, that changes as the dropout voltage approaches its limit. DD is an open collector of a PNP transistor. The dropout voltage and the dropout detector both depend on the output current and temperature. When the input voltage is more than 300mV above the output voltage, the dropout detector will not conduct. As the differential decreases below 300mV, the DD source current increases abruptly. This current signals a warning that regulation is about to be lost. Connecting a resistor (typically 100kΩ) from DD to ground develops a voltage that can be monitored by analog circuits or changed to digital levels by a comparator. LBI may be used for this purpose. Output Capacitor As with all PNP output regulators, an output capacitor (C1, Figure 2) is required to maintain stability. 10µF is recommended. To ensure stability, the output-capacitor ESR must be sufficiently high. Figure 4 shows the minimum required output-capacitor ESR for a given temperature. Alternatively, a resistor may be added in series with the output capacitor (Figure 5); the sum of the out- 5 MAX667-Fg 4 Low-Battery Function The MAX667 contains circuitry for low-battery detection. If the voltage at LBI falls below the regulator’s internal reference (1.22V), LBO, an open-drain output, sinks current to GND. The threshold can be set to any level above the reference voltage by connecting a resistive divider to LBI based on the equation: R3 = R4 x (VBATT / VLBI - 1) where VBATT is the desired threshold of the low-battery detector, and R3 and R4 are the LBI input divider resistors. Since LBI input current is no more than 10nA, high values for R3 and R4 minimize loading. If VOUT is 5V, a 5.5V low-battery threshold can be set using 8.2MΩ for R3 and 2.4MΩ for R4. When resistor values greater than 1MΩ are used, pay special attention to PC board leakage that can introduce error at the LBI input. When the voltage at LBI is below the internal threshold, LBO sinks current to GND. A pull-up resistor of 10kΩ or more connected to OUT can be used with this pin when driving CMOS circuits. Any pull-up resistor connected to LBO should not be returned to a voltage source greater than VOUT. When LBI is above the threshold or the MAX667 is in SHDN mode, the LBO output is off. __________Applications Information 4 MINIMUM ESR (Ω) Shutdown (Standby) Mode SHDN puts the device into standby mode to conserve power. When this pin is held low, the IC operates normally. If it is driven above 1.5V, the chip shuts down. Quiescent current of the MAX667 is then reduced to less than 1µA, and OUT turns off. Note that the voltage for SHDN must never be more than 0.3V higher than VIN. 3 2 1 0 -60 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (˚C) Figure 4. Minimum Required Output-Capacitor ESR vs. Temperature _______________________________________________________________________________________ 5 MAX667 Output-Voltage Selection If SET is connected to a resistive voltage divider (Figure 3), the output voltage is set by the equation: VOUT = VSET x (R1 + R2) / R1, where VSET = 1.22V To simplify resistor selection: R2 = R1 x (VOUT / VSET - 1) Since the input bias current at SET has a maximum value of 10nA, relatively large values can be used for R1 and R2 with no loss of accuracy. 1MΩ is a typical value for R1. The VSET tolerance is less than ±25mV. This allows the output to be preset without trim pots, using only fixed resistors in most cases. However, when resistor values greater than 1MΩ are used, pay special attention to printed circuit board leakage that can introduce error at the SET input. MAX667 +5V/Programmable Low-Dropout Voltage Regulator 8 IN OUT 8 2 +5V OUT OUT IN +5V OUT MAX667 R MAX667 C1 10µF 2 R2 1M 10µF 5 SET GND 6 4 SET SHDN SHDN GND DD 4 1 6 R1 332k 5 R3 1M Figure 5. Alternative Stability Scheme Using Resistor R Figure 7. Connection for Minimum Quiescent Current Near Dropout IN OUT 2 VSHDN = 0V +5V OUT QUIESCENT CURRENT (mA) C1 10µF MAX667 DD SET GND SHDN 6 4 5 1 R1 47k MAX667-Fg 8 10 8 C2 0.1µF 8 6 4 2 0 0 1 2 3 4 5 6 INPUT VOLTAGE (V) Figure 6. Quiescent-Current Reduction Below Dropout put-capacitor ESR and this series resistance should, at minimum, meet the requirements shown in Figure 4. An upper limit to the output-capacitor ESR is important only if step changes to the load are anticipated. Higher ESR results in higher-amplitude output-voltage transients when the output current is varied. A Sanyo OS-CON capacitor, whose ESR is nearly flat over temperature (and is low to begin with), in series with the appropriate resistor ensures the best load-transient performance. A less expensive alternative is to use a tantalum capacitor in series with the resistor. 6 Figure 8. Quiescent Current Below Dropout for Circuit of Figure 2 In most cases, inexpensive aluminum-electrolytic capacitors work well with the MAX667 over their entire temperature range, having sufficient ESR to ensure stability without the need for a series resistor. The ESR of aluminium electrolytics rises, often dramatically, as temperature decreases. For surface-mount applications, certain tantalum capacitors have sufficient ESR; an example is the TAJB106K016 chip capacitor made by AVX (phone: (803) 448-9411, fax: (803) 448-1943). Battery Drain The MAX667 uses a PNP output transistor. When the input voltage falls below the desired output voltage, the _______________________________________________________________________________________ +5V/Programmable Low-Dropout Voltage Regulator TA = +50˚C LOAD CURRENT (mA) 400 CIRCUIT OF FIGURE 6 200 300 GUARANTEED 250mA 200 DIP PACKAGE DISSIPATION LIMIT 100 0 SO PACKAGE DISSIPATION LIMIT 0 1 2 3 4 5 MAX667-Fg 10 MAX667-Fg 9 CIRCUIT OF FIGURE 7 600 IGND (µA) 400 MAX667 800 6 0 VIN (V) 5 10 15 VIN-VOUT (V) Figure 9. Quiescent Current Below Dropout with Connections of Figures 6 and 7 PNP transistor is turned on fully as regulation is lost. Even with a load current of a few microamperes, the base current will be driven above 5mA. Figure 8 shows how this base current may be significant. Consequently, a mostly discharged battery can be further discharged at end-of-life. Figure 6 shows how this condition can be modified by connecting DD to SHDN with a 47kΩ resistor, R1, paralleled with a 0.1µF capacitor to GND. This modification reduces the no-load quiescent current to approximately 160µA when dropout is reached (Figure 9), but increases the dropout voltage by about 0.1V. The output voltage drops to approximately 3V once DD begins to activate SHDN, but it does not fall to zero because SHDN is only partially activated. A second alternate connection (Figure 7) further reduces quiescent current near the dropout voltage, compared to the circuit in Figure 6. The output must be set with external resistors (R1, R2), so DD lowers the output voltage as the input voltage falls by sourcing current into SET via R3. Quiescent current remains low for inputs down to 3.5V, and peaks before falling to 0 at low input voltages. Although the current peak is higher than with the connection in Figure 6, this may be more useful because the quiescent current peaks at an input voltage well below the useful range of most batteries (Figure 9). Also, as IN falls below 5V, OUT tracks IN minus the dropout voltage. This connection still allows separate use of the SHDN input. Power Dissipation The MAX667 can regulate currents as high as 250mA and withstand input-output differential voltages as high Figure 10. MAX667 Load Current vs. Input-Output Differential Voltage +10V INPUT +2V/div +6V +5V OUTPUT +0.2V/div 1ms/div Figure 11. Output Response to +4V/100µs Input Step as 15.2V, but not simultaneously. The maximum power dissipation is dependent on the package and the temperature (see Absolute Maximum Ratings). Figure 10 shows the maximum output current at various inputoutput differential voltages for the plastic DIP and SO packages. The MAX667 can withstand short-circuit loads up to 1 second. Operation from AC Sources The MAX667 is a micropower CMOS regulator intended principally for battery operation. When operating from AC sources, consider power-supply ripple rejection. The MAX667’s error amplifier produces very low gain bandwidth, and the input power-supply rejection _______________________________________________________________________________________ 7 MAX667 +5V/Programmable Low-Dropout Voltage Regulator ___________________Chip Topography DD +5V OUTPUT 0.1V/div IN OUT 100mA OUTPUT CURRENT 10mA 0.107" (2.71mm) LBI 200µs/div LBO Figure 12. Output Response to 10mA/100mA Load Step with 10µF Output Capacitor (1.5Ω ESR) ratio (PSRR) is therefore not specified. Since the output must be connected to a 10µF or larger filter capacitor, the capacitor characteristics dominate the PSRR. Large values of input and output capacitors reduce the ripple. In addition, both DD and LBI/LBO can trigger on the lowest DC component of the ripple, particularly at high load currents. In the case of the low-battery detector, the ripple can be effectively filtered out by placing a capacitor to ground in parallel with the LBI input pin. The high resistance values that can be used for the voltage divider allow relatively small capacitance values to form an effective lowpass filter at 120Hz. When power is first applied, however, this filter tends to hold LBO low longer than normal. SET SHDN GND 0.070" (1.78mm) TRANSISTOR COUNT: 65 SUBSTRATE MUST BE LEFT UNCONNECTED Transient Considerations The low operating current and gain-bandwidth product of the internal reference and amplifier result in limited rejection of fast-step input changes. Negative-going steps, which occur in under 100µs, may turn off the output for several milliseconds. An input filter (nominally 10µF) is recommended if input changes greater than 1V and faster than 100µs (other than turn-on or turn-off) are anticipated. Figure 12 shows the output response to a 10mA/100mA instantaneous load step. The relationship between output-capacitor ESR and load-transient response is explained in the Output Capacitor section. Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 8 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1994 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.