19-1699; Rev 0; 9/00 500mA Low-Dropout Linear Regulator in µMAX Features The MAX1792 low-dropout linear regulator operates from a +2.5V to +5.5V supply and delivers a guaranteed 500mA load current with low 130mV dropout. The high-accuracy (±1%) output voltage is preset at an internally trimmed voltage (see Selector Guide) or can be adjusted from 1.25V to 5.0V with an external resistive divider. An internal PMOS pass transistor allows the low 80µA supply current to remain independent of load, making this device ideal for portable battery-operated equipment such as personal digital assistants (PDAs), cellular phones, cordless phones, base stations, and notebook computers. Other features include an active-low open-drain reset output with a 4ms timeout period that indicates when the output is out of regulation, a 0.1µA shutdown mode, short-circuit protection, and thermal shutdown protection. The device is available in a miniature 1.3W, 8-pin power-µMAX package with a metal pad on the underside of the package. ♦ Guaranteed 500mA Output Current ________________________Applications *Insert the desired two-digit suffix (see Selector Guide) into the blanks to complete the part number. Notebook Computers ♦ Low 130mV Dropout at 500mA ♦ Up to ±1% Output Voltage Accuracy Preset at 1.5V, 1.8V, 2.5V, 3.3V, or 5.0V Adjustable from 1.25V to 5.0V ♦ Reset Output with 4ms Timeout Period ♦ Low 80µA Ground Current ♦ 0.1µA Shutdown Current ♦ Thermal Overload Protection ♦ Output Current Limit ♦ Tiny 1.3W Power-µMAX Package Ordering Information PART* MAX1792EUA_ _ TEMP RANGE PIN-PACKAGE -40°C to +85°C 8 Power-µMAX Contact factory for other preset output voltages. Cellular and Cordless Telephones Selector Guide Personal Digital Assistants (PDAs) µMAX TOP MARK PART AND SUFFIX VOUT Base Stations MAX1792EUA15 1.5V or Adj. AAAE USB Hubs MAX1792EUA18 1.8V or Adj. AAAA Docking Stations MAX1792EUA25 2.5V or Adj. AAAB MAX1792EUA33 3.3V or Adj. AAAC MAX1792EUA50 5.0V or Adj. AAAD Palmtop Computers Typical Operating Circuit Pin Configuration TOP VIEW VIN = +2.5V TO +5.5V CIN 1µF IN NC OUT IN OUT VOUT COUT 3.3µF IN 1 8 OUT 7 OUT 3 6 SET SHDN 4 5 GND IN 2 MAX1792 RRST 100k MAX1792 ON SHDN RST SET GND OFF RST TO µC POWER-µMAX ________________________________________________________________ Maxim Integrated Products 1 For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. MAX1792 General Description MAX1792 500mA Low-Dropout Linear Regulator in µMAX ABSOLUTE MAXIMUM RATINGS IN, SHDN, RST, SET to GND ....................................-0.3V to +6V OUT to GND ................................................-0.3V to (VIN + 0.3V) Output Short-Circuit Duration ........................................Indefinite Continuous Power Dissipation (TA = +70°C) 8-Pin Power-µMAX (derate 17mW/°C above +70°C) .......1.3W Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+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 (VIN = VOUT(NOM) + 500mV, or VIN = +2.5V (whichever is greater), SHDN = IN, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Input Voltage Input Undervoltage Lockout SYMBOL CONDITIONS VIN VUVLO VOUT 2.0 +1 +1.5 IOUT = 100mA, TA = 0°C to +85°C -2 +2 IOUT = 1mA to 500mA, VIN > VOUT + 0.5V, TA = 0°C to +85°C -3 +3 1.25 5 VIN = +2.7V, VOUT set to 2.0V, IOUT = 100mA TA = +85°C 1.229 TA = 0°C to +85°C 1.219 IOUT VIN ≥ 2.7V 500 Short-Circuit Current Limit ILIM VOUT = 0, VIN ≥ 2.7V 0.55 SET Dual Mode™ Threshold VSET = 1.25V % V 1.281 mARMS 0.8 100 -100 IOUT = 1mA 80 IOUT = 500mA 110 1.8 A A 150 mV +100 nA 250 µA VOUT = 5.0V 120 225 VOUT = 3.3V 130 250 VOUT = 2.5V 210 360 0 +0.15 %/V IOUT = 1mA to 500mA 0.4 1.0 % 10Hz to 1MHz, COUT = 3.3µF (ESR < 0.1Ω) 115 IOUT = 500mA Line Regulation ∆VLNR VIN from (VOUT + 100mV) to 5.5V, ILOAD = 5mA Load Regulation ∆VLDR Output Voltage Noise % 1.271 1.6 50 VIN VOUT Dropout Voltage (Note 1) 1.250 UNITS V VOUT > 96% of nominal value, VIN ≥ 2.7V IQ V -1 Maximum Output Current Ground-Pin Current V 2.3 -1.5 VSET ISET 5.5 2.15 Preset VOUT < 2.5V SET Voltage Threshold (Adjustable Mode) SET Input Bias Current MAX Preset VOUT ≥ 2.5V Adjustable Output Voltage Range In-Regulation Current Limit TYP 2.5 Rising, 75mV hysteresis IOUT = 100mA, TA = +85°C Output Voltage Accuracy (Preset Mode) MIN -0.15 mV µVRMS SHUTDOWN Shutdown Supply Current SHDN Input Threshold SHDN Input Bias Current IOFF VIH VIL SHDN = GND, VIN = 5.5V 2.5V < VIN < 5.5V 2.5V < VIN < 5.5V SHDN = IN or GND 0.1 15 1.6 0.6 10 Dual Mode is a trademark of Maxim Integrated Products. 2 _______________________________________________________________________________________ 100 µA V nA 500mA Low-Dropout Linear Regulator in µMAX (VIN = VOUT(NOM) + 500mV, or VIN = +2.5V (whichever is greater), SHDN = IN, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.01 0.1 V 5.5 V 100 nA RESET OUTPUT Reset Output Low Voltage VOL RST sinking 1mA Operating Voltage Range for Valid Reset RST sinking 100µA RST Output High Leakage Current V RST = +5.5V RST Threshold RST Release Delay tRP 1.0 Rising edge, referred to VOUT(NOMINAL) 90 93 96 % Rising edge of OUT to rising edge of RST 1.5 4.5 8 ms THERMAL PROTECTION Thermal Shutdown Temperature Thermal Shutdown Hysteresis TSHDN 170 °C ∆TSHDN 20 °C ELECTRICAL CHARACTERISTICS (VIN = VOUT(NOM) + 500mV, or VIN = +2.5V (whichever is greater), SHDN = IN, TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER Input Voltage SYMBOL CONDITIONS VIN Input Undervoltage Lockout VUVLO Output Voltage Accuracy (Preset Mode) VOUT VSET Maximum Output Current IOUT Short-Circuit Current Limit ILIM Ground-Pin Current 5.5 V 2.0 2.3 V IOUT = 100mA -2 +2 IOUT = 1mA to 500mA -3 +3 1.25 5 V 1.212 1.288 V IOUT = 100mA 500 VOUT = 0 ISET VSET = 1.25V IQ IOUT = 1mA 0.55 1.8 A 50 150 mV -100 +100 nA 250 µA 225 VOUT = 3.3V 250 VOUT = 2.5V 360 IOUT = 500mA Line Regulation ∆VLNR VIN from (VOUT + 100mV) to 5.5V, ILOAD = 5mA Load Regulation ∆VLDR IOUT = 1mA to 500mA % mARMS VOUT = 5.0V VIN VOUT Dropout Voltage (Note 1) UNITS 2.5 SET Dual Mode Threshold SET Input Bias Current MAX Rising or falling Adjustable Output Voltage Range SET Voltage Threshold (Adjustable Mode) MIN -0.15 mV +0.15 %/V 1.0 % 15 µA SHUTDOWN Shutdown Supply Current IOFF SHDN = GND, VIN = +5.5V SHDN Input Threshold VIH 2.5V < VIN < 5.5V VIL 2.5V < VIN < 5.5V 0.6 SHDN = IN or GND 100 SHDN Input Bias Current I SHDN 1.6 V nA _______________________________________________________________________________________ 3 MAX1792 ELECTRICAL CHARACTERISTICS (continued) ELECTRICAL CHARACTERISTICS (continued) (VIN = VOUT(NOM) + 500mV, or VIN = +2.5V (whichever is greater), SHDN = IN, TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN MAX UNITS 0.1 V 5.5 V 100 nA RESET OUTPUT Reset Output Low Voltage RST sinking 1mA VOL Operating Voltage Range for Valid Reset RST sinking 100µA RST Output High Leakage Current V RST = +5.5V RST Threshold RST Release Delay tRP 1.0 Rising edge, referred to VOUT(NOMINAL) 90 96 % Rising edge of OUT to rising edge of RST 1.5 8 ms Note 1: Dropout voltage is defined as VIN - VOUT, when VOUT is 100mV below the value of VOUT measured when VIN = VOUT(NOM) + 0.5V. Since the minimum input voltage is 2.5V, this specification is only meaningful when VOUT(NOM) ≥ 2.5V. For VOUT(NOM) between 2.5V and 3.5V, use the following equations: Typical Dropout = -93mV/V ✕ VOUT(NOM) + 445mV; Guaranteed Maximum Dropout = -137mV/V ✕ VOUT(NOM) + 704mV. For VOUT(NOM) ≥ 3.5V: Typical Dropout = 120mV; Guaranteed Maximum Dropout = 225mV. Note 2: Specifications to -40°C are guaranteed by design, not production tested. Typical Operating Characteristics (MAX1792EUA33, VIN = VOUT + 500mV, SHDN = IN, CIN = 1µF, COUT = 3.3µF, TA = +25°C, unless otherwise noted.) 1.5 1.0 MAX1792-02 3.31 3.30 3.29 0 3.0 3.5 4.0 4.5 5.0 5.5 10 35 60 TEMPERATURE (°C) DROPOUT VOLTAGE vs. LOAD CURRENT GROUND-PIN CURRENT vs. INPUT VOLTAGE GROUND-PIN CURRENT vs. LOAD CURRENT TA = +25°C 100 TA = -40°C 50 IOUT = 500mA 120 100 80 IOUT = 0 60 40 20 0 LOAD CURRENT (mA) 130 VIN = 5.5V 85 120 110 VIN = 3.8V 100 90 80 70 60 0 100 200 300 400 500 600 700 800 140 GROUND-PIN CURRENT (µA) 140 GROUND-PIN CURRENT (µA) TA = +85°C 4 -15 LOAD CURRENT (mA) 200 0 -40 100 200 300 400 500 600 700 800 INPUT VOLTAGE (V) 250 150 0 MAX1792-04 2.5 3.29 3.27 3.27 2.0 3.30 3.28 3.28 0.5 3.31 MAX1792-06 2.0 VIN = VOUT + 500mV IOUT = 0 3.32 OUTPUT VOLTAGE (V) IOUT = 500mA 3.33 MAX1792-05 OUTPUT VOLTAGE (V) 3.32 OUTPUT VOLTAGE (V) IOUT = 0 2.5 3.33 MAX1792-01 3.5 3.0 OUTPUT VOLTAGE vs. TEMPERATURE OUTPUT VOLTAGE vs. LOAD CURRENT MAX1792-03 OUTPUT VOLTAGE vs. INPUT VOLTAGE DROPOUT VOLTAGE (mV) MAX1792 500mA Low-Dropout Linear Regulator in µMAX 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V) 0 100 200 300 400 500 600 700 800 LOAD CURRENT (mA) _______________________________________________________________________________________ 500mA Low-Dropout Linear Regulator in µMAX GROUND-PIN CURRENT vs. TEMPERATURE PSRR (dB) 80 75 -50 -40 -30 70 -20 -10 60 0 -15 10 35 60 85 0.01 0.1 1 10 100 TEMPERATURE (°C) FREQUENCY (kHz) OUTPUT SPECTRAL NOISE DENSITY vs. FREQUENCY OUTPUT NOISE DC TO 1MHz 10 COUT = 3.3µF IOUT = 50mA 1000 MAX1792-09 -40 MAX1792-10 GROUND-PIN CURRENT (µA) -60 85 65 OUTPUT SPECTRAL NOISE DENSITY (µV/√Hz) COUT = 3.3µF IOUT = 50mA -70 MAX1792-08 VIN = VOUT + 500 mV IOUT = 0 90 -80 MAX1792-07 95 POWER-SUPPLY REJECTION RATIO vs. FREQUENCY 1 VOUT 200µV/div 0.1 0.01 VOUT = 3.3V ROUT = 66Ω (50mA) 0.001 0.1 1 10 100 1000 20ms/div FREQUENCY (kHz) REGION OF STABLE COUT ESR vs. LOAD CURRENT LOAD-TRANSIENT RESPONSE MAX1792-12 MAX1792-11 100 IOUT 500mA/div COUT ESR (Ω) 10 COUT = 3.3µF 1 VOUT 20mV/div COUT = 10µF STABLE REGION 0.1 VIN = VOUT + 500mV CIN = 10µF ROUT = 660Ω TO 6.6Ω (5mA TO 500mA) 0.01 0 100 200 300 400 500 600 700 800 10µs/div LOAD CURRENT (mA) _______________________________________________________________________________________ 5 MAX1792 Typical Operating Characteristics (continued) (MAX1792EUA33, VIN = VOUT + 500mV, SHDN = IN, CIN = 1µF, COUT = 3.3µF, TA = +25°C, unless otherwise noted.) MAX1792 500mA Low-Dropout Linear Regulator in µMAX Typical Operating Characteristics (continued) (MAX1792EUA33, VIN = VOUT + 500mV, SHDN = IN, CIN = 1µF, COUT = 3.3µF, TA = +25°C, unless otherwise noted.) LOAD-TRANSIENT RESPONSE NEAR DROPOUT LINE-TRANSIENT RESPONSE MAX1792-14 MAX1792-13 6V IOUT 500mA/div VIN 1V/div 3V VOUT 50mV/div VOUT 10mV/div VIN = VOUT + 100mV CIN = 10µF ROUT = 660Ω TO 6.6Ω (5mA TO 500mA) 100µs/div 20µs/div SHUTDOWN WAVEFORM RST WAVEFORM MAX1792-15 MAX1792-16 2V 5V VSHDN 1V/div 0 VIN 2.5V/div 0 VOUT 2V/div 3V VOUT 1V/div 0 VRST 2V/div 0 ROUT = 6.6Ω (500mA) 0 ROUT = 66Ω (50mA) 20µs/div 20ms/div Pin Description 6 PIN NAME FUNCTION 1, 2 IN Regulator Input. Supply voltage can range from +2.5V to +5.5V. Bypass with a 1µF capacitor to GND (see Capacitor Selection and Regulator Stability). Connect both input pins together externally. 3 RST Open-Drain Active-Low Reset Output. RST remains low while the output voltage (VOUT) is below the reset threshold and for at least 4ms after VOUT rises above the reset threshold. Connect a 100kΩ pullup resistor to OUT to obtain an output voltage. 4 SHDN Active-Low Shutdown Input. A logic low reduces supply current to 0.1µA. In shutdown, the RST output is low and OUT is pulled low through an internal 5kΩ resistor. Connect to IN for normal operation. 5 GND Ground. This pin and the exposed pad also function as a heatsink. Solder both to a large pad or to the circuit-board ground plane to maximize power dissipation. 6 SET Voltage-Setting Input. Connect to GND for preset output. Connect to a resistive divider between OUT and GND to set the output voltage between 1.25V and 5.0V. 7, 8 OUT Regulator Output. Sources up to 500mA. Bypass with a 3.3µF low-ESR capacitor to GND. Use a 4.7µF capacitor for output voltages below 2V. Connect both output pins together externally. _______________________________________________________________________________________ 500mA Low-Dropout Linear Regulator in µMAX MAX1792 VIN = +2.5V TO +5.5V IN CIN 1µF IN THERMAL SENSOR MOSFET DRIVER WITH I LIM OUT ON VOUT = 1.25V TO 5.0V SHDN COUT 3.3µF OUT OFF SHUTDOWN LOGIC 5k VREF 1.25V ERROR AMPLIFIER LOGIC SUPPLY VOLTAGE (VOUT) RRST 100k R1 MAX1792 RST TO µC SET DELAY TIMER R2 93% VREF 100mV GND Figure 1. Functional Diagram Detailed Description The MAX1792 is a low-dropout, low-quiescent-current linear regulator designed primarily for battery-powered applications. The device supplies loads up to 500mA and is available with preset output voltages. As illustrated in Figure 1, the MAX1792 consists of a 1.25V reference, error amplifier, P-channel pass transistor, and internal feedback voltage-divider. The 1.25V reference is connected to the error amplifier, which compares this reference with the feedback voltage and amplifies the difference. If the feedback voltage is lower than the reference voltage, the pass-transistor gate is pulled lower, which allows more current to pass to the output and increases the output voltage. If the feedback voltage is too high, the passtransistor gate is pulled up, allowing less current to pass to the output. The output voltage is fed back through either an internal resistive divider connected to OUT or an external resistor network connected to SET. The Dual Mode comparator examines VSET and selects the feedback path. If VSET is below 50mV, the internal feedback path is used and the output is regulated to the factory-preset voltage. Additional blocks include an output current limiter, thermal sensor, and shutdown logic. Internal P-Channel Pass Transistor The MAX1792 features a 0.25Ω P-channel MOSFET pass transistor. Unlike similar designs using PNP pass transistors, P-channel MOSFETs require no base drive, which reduces quiescent current. PNP-based regulators also waste considerable current in dropout when the pass transistor saturates, and use high base-drive currents under large loads. _______________________________________________________________________________________ 7 500mA Low-Dropout Linear Regulator in µMAX MAX1792 Reset Output R1 = R2 IN OUT IN OUT VOUT 1.25V V IN = +2.5V TO +5.5V -1 VOUT CIN 1µF COUT 3.3µF MAX1792 R1 ON SHDN The reset output (RST) pulls low when OUT is less than 93% of the nominal regulation voltage. Once OUT exceeds 93% of the nominal voltage, RST goes high impedance after 4ms. RST is an open-drain N-channel output. To obtain a voltage output, connect a pullup resistor from RST to OUT. A 100kΩ resistor works well for most applications. RST can be used as a power-on-reset (POR) signal to a microcontroller (µC), or drive an external LED to indicate power failure. When the MAX1792 is shut down, RST is held low independent of the output voltage. If unused, leave RST grounded or unconnected. SET Current Limit OFF R2 RST GND Figure 2. Adjustable Output Using External Feedback Resistors The MAX1792 does not suffer from these problems and consumes only 110µA of quiescent current under heavy loads as well as in dropout. Output Voltage Selection The MAX1792’s Dual Mode operation allows operation in either a preset voltage mode or an adjustable mode. Connect SET to GND to select the preset output voltage. The two-digit part number suffix identifies the output voltage (see Selector Guide). For example, the MAX1792EUA33 has a preset 3.3V output voltage. The output voltage may also be adjusted by connecting a voltage-divider from OUT to SET to GND (Figure 2). Select R2 in the 25kΩ to 100kΩ range. Calculate R1 with the following equation: R1 = R2 [(VOUT / VSET) - 1] where VSET = 1.25V and VOUT may range from 1.25V to 5.0V. Shutdown Pull SHDN low to enter shutdown. During shutdown, the output is disconnected from the input and supply current drops to 0.1µA. When in shutdown, RST pulls low and OUT is discharged through an internal 5kΩ resistor. The capacitance and load at OUT determine the rate at which VOUT decays. SHDN can be pulled as high as +6V, regardless of the input and output voltage. 8 The MAX1792 monitors and controls the pass transistor’s gate voltage, limiting the output current to 0.8A (typ). This current limit doubles when the output voltage is within 4% of the nominal value to improve performance with large load transients. The output can be shorted to ground for an indefinite period of time without damaging the part. Thermal Overload Protection Thermal overload protection limits total power dissipation in the MAX1792. When the junction temperature exceeds TJ = +170°C, a thermal sensor turns off the pass transistor, allowing the device to cool. The thermal sensor turns the pass transistor on again after the junction temperature cools by 20°C, resulting in a pulsed output during continuous thermal overload conditions. Thermal overload protection protects the MAX1792 in the event of fault conditions. For continuous operation, do not exceed the absolute maximum junction-temperature rating of TJ = +150°C. Operating Region and Power Dissipation The MAX1792’s maximum power dissipation depends on the thermal resistance of the IC package and circuit board, the temperature difference between the die junction and ambient air, and the rate of air flow. The power dissipated in the device is P = IOUT x (VIN - VOUT). The maximum allowed power dissipation is 1.3W or: PMAX = (TJ(MAX) - TA) / ( θJC + θCA) where TJ - TA is the temperature difference between the MAX1792 die junction and the surrounding air, θJC is the thermal resistance from the junction to the case, and θ CA is the thermal resistance from the case through the PC board, copper traces, and other materials to the surrounding air. The MAX1792 package features an exposed thermal pad on its underside. This pad lowers the thermal resistance of the package by providing a direct heat con- _______________________________________________________________________________________ 500mA Low-Dropout Linear Regulator in µMAX POWER-µMAX PACKAGE OPERATING REGION AT TJ(MAX) = +150°C TA = +50°C CONTINUOUS CURRENT LIMIT 0.5 Noise, PSRR, and Transient Response TYPICAL VDROPOUT LIMIT MAXIMUM OUTPUT CURRENT (A) 0.6 0.4 0.3 0.2 The MAX1792 is designed to operate with low dropout voltages and low quiescent currents in battery-powered systems while still maintaining good noise, transient response, and AC rejection. See the Typical Operating Characteristics for a plot of Power-Supply Rejection Ratio (PSRR) vs. Frequency. When operating from noisy sources, improved supply-noise rejection and transient response can be achieved by increasing the values of the input and output bypass capacitors and through passive filtering techniques. TA = +85°C TA = +70°C MAXIMUM SUPPLY VOLTAGE LIMIT (VOUT = 1.25V) 0.1 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 INPUT-OUTPUT VOLTAGE DIFFERENTIAL (V) Figure 3. Power Operating Regions: Maximum Output Current vs. Supply Voltage duction path from the die to the PC board. Additionally, the MAX1792’s ground pin (GND) performs the dual function of providing an electrical connection to system ground and channeling heat away. Connect the exposed backside pad and GND to the system ground using a large pad or ground plane, or multiple vias to the ground plane layer. The MAX1792 delivers up to 0.5A(RMS) and operates with input voltages up to 5.5V, but not simultaneously. High output currents can only be sustained when inputoutput differential voltages are low, as shown in Figure 3. Applications Information Capacitor Selection and Regulator Stability Capacitors are required at the MAX1792’s input and output for stable operation over the full temperature range and with load currents up to 500mA. Connect a 1µF capacitor between IN and ground and a 3.3µF low equivalent series resistance (ESR) capacitor between OUT and ground. For output voltages less than 2V, use a 4.7µF low-ESR output capacitor. The input capacitor (CIN) lowers the source impedance of the input supply. Reduce noise and improve load-transient response, stability, and power-supply rejection by using larger output capacitors such as 10µF. The MAX1792 load-transient response graphs (see Typical Operating Characteristics) show two components of the output response: a DC shift from the output impedance due to the load current change, and the transient response. A typical transient response for a step change in the load current from 5mA to 500mA is 18mV. Increasing the output capacitor’s value and decreasing the ESR attenuates the overshoot. Input-Output (Dropout) Voltage A regulator’s minimum input-to-output voltage differential (dropout voltage) determines the lowest usable supply voltage. In battery-powered systems, this determines the useful end-of-life battery voltage. Because the MAX1792 uses a P-channel MOSFET pass transistor, its dropout voltage is a function of drain-tosource on-resistance (RDS(ON)) multiplied by the load current (see Typical Operating Characteristics): VDROPOUT = VIN - VOUT = RDS(ON) x IOUT The MAX1792 ground current remains below 150µA in dropout. Note: The MAX1792 has an exposed thermal pad on the bottom side of the package. Chip Information TRANSISTOR COUNT: 845 The output capacitor’s (COUT) ESR affects stability and output noise. Use output capacitors with an ESR of 0.1Ω or less to ensure stability and optimum transient _______________________________________________________________________________________ 9 MAX1792 response. Surface-mount ceramic capacitors have very low ESR and are commonly available in values up to 10µF. Connect CIN and COUT as close to the MAX1792 as possible to minimize the impact of PC board trace inductance. 0.7 MAX1792 500mA Low-Dropout Linear Regulator in µMAX 8LUMAXD.EPS Package Information Note: MAX1792 has an exposed thermal pad on the bottom side of the package 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. 10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.