MAX6480BL25BD3

19-2532; Rev 5; 12/07 KIT ATION EVALU E AILABL AV 300mA LDO Linear Regulators with Internal Microprocessor Reset Circuit General Description Features ♦ 3 ✕ 3 UCSP, 6-Pin SOT23, and 8-Pin TDFN Packages ♦ Preset +1.5V to +3.3V Output (100mV Increments) ♦ SET Pin for Adjustable Output Voltage ♦ 75μ VRMS LDO Output Voltage Noise (MAX6477–MAX6484) ♦ ±2.0% Accuracy Over Temperature ♦ Guaranteed 300mA Output Current ♦ Low Dropout Voltage 55mV at 150mA 114mV at 300mA ♦ 82μ A Supply Current, 0.1μ A Shutdown Current ♦ Input Reverse Current, Thermal and Short-Circuit Protection ♦ Microprocessor Reset with Four Timeout Options ♦ Push-Pull or Open-Drain RESET ♦ Manual Reset Input ♦ Remote Feedback Sense MAX6469–MAX6484 The MAX6469–MAX6484 are low-dropout linear regulators with a fully integrated microprocessor reset circuit. Each is available with preset output voltages from +1.5V to +3.3V in 100mV increments and delivers up to 300mA of load current. These devices consume only 82µA of supply current. The low supply current, low dropout voltage, and integrated reset functionality make these devices ideal for battery-powered portable equipment. The MAX6469–MAX6484 include a reset output that indicates when the regulator output drops below standard microprocessor supply tolerances (-7.5% or -12.5% of nominal output voltage). This eliminates the need for an external microprocessor supervisor, while ensuring that supply voltages and clock oscillators have stabilized before processor activity is enabled. Push-pull and opendrain active-low reset outputs are available, with reset timeout periods of 2.5ms, 20ms, 150ms, or 1200ms (min). The MAX6469/MAX6470/MAX6473–MAX6478/MAX6481– MAX6484 also have a shutdown feature that reduces the supply current to 0.1µA (typ). The MAX6471–MAX6474/ MAX6479–MAX6482 offer a manual reset input to assert a microprocessor reset while the regulator output is within specification. The MAX6475/MAX6476/MAX6483/ MAX6484 feature a remote feedback sense pin for use with an external NPN transistor for higher-current applications. The MAX6469–MAX6476 are available in 6-pin SOT23 and 8-pin TDFN packages. The MAX6477– MAX6484 are available in a 3 × 3 chip-scale package (UCSP™). All devices are specified for operation from -40°C to +85°C. Ordering Information PART MAX6469UT_ _ _D_-T MAX6469TA_ _ _D_-T* MAX6470UT_ _ _D_-T MAX6470TA_ _ _D_-T* TEMP RANGE -40°C to +85°C -40°C to +85°C -40°C to +85°C -40°C to +85°C PINPACKAGE 6 SOT23-6 8 TDFN-8 6 SOT23-6 8 TDFN-8 Applications Handheld Instruments (PDAs, Palmtops) PCMCIA Cards/USB Devices Cellular/Cordless Telephones CD/DVD Drives Notebook Computers Digital Cameras Bluetooth Modules/Wireless LAN *Future product—contact factory for availability. Note: The first “_ _”are placeholders for the output voltage levels of the devices. Desired output voltages are set by the suffix found in the Output Voltage Suffix Guide (Table 1). The third “_” is a placeholder for the reset threshold accuracy. Desired reset threshold accuracy is set by the suffix found in the Reset Threshold Accuracy Guide (Table 2). The “_” following the D is a placeholder for the reset timeout delay time. Desired reset timeout delay time is set by the suffix found in the Reset Timeout Delay Guide (Table 3). For example, the MAX6481BL30BD4-T has a 3.0V output voltage, 12.5% reset threshold tolerance, and a 1200ms (min) reset timeout delay. Sample stock is generally available on standard versions only (Table 4). Standard versions require a minimum order increment of 2.5k units. Nonstandard versions must be ordered in 10k-unit increments. Contact factory for availability. Ordering Information continued at end of data sheet. UCSP is a trademark of Maxim Integrated Products, Inc. Pin Configurations appear at end of data sheet. Typical Operating Circuits appear at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 300mA LDO Linear Regulators with Internal Microprocessor Reset Circuit MAX6469–MAX6484 ABSOLUTE MAXIMUM RATINGS (All voltages referenced to GND, unless otherwise noted.) IN, SHDN, OUT, FB ..................................................-0.3V to +7V MR, SET .......................................................-0.3V to (VIN + 0.3V) RESET (push-pull) ...................................-0.3V to (VOUT + 0.3V) RESET (open drain)..................................................-0.3V to +7V OUT Short Circuit .......................................................Continuous Input/Output Current (all pins except IN and OUT) ............20mA Continuous Power Dissipation (TA = +70°C) 3 x 3 UCSP (derate 10.5mW/°C above +70°C) ............840mW 6-Pin SOT23 (derate 9.1mW/°C above +70°C).............727mW 8-Pin TDFN (derate 24.4mW/°C above +70°C) ..........1951mW 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 Bump Reflow Temperature (Note 1) ................................+235°C Note 1: The MAX6477–MAX6484 are constructed using a unique set of packaging techniques that impose a limit on the thermal profile the devices can be exposed to during board-level solder attach and rework. This limit permits only the use of the solder profiles recommended in the industry-standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and Convection reflow. Pre-heating is required. Hand or wave soldering is not allowed. 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 + 0.5V) or +2.5V, whichever is greater, COUT = 3.3µF, TA = -40°C to +85°C. Typical specifications are at TA = +25°C, unless otherwise noted.) (Note 2) PARAMETER Input Voltage Range Input Undervoltage Lockout Supply Current (Ground Current) Shutdown Supply Current REGULATOR CIRCUIT Output Current Output Voltage Accuracy (Fixed Output Voltage Operation, Table 1) MAX6469–MAX6476 Output Voltage Accuracy (Fixed Output Voltage Operation, Table 1) MAX6477–MAX6484 Adjustable Output Voltage Range SET Reference Voltage SET Dual ModeTM Threshold SET Input Leakage Current 1mA ≤ IOUT ≤ 150mA, TA = +25°C 1mA ≤ IOUT ≤ 150mA, TA = -40°C to +85°C 1mA ≤ IOUT ≤ 300mA, TA = -40°C to +85°C 2mA ≤ IOUT ≤ 100mA, TA = +25°C 2mA ≤ IOUT ≤ 100mA, TA = -40°C to +85°C 2mA ≤ IOUT ≤ 300mA, TA = -40°C to +85°C (Note 3) VSET ISET VSET = 0, +1.2V (Note 3) SYMBOL VIN VUVLO IQ ISHDN VIN falling IOUT = 0 IOUT = 300mA TA = +25°C 300 -1.3 -2.3 -2.7 -1.1 -2.0 -2.5 VSET 1.200 CONDITIONS MIN 2.5 2.25 82 96 0.1 TYP MAX 5.5 2.47 136 1 UNITS V V µA µA mA +1.3 +2.3 +2.7 +1.1 +2.0 +2.5 5.0 1.258 ±100 V V mV nA % % 1.229 185 ±20 Dual Mode is a trademark of Maxim Integrated Products, Inc. 2 _______________________________________________________________________________________ 300mA LDO Linear Regulators with Internal Microprocessor Reset Circuit ELECTRICAL CHARACTERISTICS (continued) (VIN = (VOUT + 0.5V) or +2.5V, whichever is greater, COUT = 3.3µF, TA = -40°C to +85°C. Typical specifications are at TA = +25°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS VOUT = +3.3V (fixed output operation) VOUT = +3.0V (fixed output operation) ΔVDO VOUT = +2.8V (fixed output operation) VOUT = +2.5V (fixed output operation) Output Current Limit Input Reverse Leakage Current (OUT to IN Leakage Current) Startup Time Response SHDN Input Low Voltage SHDN Input High Voltage SHDN Input Current Thermal-Shutdown Temperature Thermal-Shutdown Hysteresis Line Regulation Load Regulation TSHDN ΔTSHDN VOUT = 1.5V, 2.5V ≤ VIN ≤ 5.5V, IOUT = 10mA VOUT = 1.5V, VIN = 2.5V, 1mA ≤ IOUT ≤ 150mA 10Hz to 100kHz, CIN = 0.1µF, IOUT = 100mA, VOUT = 1.5V MAX64_ _ _ _ _ _ A VTHOUT MAX64_ _ _ _ _ _ B MAX6469–MAX6476 MAX6477–MAX6484 VIL VIH SHDN = VIN or GND 0.7 × VIN -1 0.1 180 20 0.09 0.2 150 µVRMS 75 +1 VIN ≥ 2.5V (Note 3) VIN = 4V, VOUT = 5.5V, SHDN deasserted Rising edge of VIN or SHDN to VOUT within specification, RL = 68Ω, SET = GND, IOUT = 10mA IOUT = 50mA IOUT = 150mA IOUT = 300mA IOUT = 50mA IOUT = 150mA IOUT = 300mA IOUT = 50mA IOUT = 150mA IOUT = 300mA IOUT = 50mA IOUT = 150mA IOUT = 300mA 450 0.01 1.5 MIN TYP 23 55 114 25 61 114 26 65 137 30 75 158 MAX 32 90 180 40 100 190 50 110 210 60 150 250 UNITS MAX6469–MAX6484 Dropout Voltage (Notes 3, 4) mV mA µA 20 0.3 × VIN µs V V µA °C °C %/V % Output Voltage Noise RESET CIRCUIT VOUT Reset Threshold (VFB for MAX6475/MAX6476/ MAX6483/MAX6484) (Note 5) VOUT to Reset Delay (VFB for MAX6475/MAX6476/ MAX6483/MAX6484) D1 Reset Timeout Period (Note 6) tRP D2 D3 D4 2.5 20 150 1200 90 85 92.5 87.5 35 3.75 30 225 1800 5.0 40 300 2400 ms 95 90 %VOUT µs _______________________________________________________________________________________ 3 300mA LDO Linear Regulators with Internal Microprocessor Reset Circuit MAX6469–MAX6484 ELECTRICAL CHARACTERISTICS (continued) (VIN = (VOUT + 0.5V) or +2.5V, whichever is greater, COUT = 3.3µF, TA = -40°C to +85°C. Typical specifications are at TA = +25°C, unless otherwise noted.) (Note 2) PARAMETER MR Input Low Voltage MR Input High Voltage MR Minimum Input Pulse MR Glitch Rejection MR to Reset Delay MR Pullup Resistance RESET Output Voltage (Open Drain) Open-Drain Reset Output Leakage Current VOL ILKG VOL RESET Output Voltage Push-Pull VOH MR to OUT VOUT ≥ 1.0V, ISINK = 50µA, RESET asserted VOUT ≥ 1.5V, ISINK = 3.2mA, RESET asserted (Note 3) VOUT ≥ 1.0V, ISINK = 50µA, RESET asserted VOUT ≥ 1.5V, ISINK = 3.2mA, RESET asserted VOUT ≥ 2.0V, ISOURCE = 500µA, RESET deasserted 0.8 × VOUT 25 SYMBOL VIL VIH (Note 3) 0.7 × VOUT 1 120 200 40 70 0.3 0.4 1 0.3 0.4 V CONDITIONS MIN TYP MAX 0.3 × VOUT UNITS V V µs ns ns kΩ V µA Note 2: Note 3: Note 4: Note 5: Note 6: All devices are 100% production tested at +25°C and are guaranteed by correlation for TA = TMIN to TMAX. Guaranteed by design. Dropout voltage is defined as (VIN - VOUT) when VOUT is 2% below the value of VOUT for VIN = VOUT(NOM) + 1V. MAX6473/MAX6474/MAX6481/MAX6482 are guaranteed by design for VOUT < 2.5V. Select the reset timeout period using the Reset Timeout Delay Guide (Table 3). Insert the appropriate suffix in the part number when ordering. Typical Operating Characteristics (VIN = 5V, VOUT = 3.3V, COUT = 3.3µF, TA = +25°C, unless otherwise noted.) GROUND CURRENT vs. INPUT VOLTAGE (NO LOAD) MAX6469 toc01 GROUND CURRENT vs. INPUT VOLTAGE (300mA LOAD) MAX6469 toc02 MAXIMUM TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE MAX6469 toc03 120 100 GROUND CURRENT (μA) 80 60 40 20 0 0 1 2 3 4 5 6 INPUT VOLTAGE (V) +85°C +25°C -40°C 120 100 GROUND CURRENT (μA) +85°C 80 60 40 20 0 0 1 2 3 4 5 6 INPUT VOLTAGE (V) +25°C -40°C 150 125 PULSE DURATION (μs) 100 75 50 25 0 1 10 RESET THRESHOLD OVERDRIVE (mV) RESET ASSERTS ABOVE THIS LINE 100 4 _______________________________________________________________________________________ 300mA LDO Linear Regulators with Internal Microprocessor Reset Circuit MAX6469–MAX6484 Typical Operating Characteristics (continued) (VIN = 5V, VOUT = 3.3V, COUT = 3.3µF, TA = +25°C, unless otherwise noted.) REGION OF STABLE COUT ESR vs. LOAD CURRENT MAX6469 toc05 MAX6469 toc06 DROPOUT VOLTAGE vs. LOAD CURRENT MAX6469 toc04 PSRR vs. FREQUENCY 0 -10 -20 PSRR (dB) VOUT = 3.3V COUT = 3.3μF ILOAD = 30mA 5 125 VOUT = 3.3V COUT = 3.3μF 100 DROPOUT VOLTAGE (mV) 4 COUT ESR (Ω) 75 3 -30 -40 COUT = 4.7μF COUT = 3.3μF 50 2 25 -50 -60 0 50 100 150 200 250 300 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA) FREQUENCY (kHz) 1 STABLE REGION 0 0 0 50 100 150 200 250 300 LOAD CURRENT (mA) OUTPUT NOISE MAX6469 toc07 OUTPUT NOISE vs. FREQUENCY VIN = 2.5V VOUT = 1.5V IOUT = 100mA MAX6469 toc08 SHUTDOWN RESPONSE MAX6469 toc09 VIN = 4.5V VOUT = 3.3V ILOAD = 100mA 100 80 100μV/div VRMS (μV) 60 VSHDN 5V/div 40 VOUT 2V/div ILOAD = 50mA 20 0 500μs/div 10 100 1k FREQUENCY (Hz) 10k 100k 20ms/div STARTUP RESPONSE MAX6469 toc10 LOAD-TRANSIENT RESPONSE MAX6469 toc11 LOAD-TRANSIENT RESPONSE NEAR DROPOUT MAX6469 toc12 VIN 2V/div VIN = 5V VOUT = 3.3V ILOAD = 10mA TO 300mA VIN = 5V VOUT = 3.3V ILOAD = 100mA VOUT 2V/div VOUT 20mV/div VOUT 5mV/div 10μs/div 100μs/div 10μs/div _______________________________________________________________________________________ 5 300mA LDO Linear Regulators with Internal Microprocessor Reset Circuit MAX6469–MAX6484 Typical Operating Characteristics (continued) (VIN = 5V, VOUT = 3.3V, COUT = 3.3µF, TA = +25°C, unless otherwise noted.) LINE-TRANSIENT RESPONSE MAX6469 toc13 RESET DELAY RESPONSE MAX6469 toc14 RESET RESPONSE TO MR MAX6469 toc15 5V 4.5V VIN 500mV/div VIN 1V TO 4V 2V/div MR 2V/div VOUT 20mV/div AC-COUPLED RESET 2V/div VOUT = 3.3V ILOAD = 10mA 100μs/div 200ms/div 200ns/div RESET 2V/div RESET RESPONSE TO VIN RISING MAX6469 toc16 NORMALIZED OUTPUT VOLTAGE vs. TEMPERATURE NORMALIZED TO +25°C MAX6469 toc17 1.012 RESET 2V/div NORMALIZED OUTPUT VOLTAGE 1.006 ILOAD = 10mA 1.000 ILOAD = 300mA VOUT 2V/div VIN 5V/div 200ms/div 0.994 ILOAD = 150mA 0.988 -40 -15 10 35 60 85 TEMPERATURE (°C) 6 _______________________________________________________________________________________ 300mA LDO Linear Regulators with Internal Microprocessor Reset Circuit MAX6469/MAX6470/MAX6477/MAX6478 Pin Description PIN MAX6469/MAX6470 SOT23 1 2 3 TDFN 1, 2 3 4 BUMP MAX6477/MAX6478 UCSP A1 A2 A3 IN GND SHDN Regulator Input. Bypass IN to GND with a 0.1µF capacitor. Ground. This pin also functions as a heatsink. Solder to large pads or the circuit-board ground plane to maximize thermal dissipation. Active-Low Shutdown Input. Connect SHDN to VIN for normal operation. Active-Low Reset Output. RESET remains low while VOUT is below the reset threshold. RESET remains low for the duration of the reset timeout period after the reset conditions are terminated. RESET is available in open-drain and push-pull configurations. Feedback Input for Externally Setting the Output Voltage. Connect SET to GND to select the preset output voltage. Connect SET to an external resistor-divider network for adjustable output operation. Regulator Output. Bypass OUT to GND with a minimum 3.3µF low-ESR capacitor. Exposed Paddle. EP is internally connected to GND. Connect EP to the ground plane to provide a low thermal-resistance path from the IC junction to the PCB. Do not use as the electrical connection to GND. NAME FUNCTION MAX6469–MAX6484 4 5 C3 RESET 5 6 C2 SET 6 7, 8 C1 OUT — EP — — MAX6471/MAX6472/MAX6479/MAX6480 Pin Description PIN MAX6475/MAX6476 SOT23 1 2 3 TDFN 1, 2 3 4 BUMP MAX6483/MAX6484 UCSP A1 A2 A3 IN GND SHDN Regulator Input. Bypass IN to GND with a 0.1µF capacitor. Ground. This pin also functions as a heatsink. Solder to large pads or the circuit-board ground plane to maximize thermal dissipation. Active-Low Shutdown Input. Connect SHDN to VIN for normal operation. Active-Low Reset Output. RESET remains low while FB is below the reset threshold. RESET remains low for the duration of the reset timeout period after the reset conditions are terminated. RESET is available in open-drain and push-pull configurations. Feedback Input for Linear Regulator Controller or Remote Sense Applications. Connect FB to the external load (VCC) to obtain the fixed output voltage. Regulator Output. Bypass OUT to GND with a minimum 3.3µF low-ESR capacitor. Exposed Paddle. EP is internally connected to GND. Connect EP to the ground plane to provide a low thermal-resistance path from the IC junction to the PCB. Do not use as the electrical connection to GND. NAME FUNCTION 4 5 C3 RESET 5 6 C2 FB 6 7, 8 C1 OUT — EP — — _______________________________________________________________________________________ 7 300mA LDO Linear Regulators with Internal Microprocessor Reset Circuit MAX6469–MAX6484 MAX6473/MAX6474/MAX6481/MAX6482 Pin Description PIN MAX6473/MAX6474 SOT23 1 2 3 TDFN 1, 2 3 4 BUMP MAX6481/MAX6482 UCSP A1 A2 A3 IN GND SHDN Regulator Input. Bypass IN to GND with a 0.1µF capacitor. Ground. This pin also functions as a heatsink. Solder to large pads or the circuit-board ground plane to maximize thermal dissipation. Active-Low Shutdown Input. Connect SHDN to VIN for normal operation. Active-Low Reset Output. RESET remains low while VOUT is below the reset threshold or while MR is held low. RESET remains low for the duration of the reset timeout period after the reset conditions are terminated. RESET is available in open-drain and push-pull configurations. Active-Low Manual Reset Input. The reset output is asserted while MR is pulled low and remains asserted for the duration of the reset timeout period after MR transitions from low to high. Leave MR unconnected or connect to VOUT if not used. MR has an internal pullup resistor of 40kΩ (typ) to VOUT. Regulator Output. Bypass OUT to GND with a minimum 3.3µF (min) low-ESR capacitor. Exposed Paddle. EP is internally connected to GND. Connect EP to the ground plane to provide a low thermal-resistance path from the IC junction to the PCB. Do not use as the electrical connection to GND. NAME FUNCTION 4 5 C3 RESET 5 6 C2 MR 6 7, 8 C1 OUT — EP — — MAX6475/MAX6476/MAX6483/MAX6484 Pin Description PIN MAX6475/MAX6476 SOT23 1 2 3 TDFN 1, 2 3 4 BUMP MAX6483/MAX6484 UCSP A1 A2 A3 IN GND SHDN Regulator Input. Bypass IN to GND with a 0.1µF capacitor. Ground. This pin also functions as a heatsink. Solder to large pads or the circuit-board ground plane to maximize thermal dissipation. Active-Low Shutdown Input. Connect SHDN to VIN for normal operation. Active-Low Reset Output. RESET remains low while FB is below the reset threshold. RESET remains low for the duration of the reset timeout period after the reset conditions are terminated. RESET is available in open-drain and push-pull configurations. Feedback Input for Linear Regulator Controller or Remote Sense Applications. Connect FB to the external load (VCC) to obtain the fixed output voltage. Regulator Output. Bypass OUT to GND with a minimum 3.3µF low-ESR capacitor. Exposed Paddle. EP is internally connected to GND. Connect EP to the ground plane to provide a low thermal-resistance path from the IC junction to the PCB. Do not use as the electrical connection to GND. NAME FUNCTION 4 5 C3 RESET 5 6 C2 FB 6 7, 8 C1 OUT — EP — — 8 _______________________________________________________________________________________ 300mA LDO Linear Regulators with Internal Microprocessor Reset Circuit Detailed Description The MAX6469–MAX6484 are ultra-low, quiescent current, low-dropout linear regulators with an integrated microprocessor reset circuit. These devices guarantee 300mA (min) drive capabilities and are available with preset output voltages in 100mV increments between +1.5V and +3.3V. The internal reset circuit monitors the regulator output voltage and asserts the reset output when the regulator output is below the microprocessor supply tolerance. MAX6469–MAX6484 2.5V TO 5.5V IN OUT MAX6469–MAX6472 MAX6477–MAX6480 (MR) MANUAL RESET GND SET R1 COUT R2 Regulator The regulator core operates with +2.5V to +5.5V input voltage range. The output voltage is offered in 100mV increments between +1.5V and +3.3V (contact factory for other output voltage options). The MAX6469– MAX6472/MAX6477–MAX6480 offer an adjustable output voltage implemented with an external resistordivider network between OUT, SET, and GND (Figure 1). SET must be connected to either GND for fixed VOUT or to an external divider for adjustable VOUT. The MAX6469–MAX6472/MAX6477–MAX6480 automatically determine the feedback path depending on the connection of SET. The Typical Operating Circuit shows a typical connection for the MAX6469. OUT is an internally regulated low-dropout (LDO) linear regulator that powers a microprocessor. ( ) ARE FOR MAX6471/MAX6472/MAX6479/MAX6480 ONLY Figure 1. Adjustable Output Voltage Configuration the reset threshold. RESET asserts when MR is pulled low (MAX6471–MAX6474/MAX6479–MAX6482). RESET asserts when S HDN is pulled low (MAX6469/ MAX6470/MAX6473–MAX6478/MAX6481–MAX6484). Shutdown (MAX6469/MAX6470/MAX6473–MAX6478/MAX6481– MAX6484 only) SHDN allows the regulator to shut down, thereby reducing the total IIN consumption of the device. SHDN provides a digitally controlled active-low shutdown. In shutdown mode, the pass transistor, control circuit, and reference turn off to reduce the supply current to below 0.1µA. Connect SHDN to IN for normal operation. Manual Reset Input (MAX6471–MAX6474/MAX6479–MAX6482 only) Many µP-based products require manual reset capability, allowing the operator, a test technician, or external logic circuitry to initiate a reset. A logic low on M R asserts reset while the regulator output voltage is still within tolerance. Reset remains asserted while MR is low and for the reset timeout period (tRP) after MR returns high. The MR input has an internal pullup of 40kΩ (typ) to OUT. MR can be driven with TTL/CMOS logic levels or with open-drain/collector outputs. Connect a normally open switch from MR to GND to create a manual reset function; external debounce circuitry is not required. If MR is driven from long cables or the device is used in a noisy environment, connect a 0.1µF capacitor from MR to GND to provide additional noise immunity. Feedback Input (MAX6475/MAX6476/MAX6483/MAX6484 only) The feedback input (FB) connects to an internal resistordivider network (Functional Diagram). FB is not internally connected to VOUT, and as a result can be used to 9 Reset Circuit The reset supervisor circuit is fully integrated in the MAX6469–MAX6484 and uses the same reference voltage as the regulator. Two supply tolerance reset thresholds, -7.5% and -12.5%, are provided for each type of device. -7.5% Reset: Reset does not assert until the regulator output voltage is at least -5% out of tolerance and always asserts before the regulator output voltage is -10% out of tolerance. -12.5% Reset: Reset does not assert until the regulator output voltage is at least -10% out of tolerance and always asserts before the regulator output voltage is -15% out of tolerance. RESET Output A µP’s reset input starts the µP in a known state. The MAX6469–MAX6484 µP supervisory circuits assert RESET during power-up, power-down, and brownout conditions. RESET asserts when the input voltage is below the undervoltage lockout threshold. R ESET asserts when VOUT is below the reset threshold and remains asserted for at least the minimum selected reset timeout period (tRP, Table 3) after VIN rises above the undervoltage lockout threshold and VOUT rises above _______________________________________________________________________________________ 300mA LDO Linear Regulators with Internal Microprocessor Reset Circuit MAX6469–MAX6484 remotely sense the output voltage of the device. Using FB with an external npn transistor, the current drive capability can be increased according to the following equation (Figure 2): IOUT(TOTAL) = IOUT ✕ (β+1) The external npn pass transistor must meet specifications for current gain, power dissipation, and collector current. The beta influences the maximum output current the circuit can deliver. The largest guaranteed output current is given by ILOAD (max) = 300mA × beta (min). The transistor’s rated power dissipation must exceed the actual power dissipated in the transistor. The power dissipated (PD) equals the maximum load current (ILOAD (max)) times the maximum input-to-output voltage differential: PD = ILOAD (max) × (VIN (max) V OUT ). The rated transistor collector current must exceed the maximum load current. OUT-to-GND current through the LDO is 40µA (typ). The regulator output can be held up with an external super capacitor or backup battery at OUT until the IN battery is replaced. The RESET output is asserted while the IN battery is removed to place the system in a low-power mode. Volatile memory content is maintained until the super capacitor or battery voltage drops below RAM standby specifications. RESET deasserts when the IN battery has been replaced and OUT exceeds the desired reset threshold. For nonrechargeable backup battery applications, place a reverse diode between OUT and the backup battery (to prevent battery charging). The external diode does not affect the regulator’s dropout voltage because it is not between the LDO output and the processor/memory VCC supply. The diode can be replaced with a current-limiting resistor for rechargeable backup battery applications. Current Limit The MAX6469–MAX6484 include an internal currentlimit circuit that monitors and controls the pass transistor’s gate voltage, limiting the output current to 450mA (min). The output can be shorted to ground indefinitely without damaging the part. Reverse Leakage Protection Reverse OUT to IN Current An internal circuit monitors the MAX6469–MAX6484 input and output voltages. When the output voltage is greater than the input voltage, the internal IN-to-OUT pass transistor and parasitic diode turn off. An external voltage applied to OUT does not reverse charge a battery or power source applied to IN (the leakage path from OUT to IN is 0.01µA typ). When the output voltage exceeds the input voltage, OUT powers the device and shutdown must be logic high (greater than 0.7 ✕ VOUT). RESET asserts until IN exceeds OUT and OUT is above the specified VTHOUT threshold (based on the selected or adjusted regulator OUT nominal voltage). Thermal Shutdown When the junction temperature (TJ) exceeds +180°C (typ), the thermal sensor signals the shutdown logic, turning off the pass transistor and allowing the IC to REMOVABLE LITHIUM ION OR 3-CELL ALKALINE IN OUT Reverse OUT to Ground Current The MAX6469–MAX6484 maintain a low OUT-to-GND reverse-current flow when the IN power source is removed. When IN floats (input battery removed) and SHDN is pulled up to VOUT (by an external diode), the 5.0V MAX6469– MAX6484 SHDN 3.3μF 3.0V LITHIUM μP MEMORY IN OUT 1A TOTAL CURRENT VCC = 3.3V REMOVABLE LITHIUM ION OR 3-CELL ALKALINE IN OUT MAX6475/MAX6476 MAX6483/MAX6484 FB 330Ω 3.3μF 0.1μF RPULLUP μP MAX6469– MAX6484 SHDN 3.3μF μP SUPERCAP MEMORY GND RESET Figure 2. High-Current, External Transistor Application 10 Figure 3. Battery Backup ______________________________________________________________________________________ 300mA LDO Linear Regulators with Internal Microprocessor Reset Circuit cool. The thermal sensor turns the pass transistor on again after the IC’s junction temperature cools by 20°C, resulting in a pulsed output during continuous thermal overload conditions. Thermal overload protection is designed to protect the MAX6469–MAX6484 in the event of fault conditions. For continuous operation, do not exceed the absolute maximum junction temperature rating of TJMAX = +150°C. Operating Region and Power Dissipation The MAX6469–MAX6484’s maximum power dissipation depends on the thermal resistance of the case and circuit board, the temperature difference between the die junction and the ambient air, and the rate of airflow. The power dissipation across the device is: P = IOUT (VIN - VOUT) The maximum power dissipation is: PMAX = (TJ - TA) / (ØJB + ØBA) where TJ - TA is the temperature difference between the die junction and the surrounding air, ØJB (or ØJC) is the thermal resistance of the package, and ØBA is the thermal resistance through the PC board, copper traces, and other materials to the surrounding air. The MAX6469–MAX6476 TDFN package Ø JC = 41°C/W, and the MAX6469–MAX6476 SOT package Ø JC = 110°C/W. The MAX6469–MAX6484’s ground pin (GND) performs the dual function of providing an electrical connection to the system ground and channeling heat away. Connect GND to the system ground using a large pad or ground plane. For continuous operation, do not exceed the absolute maximum junction temperature rating of TJMAX = +150°C. Choose R2 = 50kΩ to maintain stability, accuracy and high-frequency power-supply rejection. Avoid selecting resistor values greater than 100kΩ. In preset voltage mode, the impedance between SET and ground should always be less than 50kΩ. In most applications, connect SET directly to ground. MAX6469–MAX6484 Low-Noise UCSP Output MAX6477–MAX6484 UCSP products include internal filtering to yield low output noise without an additional external bypass capacitor. The devices yield 75µVRMS (typ) output noise (for VOUT = 3.0V) and 150µVRMS (for V OUT = 3.3V). This low-noise feature makes the MAX6477–MAX6484 ideal for audio applications. Capacitor Selection and Regulator Stability For stable operation over the full temperature range and with load currents up to 300mA, use a 3.3µF (min) ceramic output capacitor with an ESR