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19-1422; Rev 1; 12/99
Low-Dropout, 300mA Linear Regulator in MAX
General Description
The MAX8860 low-noise, low-dropout linear regulator operates from a +2.5V to +6.5V input and is guaranteed to deliver 300mA. Typical output noise for this device is 60VRMS, and typical dropout is 105mV at 200mA. In addition to the six available preset output voltages (+1.8V, +2.5V, +2.77V, +2.82V, +3.0V, and +3.3V), the Dual ModeTM feature allows the device to be configured as an adjustable output regulator from +1.25V to +6.5V. Designed with an internal P-channel MOSFET pass transistor, the MAX8860 has a low 120A supply current. An output fault-detection circuit indicates loss of regulation. Other features include a 10nA, logic-controlled shutdown mode, short-circuit and thermal-shutdown protection, and reverse battery protection. The MAX8860 is available in a miniature 8-pin MAX package. o High Output Current (300mA) o Low Output Voltage Noise: 60VRMS o Low 105mV Dropout at 200mA Output o Low 120A No-Load Supply Current o Thermal-Overload and Short-Circuit Protection o Reverse Battery Protection o 10nA Logic-Controlled Shutdown o FAULT Indicator o Small, Space-Saving MAX Package (1.1mm max height) o Small 2.2F Output Capacitor Saves Space and Cost
Features
MAX8860
Applications
Wireless Handsets DSP Core Power PCMCIA Cards Hand-Held Instruments Palmtop Computers Electronic Planners
MAX8860EUA18 MAX8860EUA25 MAX8860EUA27 MAX8860EUA28 MAX8860EUA30 MAX8860EUA33 -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C PART
Ordering Information
TEMP. RANGE PINPACKAGE 8 MAX 8 MAX 8 MAX 8 MAX 8 MAX 8 MAX VOUT (V) +1.80 +2.50 +2.77 +2.82 +3.00 +3.30
Typical Operating Circuit
INPUT +2.5V TO +6.5V OUTPUT UP TO 300mA R1 100k C2 2.2F
IN
OUT
Pin Configuration
TOP VIEW
OUT IN GND OUT 1 2 3 4 8 FAULT SHDN CC SET
MAX8860
C1 2.2F SHDN SET GND OUT FAULT CC
FAULTDETECT OUTPUT
C3 33nF
MAX8860
7 6 5
MAX Dual Mode is a trademark of Maxim Integrated Products. ________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769.
Low-Dropout, 300mA Linear Regulator in MAX MAX8860
ABSOLUTE MAXIMUM RATINGS
IN, SHDN to GND .......................................................-7V to +7V SHDN to IN ...............................................................-7V to +0.3V SET, CC, FAULT to GND ..........................................-0.3V to +7V OUT to GND .............................................. -0.3V to (VIN + 0.3V) FAULT Sink Current ...........................................................20mA Continuous Output Current ..............................................330mA Output Short-Circuit Duration ....................................Continuous Continuous Power Dissipation (TA = +70C) 8-Pin MAX (derate 4.1mW/C above +70C) ............330mW Thermal Resistance (JA) 8-Pin MAX ............................................................+244C/W Operating Temperature Range MAX8860EUA_ _ ...........................................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range ............................-65C to +150C Lead Temperature (soldering, 10sec) ............................+300C
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 = +3.6V, CCC = 33nF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Input Voltage (Note 2) MAX8860EUA33 MAX8860EUA30 TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C CONDITIONS MIN 2.5 3.24 3.21 2.95 2.92 2.78 2.75 2.73 2.70 2.46 2.43 1.77 1.755 1.230 1.220 1.25 DC average current rating IOUT = 0 IOUT = 300mA TA = +25C TA = +85C 300 330 SET = GND VOUT = 0, SHDN = GND IOUT = 1mA Dropout Voltage (Note 4) Line Regulation Load Regulation IOUT = 200mA IOUT = 300mA VIN = +2.5V to +6.5V, SET = OUT, IOUT = 1mA IOUT = 100A to 300mA SET = OUT SET = GND -0.1 770 120 165 0.01 0.05 0.6 105 155 0.01 0.0001 0.0006 0.1 %/V %/mA 220 mV 1 270 1.248 1.80 2.50 2.77 2.82 3.00 3.3 TYP MAX 6.5 3.35 3.38 3.05 3.08 2.87 2.90 2.81 2.84 2.54 2.57 1.83 1.845 1.267 1.275 6.5 V V mA mA A A V UNITS V
Output Voltage
TA = +25C 100A < IOUT MAX8860EUA28 TA = -40C to +85C < 300mA, VIN = VOUT +1V, TA = +25C MAX8860EUA27 SET = GND TA = -40C to +85C MAX8860EUA25 MAX8860EUA18 TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C
SET Threshold Voltage Adjustable Output Voltage Range (Note 3) Maximum Output Current Output Current Limit Supply Current Shutdown Supply Current
SET = OUT, VIN = +2.5V to +6.5V, IOUT = 1mA
2
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Low-Dropout, 300mA Linear Regulator in MAX
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +3.6V, CCC = 33nF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Output Voltage Noise Output Voltage Noise Density SHDN Input Threshold SHDN Input Bias Current SET Input Leakage Current (Note 3) FAULT Detection Voltage (Note 5) FAULT Output Low Voltage FAULT Output Off-Leakage Current Thermal Shutdown Temperature Thermal Shutdown Hysteresis Start-Up Time Note 1: Note 2: Note 3: Note 4: COUT = 10F, VOUT to 90% of final value IOUT = 10mA, 10Hz < f < 100kHz CONDITIONS COUT = 2.2F COUT = 10F COUT = 100F 10Hz < f < 100kHz, COUT = 10F VIH, 2.5V VIN 5.5V VIL, 2.5V VIN 5.5V SHDN = GND or IN VSET = +1.3V SET = GND, IOUT = 200mA VIN = +2.5V, ISINK = 2mA V FAULT = +3.6V TA = +25C TA = +85C 0.01 0.5 170 20 120 TA = +25C TA = +85C TA = +25C TA = +85C 0.01 0.5 0.01 0.5 130 280 0.25 100 2.5 2.0 0.4 100 MIN TYP 65 60 55 190 nVHz V V nA nA mV V nA C C s VRMS MAX UNITS
MAX8860
Specifications to -40C are guaranteed by design and not production tested. Guaranteed by line-regulation test. Adjustable mode only. The dropout voltage is defined as VIN - VOUT when VOUT is 100mV below the value of VOUT for VIN = VOUT +2V. Since the minimum input voltage is 2.5V, this is applicable only for voltages of 2.5V or higher. Note 5: The FAULT detection voltage is the difference from input to output voltage. Maintain the input above this level to ensure good line and load regulation.
Typical Operating Characteristics
(VIN = VOUT + 0.5V, CIN = COUT = 2.2F, CCC = 33nF, TA = +25C, unless otherwise noted.)
NORMALIZED OUTPUT VOLTAGE vs. LOAD CURRENT
MAX8860 toc01
NORMALIZED OUTPUT VOLTAGE vs. TEMPERATURE
MAX8860 toc02
SUPPLY CURRENT vs. LOAD CURRENT
180 160 SUPPLY CURRENT (A) 140 120 100 80 60 40 20 TA = +85C TA = +25C TA = -40C
MAX8860 toc03
0.4 VOUT NORMALIZED AT IOUT = 0 OUTPUT VOLTAGE (%) 0.2
0.3 VOUT NORMALIZED AT +25C, IOUT = 0 0.2 OUTPUT VOLTAGE (%) 0.1 0 -0.1 -0.2 IOUT = 200mA
200
IOUT = 0 IOUT = 100mA
0
-0.2
-0.4 0 50 100 150 200 250 300 LOAD CURRENT (mA)
-0.3 -40 -20 0 20 40 60 80 TEMPERATURE (C)
0 0 50 100 150 200 250 300 LOAD CURRENT (mA)
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3
Low-Dropout, 300mA Linear Regulator in MAX MAX8860
Typical Operating Characteristics (continued)
(VIN = VOUT + 0.5V, CIN = COUT = 2.2F, CCC = 33nF, TA = +25C, unless otherwise noted.)
NO LOAD SUPPLY CURRENT vs. INPUT VOLTAGE
MAX8860 toc04
DROPOUT VOLTAGE vs. LOAD CURRENT
160 DROPOUT VOLTAGE (mV) 140 120 100 80 60 40 20 0 0 0 50 100 150 200 250 300 0 TA = +85C TA = -40C TA = +25C
MAX8860 toc05
FAULT DETECT THRESHOLD vs. LOAD CURRENT
MAX8860 toc06
200 180 160 SUPPLY CURRENT (A) 140 120 100 80 60 40 20 0 0 1 2 3 4 5 6 INPUT VOLTAGE (V) TA = -40C TA = +25C TA = +85C
180
250 FAULT DETECT THRESHOLD (mV)
200 FAULT = HIGH 150
100 FAULT = LOW
50
50
100
150
200
250
300
LOAD CURRENT (mA)
LOAD CURRENT (mA)
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
MAX8860 toc07
OUTPUT NOISE SPECTRAL DENSITY
MAX8860 toc08
OUTPUT NOISE (10Hz TO 1MHz)
MAX8860 toc09
0 -10 -20 -30 -40 -50 -60 -70 0.01 0.1 1 10 100
10 ILOAD = 10mA
NOISE (V/Hz)
1.0 COUT = 2.2F 0.1 COUT = 10F VOUT 500V/div ILOAD = 200mA
PSRR (dB)
0.01 1000 0.1 1 10 FREQUENCY (kHz) 100 1000 1ms/div FREQUENCY (kHz)
LOAD-TRANSIENT RESPONSE
MAX8860 toc10
LINE-TRANSIENT RESPONSE
+4.3V VIN +3.3V
MAX8860 toc12
200mA ILOAD 0
VOUT 20mV/div VIN = VOUT + 200mV VOUT 2mV/div
ILOAD = 200mA 400s/div 500s/div
4
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Low-Dropout, 300mA Linear Regulator in MAX MAX8860
Typical Operating Characteristics (continued)
(VIN = VOUT + 0.5V, CIN = COUT = 2.2F, CCC = 33nF, TA = +25C, unless otherwise noted.)
POWER-UP RESPONSE
MAX8860 toc13
POWER-DOWN RESPONSE
2V 0 FAULT
MAX8860 toc14
SHUTDOWN/POWER-UP
4V SHDN 2V 0 3V
MAX8860 toc15
4V 2V 0 4V 3V 2V 1V 0 5ms/div VOUT VIN FAULT
4V
4V 3V 2V 1V 0
VIN VOUT
2V VOUT 1V 0 2ms/div 400s/div
Pin Description
PIN 1, 4 2 3 5 6 7 8 NAME OUT IN GND SET CC SHDN FAULT FUNCTION Regulator Output. Bypass with 2.2F, low-ESR capacitor to GND for stable operation. Supply Input. Connect to power source (+2.5V to +6.5V). Bypass with 2.2F capacitor to GND. Ground Output Voltage Set. Connect to GND for internally set threshold. Connect to resistor-divider for adjustable output voltages. See Output Voltage Selection section for more information. Compensation Capacitor. Connect a 0.033F capacitor from CC to GND. Shutdown Input. Connect to IN for normal operation. Drive SHDN low to turn off the regulator. Fault Output. A high-impedance, open-drain output. When the MAX8860 is out of regulation, FAULT goes low. In shutdown, the FAULT pin is high impedance. Connect to GND if unused.
Detailed Description
The MAX8860 is a low-dropout, low-quiescent-current linear regulator designed primarily for battery-powered applications. It supplies an adjustable +1.25V to +6.5V output voltage or a fixed-voltage output of +1.8V (MAX8860EUA18), +2.5V (MAX8860EUA25), +2.77V (MAX8860EUA27), +2.82V (MAX8860EUA28), +3.0V (MAX8860EUA30), or +3.3V (MAX8860EUA33) for load currents up to 300mA. The devices with 2.77V and 2.82V nominal outputs are designed to guarantee minimum output voltages of 2.70V and 2.75V, respectively. The device consists of a +1.25V reference, error amplifier, MOSFET driver, P-channel pass transistor, Dual Mode comparator, fault detector, and internal-feedback voltage divider (Figure 1). The 1.25V bandgap reference is connected to the error amplifier's inverting input. The error amplifier compares
this reference to the selected feedback voltage and amplifies the difference. The MOSFET driver reads the error signal and applies the appropriate drive to the Pchannel pass transistor. If the feedback voltage is lower than the reference voltage, the pass-transistor gate is pulled lower, allowing more current to pass and increasing the output voltage. If the feedback voltage is higher than the reference voltage, the pass-transistor gate is driven higher, allowing less current to pass to the output. The output voltage is fed back through either an internal resistor voltage divider connected to OUT, or an external resistor network connected to SET. The Dual Mode comparator examines VSET and selects the feedback path. If V SET is below 60mV, internal feedback is used and the output voltage is regulated to the preset output voltage. Additional blocks include an output current limiter, reverse battery protection, a thermal sensor, a fault detector, and shutdown logic.
5
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Low-Dropout, 300mA Linear Regulator in MAX MAX8860
IN SHDN REVERSE BATTERY PROTECTION CC
ERROR AMP SHUTDOWN LOGIC
MOS DRIVER WITH ILIMIT
P
OUT SET FAULT DETECT
MAX8860
THERMAL SENSOR
1.25V REF DUAL-MODE COMPARATOR 60mV
FAULT
GND
Figure 1. Functional Diagram
Internal P-Channel Pass Transistor
The MAX8860 features a 0.5 typical P-channel MOSFET pass transistor. This provides several advantages over similar designs using PNP pass transistors, including longer battery life. PNP-based regulators waste considerable amounts of current in dropout when the pass transistor saturates. They also use high basedrive currents under large loads. The P-channel MOSFET requires no base-drive current, which reduces quiescent current considerably. The MAX8860 consumes less than 165A of quiescent current whether in dropout, light-load, or heavy-load applications (see Typical Operating Characteristics).
OUTPUT VOLTAGE IN OUT
CIN 2.2F BATTERY
MAX8860
SHDN SET
R1 COUT 2.2F R2 100k
CC 33nF
FAULT GND
Output Voltage Selection
The MAX8860 features Dual Mode operation: it operates in either a preset voltage mode or an adjustable mode. In preset voltage mode, internal, trimmed feedback resistors set the output voltage to an adjustable +1.25V to +6.5V output voltage or a fixed-voltage output of +1.8V (MAX8860EUA18), +2.5V (MAX8860EUA25), +2.77V (MAX8860EUA27), +2.82V (MAX8860EUA28), +3.V (MAX8860EUA30), or +3.3V (MAX8860EUA33). Select this mode by connecting SET to ground. In adjustable mode, select an output between 1.25V and 6.5V using two external resistors connected as a voltage divider to SET (Figure 2). Calculate the output voltage with the following equation:
Figure 2. Adjustable Output Using External Feedback Resistors
R1 VOUT = VSET 1 + R2 where VSET = 1.25V. To simplify resistor selection, use the following equation: V R1 = R2 OUT - 1 VSET
6
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Low-Dropout, 300mA Linear Regulator in MAX
Choose R2 = 100k to optimize power consumption, accuracy, and high-frequency power-supply rejection. Ensure that the total current through the external resistive feedback and load resistors is not less than 10A. Since the VSET tolerance is typically less than 20mV, set the output using fixed resistors instead of trim pots. In preset voltage mode, connect SET to GND. Keep impedances between SET and ground to less than 100k. Otherwise, spurious conditions can cause VSET to exceed the 60mV Dual Mode threshold. The maximum power dissipation is: PMAX = (TJMAX - TA) / JA where: TJMAX = +150C TA is the ambient temperature JA = 244C/W The MAX8860's pins perform the dual function of providing an electrical connection as well as channeling heat away from the die. Use wide circuit-board traces and large, solid copper polygons to improve power dissipation. Using multiple vias to buried ground planes further enhances thermal conductivity.
MAX8860
Shutdown
Drive SHDN low to place the MAX8860 in shutdown mode. In shutdown mode, the pass transistor, control circuit, reference, and all biases are turned off, reducing the supply current to typically 10nA. Connect SHDN to IN for normal operation.
Reverse Battery Protection
The MAX8860 has a unique protection scheme that limits the reverse supply current to less than 1mA when either V IN or V S HDN falls below GND. The circuitry monitors the polarity of these two pins, disconnecting the internal circuitry and parasitic diodes when the applied voltage is reversed. This feature prevents the device from overheating and damaging an improperly installed battery.
Current Limit
The MAX8860 includes short-circuit protection. It includes a current limiter that controls the pass transistor's gate voltage to limit the output current to about 770mA. For design purposes, the minimum current limit is 330mA.
Thermal-Overload Protection
Thermal-overload protection limits total power dissipation in the MAX8860. When the junction temperature (TJ) exceeds +170C, the thermal sensor sends a signal to the shutdown logic, turning off the pass transistor and allowing the IC to cool. The pass transistor turns on again after the IC's junction temperature typically cools by 20C, resulting in a pulsed output during continuous thermal-overload conditions. Thermal-overload protection is designed to protect the MAX8860 against fault conditions. Stressing the device with high-load currents and high input-output differential voltages (which result in die temperatures above +125C) may cause a momentary overshoot (2% to 8% for 200ms) when the load is completely removed. Remedy this by raising the minimum load current from 0 (+125C) to 100A (+150C). This is accomplished with an external load resistor. For continuous operation, do not exceed the absolute maximum junction temperature rating of +150C.
Integrator Circuitry
The MAX8860 uses an external 33nF compensation capacitor for minimizing load- and line-regulation errors and for lowering output noise. When the output voltage shifts due to varying load current or input voltage, the integrator capacitor voltage is raised or lowered to compensate for the systematic offset at the error amplifier. Compensation is limited to 5% to minimize transient overshoot when the device goes out of dropout, current limit, or thermal shutdown.
Fault-Detection Circuitry
When the output voltage goes out of regulation--such as during dropout, current limit, or thermal shutdown-- FAULT goes low. In addition, the fault-detection circuitry detects when the input-to-output voltage differential is insufficient to ensure good load and line regulation at the output. When the input-to-output voltage differential is less than 130mV for a load current of 200mA, FAULT also goes low. The differential threshold is designed to be always higher than and track with the dropout voltage, and to scale proportionally with load current (see Fault Detect Threshold vs. Load Current graph in the Typical Operating Characteristics). The FAULT pin is an open-drain N-channel MOSFET. To create a voltage level output, connect a pull-up resistor from FAULT to OUT. To minimize current consumption, make this resistor as large as practical. A 100k resistor works well for most applications.
Operating Region and Power Dissipation
Maximum power dissipation of the MAX8860 depends on the thermal resistance of the case and circuit board, the temperature difference between the die junction and ambient air, and the rate of air flow. The power dissipated by the device is: P = IOUT (VIN - VOUT)
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7
Low-Dropout, 300mA Linear Regulator in MAX MAX8860
VIN > +5.5V Minimum Load Current Requirements
When operating the MAX8860 with an input voltage above +5.5V, a minimum load current of 20A is required to maintain regulation in preset voltage mode. When setting the output with external resistors, ensure that the minimum current through the external feedback resistors and load is at least 30A. This applies only when the input voltage exceeds +5.5V. For input voltages less than +5.5V, the MAX8860 maintains regulation and stability without external loading.
Power-Supply Rejection and Operation from Sources Other than Batteries
The MAX8860 is designed to deliver low dropout voltage and low quiescent current in battery-powered systems. Power-supply rejection is 67dB at low frequencies and rolls off above 100kHz. At high frequencies, the output capacitor is the major contributor to the rejection of power-supply noise (see the Power-Supply Rejection Ratio vs. Frequency graph in the Typical Operating Characteristics). When operating from sources other than batteries, improve supply-noise rejection and transient response by increasing the values of the input and output capacitors, and by using passive filtering techniques (see the supply and load-transient responses in the Typical Operating Characteristics).
Applications Information
Capacitor Selection and Regulator Stability
Typically, use a 2.2F capacitor on the input and a 2.2F capacitor on the output of the MAX8860. Capacitor type is not critical, as long as it has an ESR less than 0.5. Larger capacitor values and lower ESR provide better supply-noise rejection and transient response. Use higher-value capacitors (10F) if large, fast input or load transients are anticipated or if the device is located several inches from the power source. For stable operation over the full temperature range, with load currents up to 300mA, a minimum outputcapacitor value of 2.2F is recommended. There is no upper limit to capacitor size. The circuit used to generate the typical operating characteristics data used 2.2F, X7R, 16V (1206) ceramic capacitors. These capacitors typically have an ESR of 50m.
Load-Transient Considerations
The MAX8860 load-transient response graph (see Typical Operating Characteristics) shows the output response due to changing load current. Reduce overshoot by increasing the output capacitor's value and decreasing its ESR.
Input-Output (Dropout) Voltage
A regulator's minimum input-output voltage differential (or dropout voltage) determines the lowest usable supply voltage. In battery-powered systems, this determines the useful end-of-life battery voltage. Because the MAX8860 uses a P-channel MOSFET pass transistor, its dropout voltage is a function of RDS(ON) (typically 0.5) multiplied by the load current (see Electrical Characteristics).
Chip Information
TRANSISTOR COUNT: 148
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 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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