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19-2560; Rev 0; 7/02
KIT ATION EVALU LE B AVAILA
Low-Voltage, Low-Dropout Linear Regulators with External Bias Supply
General Description
The MAX1982/MAX1983 are low-voltage, low-dropout linear regulators with an external bias supply input. The 5V bias supply drives the gate of the internal N-channel pass transistor, making these devices ideal for applications that require low-voltage outputs from low-voltage inputs. The MAX1982 delivers 1.2V (3%) at 300mA from an input voltage of 1.25V to 5.5V. The MAX1983 delivers an adjustable output voltage from 0.8V to 2V. The MAX1982/MAX1983 include a current-limit and thermal shutdown that protects the regulator in the event of a fault condition. Both devices are offered in a 6-pin SOT23 package and are specified over the extended (-40C to +85C) temperature range. o Low-Cost 1.2V, 300mA VID Supply o 3% Output Voltage Accuracy o No Minimum Load Current Required o 1.25V to 5.5V Input Supply Voltage o 5V Input Bias Supply Voltage o Power-Good (PGOOD) Open-Drain Output with 1ms Rising Edge Propagation Delay (MAX1982) o Adjustable Output Voltage (MAX1983) o Low Supply Current (IBIAS + IIN = 165A typ) o 5A (max) Shutdown Supply Current o Tiny 6-Pin SOT23 Package
Features
MAX1982/MAX1983
Applications
Notebook Computers VID Power Supplies PDAs Cell Phones Low-Dropout Regulators with External Bias Supply
Ordering Information
PART MAX1982EUT-T MAX1983EUT-T TEMP RANGE -40C to +85C -40C to +85C PINPACKAGE 6 SOT23-6 6 SOT23-6 TOP MARK ABEA ABEB
Typical Operating Circuit
TOP VIEW
4.5V TO 5.5V BIAS IN 1.25V TO 5.5V 10F
Pin Configurations
BIAS 1 GND 2
6
IN OUT PGOOD
MAX1982
0.1F GND OUT
MAX1982
5 4
1.2V 10F
SHDN 3
ON SHDN OFF PGOOD
PGOOD
SOT23-6 Fixed Output Voltage
100k
BIAS 1 GND 2 SHDN 3
6
IN OUT ADJ
MAX1983
5 4
SOT23-6 Adjustable Output
________________________________________________________________ Maxim Integrated Products
1
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Low-Voltage, Low-Dropout Linear Regulators with External Bias Supply MAX1982/MAX1983
ABSOLUTE MAXIMUM RATINGS
ADJ, IN, BIAS, PGOOD, SHDN, OUT to GND..........-0.3V to +6V Output Short-Circuit Duration ............................................Infinite Continuous Power Dissipation (TA = +70C) 6-Pin SOT23 (derate 8.7mW/oC above +70C)............696mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65oC to +150C Lead Temperature (soldering, 10s) .................................+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
(Circuit of Figure 3, VIN = 1.8V, ILOAD = 1mA, CLOAD = 10F, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Input Voltage BIAS Voltage VOUT Voltage Range BIAS Input Undervoltage Lockout Shutdown Supply Current Quiescent BIAS Current Shutdown BIAS Current VOUT Input Bias Current MAX1983 ADJ Input Current REGULATOR CHARACTERISTICS Line Regulation MAX1982 1.20V Output Voltage Accuracy VOUT/ VIN VOUT ILOAD = 10mA, 1.5V < VIN < 5.5V TA = +25C, IOUT = 100mA TA = 0C to +85C, IOUT = 1mA to 300mA, VOUT + 0.5V < VIN < 5.5V TA = +25C, IOUT = 100mA VOUT TA = 0C to +85C, IOUT = 1mA to 300mA, VOUT + 0.5V < VIN < 5.5V ILOAD = 300mA ILOAD = 150mA VIN - VOUT = 1.3V 330 600 160 20 10Hz to 100kHz % of regulated output voltage VHYST -12.5 65 -9 10 -6 -0.15 -1 -3 -1 -3 +0.15 +1 +3 +1 +3 350 175 1400 % % %/V IIN IQ I SHDN 1.25V < VIN < 5.5V 4.5V < VBIAS < 5.5V 4.5V < VBIAS < 5.5V MAX1982: VIN = open, VOUT = 1.20V MAX1983: VIN = open, 0.8V < VOUT < 2.0V 0V < VADJ < 2.0V SYMBOL VIN VBIAS VOUT MAX1983 CONDITIONS MIN 1.25 4.5 0.8 3.8 4.1 1 140 1 TYP MAX 5.5 5.5 2.0 4.35 5 250 5 30 2 1 UNITS V V V V A A A A A
MAX1983 0.80V Output Voltage Accuracy Dropout Voltage Current Limit Thermal-Shutdown Temperature Thermal-Shutdown Hysteresis RMS Output Noise PGOOD COMPARATOR Comparator Threshold Comparator Hysteresis
VDO ILIM T SHDN
mV mA C C VRMS % mV
2
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Low-Voltage, Low-Dropout Linear Regulators with External Bias Supply
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 3, VIN = 1.8V, ILOAD = 1mA, CLOAD = 10F, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER LOGIC AND I/O SHDN Input High Voltage SHDN Input Low Voltage SHDN Input Current PGOOD Output Low Voltage PGOOD Output High Leakage Current DYNAMICS Positive Load Step Negative Load Step Ripple Rejection at VIN Startup Response Time Startup Overshoot PGOOD Propagation Delay tPD tON tRISE tFALL ILOAD = 1mA to full load, CLOAD = 10F ILOAD = full load to 1mA, CLOAD = 10F 10Hz < f < 10kHz, ILOAD = 300mA, CLOAD = 10F ILOAD = 300mA, CLOAD = 10F, 0% to 90% of nominal output voltage ILOAD = 300mA, CLOAD = 10F Falling edge, 3mV under trip threshold Rising edge within 5% of regulation level 1 10 50 -60 100 0.5 10 4 s s dB s % s ms PGOOD sinking 1mA 0 < VPGOOD < VIN -1 VIH VIL -1 2.4 0.8 +1 0.1 +1 V V A V A SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX1982/MAX1983
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 3, VIN = 1.8V, ILOAD = 1mA, CLOAD = 10F, TA = -40C to +85C, unless otherwise noted.) (Note 1)
PARAMETER Input Voltage BIAS Voltage VOUT Voltage Range BIAS Input Undervoltage Lockout Shutdown Supply Current Quiescent BIAS Current Shutdown BIAS Current VOUT Input Bias Current REGULATOR CHARACTERISTICS Line Regulation MAX1982 1.20V Output Voltage Accuracy VOUT/ VIN VOUT ILOAD = 10mA, 1.5V < VIN < 5.5V IOUT = 1mA to 300mA, VOUT + 0.5V < VIN < 5.5V -0.15 -3 +0.15 +3 %/V % IIN IQ I SHDN 1.25V < VIN < 5.5V 4.5V < VBIAS < 5.5V 4.5V < VBIAS < 5.5V MAX1982: VIN = open, VOUT = 1.20V MAX1983: VIN = open, 0.8V < VOUT < 2.0V SYMBOL VIN VBIAS VOUT MAX1983 CONDITIONS MIN 1.25 4.5 0.8 3.8 MAX 5.5 5.5 2.0 4.2 5 250 5 30 2 UNITS V V V V A A A A
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Low-Voltage, Low-Dropout Linear Regulators with External Bias Supply MAX1982/MAX1983
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 3, VIN = 1.8V, VOUT = 1.2V, ILOAD = 1mA, CLOAD = 10F, TA = -40C to +85C, unless otherwise noted.) (Note 1)
PARAMETER MAX1983 0.80V Output Voltage Accuracy Dropout Voltage Current Limit PGOOD COMPARATOR Comparator Threshold LOGIC AND I/O SHDN Input High Voltage SHDN Input Low Voltage SHDN Input Current PGOOD Output Low Voltage PGOOD Output High Leakage Current DYNAMICS PGOOD Propagation Delay tPD Rising edge within 5% of regulation level 1 4 ms PGOOD sinking 1mA 0 < VPGOOD < VIN -1 VIH VIL -1 2.4 0.8 +1 0.1 +1 V V A V A % of regulated output voltage -12.5 -6 % SYMBOL VOUT VDO ILIM CONDITIONS IOUT = 1mA to 300mA, VOUT + 0.5V < VIN < 5.5V ILOAD = 300mA ILOAD = 150mA VIN - VOUT = 1.3V 330 MIN -3 MAX +3 350 175 1400 UNITS % mV mA
Note 1: Specifications over temperature are guaranteed by design, not production tested. Note 2: VOUT is 1.2V for MAX1982. For MAX1983 VOUT is set to 1.2V with circuit of Figure 4.
Typical Operating Characteristics
(Circuit of Figure 3, TA = +25C, unless otherwise noted.)
INPUT CURRENT vs. INPUT VOLTAGE
MAX1982/83 toc01
BIAS INPUT CURRENT vs. INPUT VOLTAGE
MAX1982/83 toc02
GROUND CURRENT vs. OUTPUT CURRENT
MAX1982/83 toc03
30
150
175
BIAS INPUT CURRENT (A)
29 INPUT CURRENT (A)
28
140
GROUND CURRENT (A)
145
170
165
27
26 VBIAS = 5V 1.5 2.5 3.5 INPUT VOLTAGE (V) 4.5 5.5
135 VBIAS = 5V 130 1.5 2.5 3.5 INPUT VOLTAGE (V) 4.5 5.5
160 VBIAS = 5V VIN = 1.8V 155 0 50 100 150 200 250 300 OUTPUT CURRENT (mA)
25
4
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Low-Voltage, Low-Dropout Linear Regulators with External Bias Supply
Typical Operating Characteristics (continued)
(Circuit of Figure 3, TA = +25C, unless otherwise noted.)
INPUT CURRENT vs. TEMPERATURE
MAX1982/83 toc04
MAX1982/MAX1983
BIAS SUPPLY CURRENT vs. TEMPERATURE
MAX1982/83 toc05
DROPOUT VOLTAGE vs. OUTPUT CURRENT
VBIAS = 5V DROPOUT VOLTAGE (mV) 150
MAX1982/83 toc06
28.0 VBIAS = 5V 27.5 27.0
150 VBIAS = 5V 145 140 IBIAS (A) 135 130 125 120 115
200
IIN (A)
26.5 26.0 25.5 25.0 -40 -15 10 35 60 85 TEMPERATURE (C)
100
50
0 -40 -15 10 35 60 85 0 50 100 150 200 250 300 TEMPERATURE (C) OUTPUT CURRENT (mA)
OUTPUT VOLTAGE ERROR vs. OUTPUT CURRENT
MAX1982/83 toc07
OUTPUT VOLTAGE ERROR vs. TEMPERATURE
VIN = 1.8V 0.75 RELATIVE VOUT ERROR (%) 0.50 0.25 0 -0.25 -0.50 ILOAD = 0mA -0.75 -1.00 ILOAD = 200mA ILOAD = 300mA
MAX1982/83 toc08
SHORT-CIRCUIT CURRENT LIMIT vs. INPUT VOLTAGE
SHORT-CIRCUIT CURRENT LIMIT (mA) 700 600 500 400 300 200 100 0 1.50 2.50 3.50 INPUT VOLTAGE (V) 4.50 5.50
MAX1982/83 toc09
1.00 0.75 0.50 VOUT ERROR (%) 0.25 0 VBIAS = 5V VIN = 1.8V
1.00
800
-0.25 -0.50 -0.75
-1.00 0 50 100 150 200 250 300 OUTPUT CURRENT (mA)
-40
-15
10
35
60
85
TEMPERATURE (C)
SHORT-CIRCUIT CURRENT LIMIT vs. TEMPERATURE
MAX1982/83 toc10
POWER-SUPPLY REJECTION RATIO (VIN) vs. FREQUENCY
-10 -20 -30 PSRR (dB) -40 -50 -60 -70 -80 -90 VIN = 2.1V VP-P = 0.6V ILOAD = 0
MAX1982/83 toc11
700 SHORT-CIRCUIT CURRENT LIMIT (mA)
0
650
600
550
500 -40 -15 10 35 60 85 TEMPERATURE (C)
-100 10 100 1k 10k 100k 1M FREQUENCY (Hz)
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Low-Voltage, Low-Dropout Linear Regulators with External Bias Supply MAX1982/MAX1983
Typical Operating Characteristics (continued)
(Circuit of Figure 3, TA = +25C, unless otherwise noted.)
POWER-SUPPLY REJECTION RATIO (VBIAS) vs. FREQUENCY
MAX1982/83 toc12
RIPPLE REJECTION RATIO (VIN) vs. FREQUENCY
-10 -20 -30 PSRR (dB) -40 -50 -60 -70 -80 -90 -100 IL = 100mA VIN = 3V VP-P = 0.4V IL = 300mA IL = 200mA
MAX1982/83 toc13
0 -10 -20 -30 PSRR (dB) -40 -50 -60 -70 -80 -90 -100 10 100 1k 10k 100k VBIAS = 5V VP-P = 0.6V ILOAD = 0
0
1M
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
FREQUENCY (Hz)
LINE TRANSIENT (NO LOAD)
MAX1982/83 toc14
LOAD TRANSIENT (1mA TO 300mA)
MAX1982/83 toc15
500mV/ div
2.4V VIN 1.8V
200mA/ div
300mA ILOAD
1mV/ div
VOUT 1mV/div 100s/div
10mV/ div
VOUT
10s/div
LOAD TRANSIENT (300mA TO 1mA)
MAX1982/83 toc16
LOAD TRANSIENT IN DROPOUT
MAX1982/83 toc17
200mA/ div
300mA ILOAD
200mA/ div
300mA ILOAD
10mV/ div
VOUT
50mV/ div
VOUT
10s/div
20s/div
6
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Low-Voltage, Low-Dropout Linear Regulators with External Bias Supply
Typical Operating Characteristics (continued)
(Circuit of Figure 3, TA = +25C, unless otherwise noted.)
UNDERVOLTAGE LOCKOUT
MAX1982/83 toc18
MAX1982/MAX1983
SHUTDOWN RESPONSE
MAX1982/83 toc19
5V 2V/ div VBIAS 2V/ div
5V VSHDN
1.2V 500mV/ div VOUT ILOAD = 300mA 100s/div 500mV/ div VOUT ILOAD = 300mA 100s/div
PGOOD RESPONSE
MAX1982/83 toc20
2V/ div
VOUT
500mV/ div
VPGOOD
1ms/div
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7
Low-Voltage, Low-Dropout Linear Regulators with External Bias Supply MAX1982/MAX1983
Pin Description
PIN NAME MAX1982 1 2 3 4 -- 5 6 MAX1983 1 2 3 -- 4 5 6 BIAS GND SHDN PGOOD ADJ OUT IN Bias Voltage. Input voltage to the control circuitry. BIAS powers all control blocks and the gate of the pass transistor. Bypass BIAS to GND with a 0.1F ceramic capacitor. Ground Shutdown Control Input. Drive SHDN low to enter the low-power shutdown state. Connect SHDN to BIAS for normal operation. Power-Good Output. The open-drain PGOOD output goes high at least 1ms after the output voltage has attained regulation. PGOOD asserts low 10s after the output falls by 10%. Feedback for Adjustable Output. Connect ADJ to the midpoint of a resistor-divider between OUT and GND for an adjustable output voltage between 0.8V and 2.0V. Regulator Output. Bypass OUT to GND with a 10F to 22F low-ESR ceramic capacitor. Internal Pass Transistor Input. IN connects to the drain of the internal power switch. Bypass IN to GND with a 10F ceramic capacitor. FUNCTION
Detailed Description
The MAX1982/MAX1983 are low-voltage, low-dropout linear regulators with an external bias supply input (see Figures 1 and 2). BIAS is powered by a 4.5V to 5.5V supply that is commonly available in laptop and desktop computers. The 5V bias supply drives the gate of the internal pass transistor, while a lower voltage input at the drain of the transistor (IN) is regulated to provide VOUT. Separating the bias input voltages yields higher efficiency. These devices are ideal for applications that require low-voltage outputs from low-voltage inputs. The MAX1982 delivers 1.2V (3%) at 300mA from an input voltage of 1.25V to 5.5V. The MAX1983 delivers an adjustable output voltage from 0.8V to 2V. The MAX1982 features an open-drain PGOOD output that transitions high 1ms after the output reaches regulation. PGOOD goes low within 10s of the output falling out of regulation by 120mV. Both devices feature current- and thermal-limiting circuitry that protect the MAX1982/MAX1983 from damage during fault conditions.
capacitor as close to the device as possible. The bias supply current remains low (250A) when the MAX1982/MAX1983 are in dropout.
Power-Supply Input
IN connects to the drain of the internal N-channel power transistor. IN may be as low as 1.25V, minimizing power dissipation. Bypass IN with a 10F or greater capacitor as close to the device as possible.
Shutdown
The MAX1982/MAX1983 feature a low-power shutdown mode that reduces quiescent current drawn to 1A (typ), and BIAS current consumption to less than 1A (typ). Driving SHDN low disables the voltage reference, error amplifier, gate-drive circuitry, and pass transistor (see Figure 2), and the device output enters a highimpedance state. Connect SHDN to BIAS for normal operation.
PGOOD Output
The MAX1982 provides an open-drain PGOOD output that goes high 1ms (min) after the output attains regulation (within 10% of the nominal output voltage). PGOOD transitions low 10s after the output falls out of regulation by 120mV, or when the device enters shutdown. Connect a pullup resistor from PGOOD to BIAS for a logic-level output. Use a 100k resistor to minimize current consumption.
Bias Supply Input
The BIAS input powers the control circuitry and provides the pass transistor gate drive. Power BIAS from a well-regulated 5V (10%) supply. Current drawn from the BIAS supply remains relatively constant with variations in VIN and load current (see the Typical Operating Characteristics). Bypass BIAS with a 0.1F or greater
8
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Low-Voltage, Low-Dropout Linear Regulators with External Bias Supply MAX1982/MAX1983
PGOOD
MAX1982
SHDN BIAS UVLO SHUTDOWN OVERTEMP 1ms DELAY
IN CURRENT SENSE
BIAS
0.8V REFERENCE
OUT
GND
Figure 1. MAX1982 Functional Diagram
MAX1983
SHDN BIAS UVLO SHUTDOWN OVERTEMP
IN CURRENT SENSE
BIAS
0.8V REFERENCE GM AV ADJ OUT
R1
R2 GND
Figure 2. MAX1983 Functional Diagram _______________________________________________________________________________________ 9
Low-Voltage, Low-Dropout Linear Regulators with External Bias Supply MAX1982/MAX1983
Current Limit
The MAX1982/MAX1983 limit the output current to 600mA (typ) in the event of an overload or output short circuit. The current limit prevents damage to the internal power transistor, but the device can enter thermal shutdown if the power dissipation is great enough to increase the die temperature above +160C (see the Thermal-Overload Protection section). GND as shown in Figure 4. Set the output voltage using the following equation: R1 VOUT = 0.8V 1+ R2 Set R2 at 40k and choose R1 to achieve the desired output voltage. Set VIN to higher than (VOUT + 400mV) to meet the dropout voltage requirement (see the Input/Output (Dropout) Voltage section). To ensure stability over the specified input voltage range, the minimum output capacitance must be 10F with a maximum ESR of 35m.
Thermal-Overload Protection
Thermal-overload protection limits the power dissipation in the MAX1982/MAX1983. When the die temperature exceeds +160C, the pass transistor turns off, allowing the device to cool. Normal operation resumes when the die temperature cools by 20C. A continuous thermal-overload condition results in a pulsed output. For continuous operation, do not exceed a junction temperature of +150C.
Operating Region and Power Dissipation
The maximum power dissipation of the MAX1982/ MAX1983 depends on the thermal resistance of the 6-pin SOT23 package and the circuit board, the temperature difference between the die and ambient air, and the rate of airflow. The power dissipated in the device is: PD = IOUT x ( VIN - VOUT ) The resulting maximum power dissipation is: PDISS(MAX) = TJ(MAX) - TA JC + CA
Applications Information
Output Voltage Selection
The MAX1982 output is fixed at 1.2V. The MAX1983 provides an adjustable output (0.8V to 2.0V). Connect ADJ to a resistive voltage-divider between OUT and
4.5V TO 5.5V BIAS 0.1F GND IN 10F 1.25V TO 5.5V
MAX1982
OUT 10F 1.2V
ON SHDN OFF 100k PGOOD
where TJ(MAX) is the maximum junction temperature (+150C) and TA is the ambient temperature, JC is the thermal resistance from the die junction to the package case, and CA is the thermal resistance from the case through the PC board, copper traces, and other materials to the surrounding air. For optimum power dissipation, use a large ground plane with good thermal contact to GND, and use wide input and output traces. When 1 square inch of copper is connected to the device, the maximum allowable power dissipation of a 6-pin SOT23 package is 696mW. The maximum power dissipation is derated by 8.7mW/C above TA = +70C. Extra copper on the PC board increases thermal mass, and reduces thermal resistance of the board. Refer to the MAX1982/MAX1983 EV kit for a layout example. The MAX1982/MAX1983 deliver up to 300mA and operate with input voltages up to 5.5V, but not simultaneously. High output currents can only be achieved when the input-output differential voltages are low (Figure 5).
Figure 3. MAX1982 Typical Application Circuit
4.5V TO 5.5V BIAS 0.1F GND IN
1.5V TO 5.5V 10F
MAX1983
OUT R1 20k 1.2V
ON SHDN OFF ADJ R2 40k 10F
Undervoltage Lockout (UVLO)
The undervoltage lockout (UVLO) circuit ensures that the regulator starts up with adequate voltage for the gate-drive circuitry to bias the internal pass transistor.
Figure 4. MAX1983 Typical Application Circuit 10
______________________________________________________________________________________
Low-Voltage, Low-Dropout Linear Regulators with External Bias Supply
350 MAXIMUM OUTPUT CURRENT (mA) 300 250 200 150 100 50 0 0 1 2 3 4 5 INPUT-OUTPUT DIFFERENTIAL VOLTAGE (V) TYPICAL DROPOUT VOLTAGE LIMIT MAXIMUM CONTINUOUS CURRENT
TA = +50C TA = +70C
TYPICAL SUPPLY VOLTAGE LIMIT
TA = +25C
The MAX1982/MAX1983 load-transient response graphs (see the 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 1mA to 300mA is 20mV. Increasing the output capacitor's value and decreasing the ESR attenuate the overshoot.
MAX1982/MAX1983
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, the dropout voltage determines the useful end-of-life battery voltage. Because the MAX1982/MAX1983 use an N-channel pass transistor, the dropout voltage is a function of the drain-to-source on-resistance (RDS(ON) = 1 max) multiplied by the load current (see the Typical Operating Characteristics): VDROPOUT = VIN - VOUT = RDS(ON) x IOUT
TJ = +150C
Figure 5. Power Operating Region--Maximum Output Current vs. Supply Voltage
The UVLO circuitry monitors V BIAS only. The UVLO threshold is 4.2V, and VBIAS must remain above this level for proper operation, regardless of the level of VIN.
Input Capacitor
Bypass IN to ground with a 10F or greater ceramic capacitor. Bypass BIAS to ground with a 0.1F ceramic capacitor for normal operation in most applications.
PC Board Layout Guidelines
The MAX1982/MAX1983 require proper layout to achieve the intended output power level, high efficiency, and low noise. Proper layout involves the use of a ground plane, appropriate component placement, and correct routing of traces using appropriate trace widths. 1) Minimize high-current ground loops. Connect the ground of the device, the input capacitor, and the output capacitor together at one point. 2) To optimize performance, a ground plane is essential. Use all available copper layers in applications where the device is located on a multilayer board. 3) Connect the input filter capacitor less than 10mm from IN. The connecting copper trace carries large currents and must be at least 2mm wide, preferably 5mm wide. 4) Use as much copper as necessary to increase the thermal resistance of the device. In general, more copper provides better heatsinking capabilities.
Output Capacitor
Bypass OUT to ground with a low-ESR ceramic capacitor greater than 10F. The ESR must be less than 35m. Choose an output capacitor to maintain the required output voltage tolerance during a load step. The change in output voltage is, t V = I ESR + COUT where I is the load current, COUT is the output capacitance, and t is the duration of the load step.
Noise, PSRR, and Transient Response
The MAX1982/MAX1983 operate with low-dropout voltage and low quiescent current in notebook computers while maintaining good noise, transient response, and AC rejection specifications. See the Typical Operating Characteristics for a graph of Power-Supply Rejection Ratio (PSRR) vs. Frequency. Improved supply-noise rejection and transient response can be achieved by increasing the values of the input and output capacitors and use passive filtering techniques when operating from noisy sources.
Chip Information
TRANSISTOR COUNT: 430 PROCESS: BiCMOS
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11
Low-Voltage, Low-Dropout Linear Regulators with External Bias Supply MAX1982/MAX1983
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
6LSOT.EPS
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.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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