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PDF MAX1982EUT-T Data sheet ( Hoja de datos )
| Número de pieza | MAX1982EUT-T | |
| Descripción | Low-Voltage / Low-Dropout Linear Regulators with External Bias Supply | |
| Fabricantes | Maxim Integrated | |
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19-2560; Rev 0; 7/02
EVAALVUAAILTAIOBNLEKIT
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 applica-
tions 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 (-40°C to +85°C) temperature range.
Applications
Notebook Computers
VID Power Supplies
PDAs
Cell Phones
Low-Dropout Regulators with External Bias
Supply
Features
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 = 165µA typ)
o 5µA (max) Shutdown Supply Current
o Tiny 6-Pin SOT23 Package
Ordering Information
PART
TEMP RANGE
MAX1982EUT-T -40°C to +85°C
MAX1983EUT-T -40°C to +85°C
PIN-
PACKAGE
6 SOT23-6
6 SOT23-6
TOP
MARK
ABEA
ABEB
Typical Operating Circuit
4.5V TO 5.5V
BIAS
0.1µF
MAX1982
GND
IN
OUT
ON
OFF
SHDN
PGOOD
1.25V TO 5.5V
10µF
1.2V
10µF
PGOOD
100kΩ
Pin Configurations
TOP VIEW
BIAS 1
6 IN
GND 2 MAX1982 5 OUT
SHDN 3
4 PGOOD
SOT23-6
Fixed Output Voltage
BIAS 1
6 IN
GND 2 MAX1983 5 OUT
SHDN 3
4 ADJ
SOT23-6
Adjustable Output
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
Low-Voltage, Low-Dropout Linear Regulators
with External Bias Supply
Typical Operating Characteristics (continued)
(Circuit of Figure 3, TA = +25°C, unless otherwise noted.)
INPUT CURRENT vs. TEMPERATURE
28.0
VBIAS = 5V
27.5
27.0
26.5
26.0
25.5
25.0
-40
1.00
0.75
0.50
0.25
0
-0.25
-0.50
-0.75
-1.00
0
-15 10 35 60
TEMPERATURE (°C)
OUTPUT VOLTAGE ERROR
vs. OUTPUT CURRENT
85
VBIAS = 5V
VIN = 1.8V
50 100 150 200 250 300
OUTPUT CURRENT (mA)
BIAS SUPPLY CURRENT vs. TEMPERATURE
150
VBIAS = 5V
145
140
135
130
125
120
115
-40
-15 10 35 60
TEMPERATURE (°C)
85
OUTPUT VOLTAGE ERROR vs. TEMPERATURE
1.00
VIN = 1.8V
0.75
0.50
0.25
ILOAD = 300mA
0
-0.25
ILOAD = 200mA
-0.50
ILOAD = 0mA
-0.75
-1.00
-40
-15 10 35 60
TEMPERATURE (°C)
85
DROPOUT VOLTAGE vs. OUTPUT CURRENT
200
VBIAS = 5V
150
100
50
0
0 50 100 150 200 250 300
OUTPUT CURRENT (mA)
SHORT-CIRCUIT CURRENT LIMIT
vs. INPUT VOLTAGE
800
700
600
500
400
300
200
100
0
1.50
2.50 3.50 4.50
INPUT VOLTAGE (V)
5.50
SHORT-CIRCUIT CURRENT LIMIT
vs. TEMPERATURE
700
650
600
550
500
-40
-15 10 35 60
TEMPERATURE (°C)
85
POWER-SUPPLY REJECTION RATIO (VIN)
vs. FREQUENCY
0
-10
VIN = 2.1V
VP-P = 0.6V
-20 ILOAD = 0
-30
-40
-50
-60
-70
-80
-90
-100
10
100 1k 10k 100k
FREQUENCY (Hz)
1M
_______________________________________________________________________________________ 5
5 Page 
Low-Voltage, Low-Dropout Linear Regulators
with External Bias Supply
350
MAXIMUM CONTINUOUS CURRENT
300
250 TA = +25°C
200 TA = +50°C
150 TA = +70°C
100
50
TJ = +150°C
0
012345
INPUT-OUTPUT DIFFERENTIAL VOLTAGE (V)
Figure 5. Power Operating Region—Maximum Output Current
vs. Supply Voltage
The UVLO circuitry monitors VBIAS 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 10µF or greater ceramic
capacitor. Bypass BIAS to ground with a 0.1µF ceramic
capacitor for normal operation in most applications.
Output Capacitor
Bypass OUT to ground with a low-ESR ceramic capaci-
tor greater than 10µF. The ESR must be less than
35mΩ. Choose an output capacitor to maintain the
required output voltage tolerance during a load step.
The change in output voltage is,
∆V = I ESR +
∆t
COUT
where I is the load current, COUT is the output capaci-
tance, and ∆t is the duration of the load step.
Noise, PSRR, and Transient Response
The MAX1982/MAX1983 operate with low-dropout volt-
age 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.
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.
Input/Output (Dropout) Voltage
A regulator’s minimum input-to-output voltage differen-
tial (dropout voltage) determines the lowest usable sup-
ply voltage. In battery-powered systems, the dropout
voltage determines the useful end-of-life battery volt-
age. Because the MAX1982/MAX1983 use an N-chan-
nel pass transistor, the dropout voltage is a function of
the drain-to-source on-resistance (RDS(ON) = 1Ω max)
multiplied by the load current (see the Typical
Operating Characteristics):
VDROPOUT = VIN − VOUT = RDS(ON) × IOUT
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 essen-
tial. 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.
Chip Information
TRANSISTOR COUNT: 430
PROCESS: BiCMOS
______________________________________________________________________________________ 11
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