Maxim MAX1806 500ma, low-voltage linear regulator in umax Datasheet

19-2018; Rev 0; 4/01
500mA, Low-Voltage Linear Regulator in µMAX
Applications
Features
♦ Guaranteed 500mA Output Current
♦ Output Down to 0.8V
♦ Low 175mV Dropout at 500mA
♦ ±1% Output Voltage Accuracy
Preset at 0.8V, 1.5V, 1.8V, 2.5V, or 3.3V
Adjustable from 0.8V to 4.5V
♦ Power-OK Output
♦ Low 210µA Ground Current
♦ 0.02µA Shutdown Current
♦ Thermal Overload Protection
♦ Output Current Limit
♦ Tiny 1.3W, 8-Pin Power-µMAX Package
Ordering Information
PART
MAX1806EUA_ _
TEMP. RANGE
PIN-PACKAGE
-40°C to +85°C
8 Power-µMAX
Notebook Computers
Cellular and Cordless Telephones
Selector Guide
PDAs
PART AND SUFFIX
Palmtop Computers
MAX1806EUA33
VOUT (V)
TOP MARK
3.3
AAAG
AAAH
Base Stations
MAX1806EUA25
2.5
USB Hubs
MAX1806EUA18
1.8
AAAI
Docking Stations
MAX1806EUA15
1.5
AAAJ
MAX1806EUA08
0.8
AAAK
Pin Configuration
Typical Operating Circuit
VIN
+2.25V TO +5.5V
VOUT
0.8V TO 4.5V
IN
NC
CIN
1µF
COUT
10µF
RPOK
100kΩ
MAX1806
ON
SHDN
POK
OFF
SET
TOP VIEW
OUT
GND
IN 1
8
OUT
7
OUT
3
6
SET
SHDN 4
5
GND
IN 2
MAX1806
TO
µC
POK
µMAX
________________________________________________________________ Maxim Integrated Products
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
MAX1806
General Description
The MAX1806 low-dropout linear regulator operates
from a +2.25V to +5.5V supply and delivers a guaranteed 500mA load current with low 175mV dropout. The
high-accuracy (±1%) output voltage is preset at an
internally trimmed voltage (see Selector Guide) or can
be adjusted from +0.8V to +4.5V with an external resistive-divider.
An internal PMOS pass transistor allows low 210µA
supply current, making this device ideal for portable
equipment such as personal digital assistants (PDAs),
cellular phones, cordless phones, and other equipment, including base stations and docking stations.
Other features include an active-low, power-OK output
that indicates when the output is out of regulation, a
0.02µA shutdown mode, short-circuit protection, and
thermal shutdown protection. The MAX1806 comes in a
miniature 1.3W, 8-pin power-µMAX package with a
metal pad on the underside of the package.
MAX1806
500mA, Low-Voltage Linear Regulator in µMAX
ABSOLUTE MAXIMUM RATINGS
IN, SHDN, POK, SET to GND ...................................-0.3V to +6V
OUT to GND ................................................-0.3V to (VIN + 0.3V)
Output Short-Circuit Duration.....................................Continuous
Continuous Power Dissipation (TA = +70°C)
8-Pin Power-µMAX (derate 17mW/°C above +70°C) .......1.3W
Operating Temperature .......................................-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(SETPOINT) + 500mV or VIN = +2.25V whichever is greater, SET = GND, 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
TA = +85°C, IOUT = 1mA to 500mA
TA = 0°C to +85°C, IOUT = 1mA to 500mA,
VIN > VOUT + 0.5V
Adjustable Output Voltage
SET Voltage Threshold
(Adjustable Mode)
VSET
Maximum Output Current
IOUT
Short-Circuit Current Limit
ILIM
Ground-Pin Current
ISET
IQ
Dropout Voltage (Note 1)
MAX
UNITS
1.85
5.5
V
2.0
2.15
V
-1
+1
-1.5
+1.5
-3
+3
0.8
4.5
TA = +85°C, IOUT = 100mA
790
810
TA = +85°C, IOUT = 1mA to 500mA
786
814
TA = 0°C to +85°C, IOUT = 1mA to 500mA,
VIN > VOUT + 0.5V
774
800
VOUT = 0V
VSET = +0.8V
mV
700
1400
2300
mA
35
80
125
mV
+100
nA
-100
210
IOUT = 500mA
575
400
µA
VOUT = +2.25V
259
384
VOUT = +2.8V
201
315
VOUT = +4.0V
147
255
0
0.125
%/V
35
ppm/mA
Line Regulation
∆VLNR
VIN from (VOUT + 100mV) to 5.5V, ILOAD = 5mA
Load Regulation
∆VLDR
IOUT = 1mA to 500mA
15.5
10Hz to 1MHz, COUT = 10µF (ESR < 0.1Ω)
300
SHDN = GND, VIN = 5.5V
0.02
Output Voltage Noise
V
mARMS
IOUT = 1mA
IOUT = 500mA
%
826
500
SET Dual Mode™ Threshold
SET Input Bias Current
TYP
2.25
Rising, 40mV hysteresis
TA = +85°C, IOUT = 100mA
Output Voltage Accuracy
(Preset Mode)
MIN
mV
µVRMS
SHUTDOWN
Shutdown Supply Current
SHDN Input Threshold
IOFF
VIH
1.6
0.6
VIL
SHDN Input Bias Current
I SHDN
SHDN = GND or IN
10
Startup Time
TSTART
COUT = 10µF, time from SHDN high to POK high
40
Dual Mode is a trademark of Maxim Integrated Products, Inc.
2
5
_______________________________________________________________________________________
100
µA
V
nA
µs
500mA, Low-Voltage Linear Regulator in µMAX
(VIN = VOUT(SETPOINT) + 500mV or VIN = +2.25V whichever is greater, SET = GND, 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
5
50
mV
5.5
V
100
nA
96
%
POWER-OK
POK Output Low Voltage
VOL
Operating Voltage Range for
Valid POK Output
Sinking 2mA
Sinking 100µA
1.0
Output High-Leakage Current
VPOK = +5.5V
Threshold
Rising edge, referred to VOUT(NOMINAL)
90
93
THERMAL PROTECTION
Thermal Shutdown Temperature
TSHDN
170
°C
Thermal Shutdown Hysteresis
∆TSHDN
20
°C
ELECTRICAL CHARACTERISTICS
(VIN = VOUT(SETPOINT) + 500mV or VIN = +2.25V whichever is greater, SET = GND, SHDN = IN, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
Input Voltage
SYMBOL
CONDITIONS
VIN
MIN
5.5
V
2.15
V
-4
+4
%
0.8
4.5
V
IOUT = 1mA to 500mA
766
834
mV
Rising, 40mV hysteresis
Output Voltage Accuracy
(Preset Mode)
VOUT
IOUT = 1mA to 500mA
Adjustable Output Voltage
SET Voltage Threshold
(Adjustable Mode)
VSET
Maximum Output Current
IOUT
Short-Circuit Current Limit
ILIM
VOUT = 0V
700
ISET
VSET = +0.8V
500
Threshold
SET Input Bias Current
Ground-Pin Current
IQ
Dropout Voltage (Note 1)
UNITS
2.25
VUVLO
SET Dual
MAX
1.85
Input Undervoltage Lockout
Mode™
TYP
mARMS
2500
mA
35
125
mV
-100
+100
nA
400
µA
IOUT = 1mA
IOUT = 500mA
VOUT = +2.25V
259
384
VOUT = +2.8V
201
315
VOUT = +4.0V
147
255
Line Regulation
∆VLNR
VIN from (VOUT + 100mV) to 5.5V, ILOAD = 5mA
Load Regulation
∆VLDR
-0.175
mV
+0.175
%/V
IOUT = 1mA to 500mA
35
ppm/mA
IOFF
SHDN = GND, VIN = 5.5V
5
µA
VIH
2.5V < VIN < 5.5V
VIL
2.5V < VIN < 5.5V
0.6
I SHDN
SHDN = GND or IN
100
SHUTDOWN
Shutdown Supply Current
SHDN Input Threshold
SHDN Input Bias Current
1.6
V
nA
_______________________________________________________________________________________
3
MAX1806
ELECTRICAL CHARACTERISTICS (continued)
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VOUT(SETPOINT) + 500mV or VIN = +2.25V whichever is greater, SET = GND, SHDN = IN, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
50
mV
5.5
V
100
nA
97
%
POWER-OK
POK Output Low Voltage
VOL
Sinking 2mA
Operating Voltage Range for
Valid POK Output
Sinking 100µA
1.0
Output High-Leakage Current
VPOK = +5.5V
Threshold
Rising edge, referred to VOUT(NOMINAL)
89
Note 1: Dropout voltage is defined as VIN - VOUT, when VOUT is 100mV below the value of VOUT and when VIN = VOUT(NOM) +0.5V.
For 2.25V ≤ VOUT ≤ 4.0V, dropout voltage limits are linearly interpolated from the values listed. For VOUT < 4.0V, dropout
voltage limit is equal to the value for VOUT = 4.0V.
Note 2: Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(MAX1806EUA33, VIN = VOUT + 500mV, SHDN = IN, CIN = 1µF, COUT = 10µF, TA = +25°C, unless otherwise noted.)
1.0
0.5
3.29
3.28
3.27
3.25
LOAD CURRENT (mA)
DROPOUT VOLTAGE vs. LOAD CURRENT
DROPOUT VOLTAGE vs.
OUTPUT VOLTAGE
250
TA = +25°C
200
150
100
TA = -40°C
0.26
0.24
0.22
0.20
0.18
0.14
0
0
100 200 300 400 500 600 700 800
LOAD CURRENT (mA)
2.0
2.5
3.0
3.5
OUTPUT VOLTAGE (V)
10
35
60
85
GROUND-PIN CURRENT vs.
INPUT VOLTAGE
0.16
50
4
0.28
DROPOUT VOLTAGE (V)
TA = +85°C
300
-15
TEMPERATURE (°C)
MAX1806 toc05
MAX1806 toc04
350
-40
100 200 300 400 500 600 700 800
INPUT VOLTAGE (V)
400
3.30
3.28
0
4.0
4.5
GROUND-PIN CURRENT (µA)
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
3.31
3.29
3.26
0
3.32
600
550
500
450
400
350
300
250
200
150
100
50
0
IOUT = 500mA
MAX1806 toc06
1.5
3.30
VIN = VOUT + 500mV
IOUT = 0
3.33
OUTPUT VOLTAGE (V)
3.31
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
IOUT = 500mA
2.0
OUTPUT VOLTAGE vs. TEMPERATURE
3.34
MAX1806 toc02
MAX1806 toc01
IOUT = 0mA
3.0
2.5
OUTPUT VOLTAGE vs. LOAD CURRENT
3.32
MAX1806 toc03
OUTPUT VOLTAGE vs. INPUT VOLTAGE
3.5
DROPOUT VOLTAGE (mV)
MAX1806
500mA, Low-Voltage Linear Regulator in µMAX
IOUT = 0mA
2.0
2.5
3.0
3.5
4.0
4.5
INPUT VOLTAGE (V)
_______________________________________________________________________________________
5.0
5.5
6.0
500mA, Low-Voltage Linear Regulator in µMAX
GROUND-PIN CURRENT vs.
LOAD CURRENT
VIN = 3.8V
300
250
200
190
-50
-40
180
170
160
-10
100 200 300 400 500 600 700 800
-40
-15
LOAD CURRENT (A)
10
35
60
0.01
85
0.1
1
10
100
1000
FREQUENCY (kHz)
TEMPERATURE (°C)
OUTPUT SPECTRAL NOISE DENSITY
vs. FREQUENCY
OUTPUT NOISE DC TO 1MHz
COUT = 10µF
IOUT = 50mA
MAX1806 toc10
MAX1806 toc11
10
OUTPUT SPECTRAL NOISE DENSITY (µV/√Hz)
COUT = 10µF
IOUT = 50mA
0
150
1
VOUT
1mV/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
MAX1806 toc13
100
MAX1806 toc12
0
-30
-20
150
100
MAX1806 toc09
-60
MAX1806 toc08
VIN = VOUT + 500mV
IOUT = 0
PSRR (dB)
350
GROUND-PIN CURRENT (µA)
VIN = 5.5V
REGION OF COUT ESR
GROUND-PIN CURRENT (µA)
450
400
200
MAX1806 toc07
500
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
GROUND-PIN CURRENT vs.
TEMPERATURE
IOUT
200mA/div
10
COUT = 10µF
1
VOUT
20mV/div
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
FREQUENCY (kHz)
_______________________________________________________________________________________
5
MAX1806
Typical Operating Characteristics (continued)
(MAX1806EUA33, VIN = VOUT + 500mV, SHDN = IN, CIN = 1µF, COUT = 10µF, TA = +25°C, unless otherwise noted.)
MAX1806
500mA, Low-Voltage Linear Regulator in µMAX
Typical Operating Characteristics (continued)
(MAX1806EUA33, VIN = VOUT + 500mV, SHDN = IN, CIN = 1µF, COUT = 10µF, TA = +25°C, unless otherwise noted.)
LOAD-TRANSIENT RESPONSE
NEAR DROPOUT
LINE-TRANSIENT RESPONSE
MAX1806 toc14
MAX1806 toc15
6V
VIN
1V/div
IOUT
200mA/div
3V
VOUT
50mV/div
VIN = VOUT + 100mV
CIN = 10µF
ROUT = 660Ω TO
6.6Ω (5mA TO 500mA)
VOUT
10mV/div
10µs/div
200µs/div
POK WAVEFORM
SHUTDOWN WAVEFORM
MAX1806 toc17
MAX1806 toc16
5V
2V
VSHDN
1V/div
VIN
2V/div
0
0
3V
VOUT
2V/div
0
VOUT
1V/div
VPOK
2V/div
0
0
ROUT = 6.6Ω (500mA)
ROUT = 66Ω (50mA)
200µs/div
20µs/div
Pin Description
PIN
6
NAME
FUNCTION
1, 2
IN
Regulator Input. Supply voltage can range from +2.25V to +5.5V. Bypass with a 1µF capacitor to GND (see
Capacitor Selection and Regulation Stability). Connect both input pins together externally.
3
POK
Open-Drain, Active-Low Power-OK Output. POK remains low while the output voltage (VOUT) is below the
POK threshold. Connect a 100kΩ pullup resistor from POK to OUT.
4
SHDN
Active-Low Shutdown Input. A logic low at SHDN reduces supply current to 0.02µA. In shutdown, the POK
output is low. Connect SHDN 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 SET to GND for preset output. Connect an external resistive voltage-divider
from OUT to SET to set the output voltage between 0.8V and 4.5V. The SET regulation voltage is 800mV.
7, 8
OUT
Regulator Output. OUT sources up to 500mA. Bypass OUT with a 10µF low-ESR capacitor to GND.
Connect both OUT pins together externally.
_______________________________________________________________________________________
500mA, Low-Voltage Linear Regulator in µMAX
The MAX1806 is a low-dropout, low-quiescent-current
linear regulator. The device supplies loads up to
500mA and is available with preset output voltages. As
illustrated in Figure 1, the MAX1806 includes a 0.8V reference, error amplifier, P-channel pass transistor, and
internal feedback voltage-divider.
The reference is connected to the error amplifier, which
compares it 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
increasing the output voltage. If the feedback voltage is
too high, the pass-transistor gate is pulled up, allowing
less current to pass to the output.
The output voltage is fed back through either an internal resistive voltage-divider connected to OUT or an
external resistor network connected to SET. The dualmode comparator examines VSET and selects the feedback path. If VSET is below 35mV, the internal feedback
path is used, and the output is regulated to the factorypreset voltage. Additional blocks include an output current limiter, thermal sensor, and shutdown logic.
Internal P-Channel Pass Transistor
The MAX1806 features a 0.4Ω P-channel MOSFET pass
transistor. Unlike similar designs using PNP pass transistors, P-channel MOSFETs require no base drive,
which reduces operating current. PNP-based regulators also waste considerable current in dropout when
the pass transistor saturates, and use high base-drive
currents under large loads. The MAX1806 does not suffer from these problems.
Output Voltage Selection
The MAX1806’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
MAX1806EUA33 has a preset 3.3V output voltage. The
output voltage may also be adjusted by connecting a
voltage-divider from OUT to SET (Figure 2). Select R2 in
the 25kΩ to 100kΩ range. Calculate R1 with the following equation:
R1 = R2 [(VOUT / VSET) - 1]
where VSET = 0.8V, and VOUT may range from 0.8V
to 4.5V.
Shutdown
Drive SHDN low to enter shutdown. During shutdown,
the output is disconnected from the input, and supply
current drops to 0.02µA. When in shutdown, POK pulls
low. 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.
Power-OK Output
The POK output pulls low when OUT is less than 93% of
the nominal regulation voltage. Once OUT exceeds
93% of the nominal voltage, POK goes high impedance. POK is an open-drain N-channel output. To
obtain a logic voltage output, connect a pullup resistor
from POK to OUT. A 100kΩ resistor works well for most
applications. POK can be used to signal a microcontroller (µC), or drive an external LED to indicate power
failure. When the MAX1806 is shutdown, POK is held
low independent of the output voltage. If unused, leave
POK grounded or unconnected.
Current Limit
The MAX1806 monitors and controls the pass transistor’s gate voltage, limiting the output current to 1.4A
(typ). 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 MAX1806. 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 MAX1806 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 MAX1806’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 ✕ (VIN V OUT ). The maximum allowed power dissipation is
1.3W or:
PMAX = (TJ(MAX) - TA) / (θJC + θCA)
where TJ - TA is the temperature difference between the
MAX1806 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 MAX1806 package features an exposed thermal pad on its underside. This
pad lowers the package’s thermal resistance by provid-
_______________________________________________________________________________________
7
MAX1806
Detailed Description
MAX1806
500mA, Low-Voltage Linear Regulator in µMAX
VIN
+2.25V TO +5.5V
IN
CIN
1µF
IN
THERMAL
SENSOR
MOSFET
DRIVER WITH
ILIM
PRESET MODE
OUT
ON
VOUT
0.8V TO 3.3V
SHDN
OUT
OFF
SHUTDOWN
LOGIC
COUT
10µF
VREF
0.8V
ERROR
AMPLIFIER
LOGIC SUPPLY
VOLTAGE (VOUT)
RPOK
100kΩ
MAX1806
POK
TO
µC
SET
93% VREF
80mV
GND
Figure 1. Functional Diagram
ing a direct heat conduction path from the die to the PC
board. 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 MAX1806 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 is within the limits outlined.
output capacitors. 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 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 MAX1806 as possible.
Applications Information
The MAX1806 is designed to operate with low dropout
voltages and low quiescent currents, 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 passivefiltering techniques. The MAX1806 load-transient
Capacitor Selection and Regulator
Stability
Connect a 1µF capacitor between IN and ground and a
10µF low equivalent series resistance (ESR) capacitor
between OUT and ground. 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
8
Noise, PSRR, and Transient Response
_______________________________________________________________________________________
500mA, Low-Voltage Linear Regulator in µMAX
MAX1806
0.8
IN
VOUT
0.8V
OUT
VIN
+2.25V TO +5.5V
VOUT
IN
CIN
1µF
OUT
COUT
10µF
MAX1806
R1
ON
SHDN
CONTINUOUS CURRENT LIMIT
-1
0.7
MAXIMUM OUTPUT CURRENT (A)
R1 = R2
0.6
TA = +50°C
0.5
0.4
TA = +85°C
TA = +70°C
0.3
TYPICAL VDROPOUT LIMIT
0.2
POWER-µMAX PACKAGE OPERATING
REGION AT TJ(MAX) = +150°C
0.1
SET
OFF
0
0
R2
POK
GND
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
INPUT-OUTPUT VOLTAGE DIFFERENTIAL (V)
Figure 3. Power Operating Regions: Maximum Output Current
vs. Supply Voltage
Figure 2. Adjustable Output Using External Feedback Resistors
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 overshoot for a step change in the load current from 5mA to 500mA is 40mV. 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 MAX1806 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) ✕ IOUT
Chip Information
TRANSISTOR COUNT: 949
_______________________________________________________________________________________
9
500mA, Low-Voltage Linear Regulator in µMAX
8L, µMAX, EXP PAD.EPS
MAX1806
Package Information
Note: The MAX1806 has on exposed thermal pad on the bottom side of the package.
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