19-3374; Rev 0; 7/04
500mA LDO Linear Regulators with
Current-Limiting Switch
The MAX4836/MAX4837 family of low-dropout (LDO)
linear regulators feature an accurate current-limiting
switch with an integrated FLAG or RESET function. These
devices operate from 2.5V to 5.5V and deliver up to
500mA of load current at a preset output voltage. Preset
output voltage levels are 1.8V/2.5V/2.8V/3.0V/3.3V.
The MAX4836/MAX4837 offer a programmable softstart control function to eliminate false reset during
startup. The MAX4836 provides a FLAG function to notify the system when the load current exceeds the limit.
The MAX4837 provides a RESET function to notify the
system when the output drops below the threshold.
Additionally, reverse-current protection prevents current flowing from the output to the input. Other features
include a low 90µA quiescent current, a 0.1µA shutdown current.
The MAX4836/MAX4837 are available in space-saving
6-pin SOT23 and TDFN packages. Each device is specified over the -40°C to +85°C extended temperature
range. Contact factory for other programmed output voltage versions from 1.5V to 3.3V in 100mV increments.
For pin-compatible 100mA versions of this device, refer
to the MAX4832/MAX4833. For pin-compatible 250mA
versions of this device, refer to the MAX4834/MAX4835.
Applications
SDIO Ports and Devices
Notebook Computers
USB Ports and Devices
Cell Phones
PDAs and Palmtop Devices
GPS Systems
Pin Configurations
TOP VIEW
IN
1
GND
2
SHDN
3
MAX4836/MAX4837
EXPOSED PADDLE
6
OUT
5
SS
4
RESET
(FLAG)
Features
♦ Guaranteed Minimum 500mA Load Current
♦ Accurate Current Limit
♦ Preset Output Voltages: 1.8V/2.5V/2.8V/3.0V/3.3V
♦ 2.5V to 5.5V Supply Voltage Range
♦ Adjustable Soft-Start
♦ Low Dropout Voltage
♦ Thermal Shutdown
♦ Reverse-Current Protection
♦ Shutdown Output Discharge (MAX4837)
♦ Low 90µA Supply Current
♦ Ultra-Low 0.1µA Shutdown Current
♦ FLAG and Latch Off (MAX4836) or RESET
(MAX4837)
♦ Tiny SOT23 and TDFN (3mm x 3mm) Packages
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX4836EUTxy_-T*
-40°C to +85°C
6 SOT23-6
MAX4836ETTxy_-T
-40°C to +85°C
6 TDFN-6
MAX4837EUTxy_dd-T*
-40°C to +85°C
6 SOT23-6
MAX4837ETTxy_dd-T
-40°C to +85°C
6 TDFN-6
Note: “xy” are placeholders for the output voltage levels of the
devices. Insert the values found in Table 1 at the end of this document in the place of “xy”. The “_” is a placeholder for either the
RESET or the FLAG feature. Insert “B” in the place of “_” for
RESET and “C” for FLAG. “dd” is a placeholder for the reset
timeout period. Insert the values found in Table 2 in the place of
“dd.” For example, MAX4837EUT18BD2 has a 1.8V output voltage, RESET feature, and a 30ms reset timeout period. Note that
“dd” applies only to the devices with RESET option and does not
apply to the devices with FLAG option. For devices with the
FLAG option, leave dd blank. Standard versions require a minimum order increment of 2.5k units. Nonstandard versions must
be ordered in 10k unit increments. Contact factory for availability.
*Future product—contact factory for availability.
Tables 1 and 2 and Selector Guide appear at end of data
sheet.
TDFN
( ) MAX4836ETTxyC ONLY.
Pin Configurations continued at end of data sheet.
________________________________________________________________ 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
MAX4836/MAX4837
General Description
MAX4836/MAX4837
500mA LDO Linear Regulators with
Current-Limiting Switch
ABSOLUTE MAXIMUM RATINGS
IN, SHDN, FLAG, OUT to GND ................................-0.3V to +6V
RESET to GND .........................................-0.3V to (VOUT + 0.3V)
SS to GND ...................................................-0.3V to (VIN + 0.3V)
IN to OUT ...............................................................................±6V
OUT Short Circuit to GND ..........................................Continuous
All Pins ESD Handling (Human Body Model).........................2kV
Continuous Power Dissipation (TA = +70°C)
6-Pin SOT23 (derate 9.1mW/°C above +70°C)................727mW
6-Pin TDFN (derate 24.4mW/°C above +70°C) ..........1951.2mW
Operating Temperature Range ...........................-40°C to +85°C
Operating Junction Temperature Range ...........-40°C to +125°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 + 1V, SHDN = IN, COUT = 3.3µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
Operating Voltage
Input Undervoltage Lockout
Threshold
SYMBOL
CONDITIONS
VIN
VUVLO
VIN rising
MIN
MAX
UNITS
2.5
5.5
V
2.00
2.25
V
Input Undervoltage Lockout
Threshold Hysteresis
Quiescent Current
50
IQ
Dropout Voltage (Note 2)
SHDN = IN, IOUT = 0
90
SHDN = IN, IOUT = 0,
VUVLO < VIN < VOUT (nominal)
150
SHDN = GND, IOUT = 0
0.1
IOUT = 500mA
TA = +25°C
IOUT = 1mA to 500mA, TA = -40°C to +85°C
IOUT
VOUT = 0V
Reverse Current at VIN
VOUT = 5.5V, VIN = 0V to VOUT
150
µA
2
300
330
-1.3
+1.3
-2
+2
CSS = 0.01µF
CSS = 0.1µF
mV
%VNOM
mA
540
CSS = not connected
tSS
mV
500
Output Current Limit
Soft-Start Time (Note 3)
200
TA = -40°C to +85°C
IOUT = 1mA to 500mA, TA = +25°C
Output Voltage Accuracy
Output Current
TYP
660
mA
µA
0.1
2
0.5
1
2.0
4
10
15
40
100
TA = +25°C
-0.04
+0.02
TA = -40°C to +85°C
-0.05
+0.03
ms
150
+0.065 %VNOM/
V
+0.08
Line Regulation (Note 4)
VOUT + 0.5V < VIN <
5.5V, ILOAD = 100µA
Load Regulation
100µA < ILOAD < 500mA, VIN = VOUT + 1V
1.3
%VNOM
Output Noise
10Hz to 100kHz, CSS = 0.01µF
70
µVRMS
SHDN = GND
900
Ω
SHUTDOWN INPUT (SHDN)
OUT Discharge Resistance in
Shutdown (MAX4837)
SHDN Input-Voltage High
VIH
SHDN Input-Voltage Low
VIL
1.4
0.5
SHDN Input Hysteresis
SHDN Input Leakage Current
2
V
30
SHDN = IN or GND
-100
_______________________________________________________________________________________
V
mV
+100
nA
500mA LDO Linear Regulators with
Current-Limiting Switch
(VIN = VOUT + 1V, SHDN = IN, COUT = 3.3µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
0.85 x
VOUT
0.875 x
VOUT
0.90 x
VOUT
V
RESET OUTPUT (MAX4837)
RESET Threshold
VRESET
OUT Drop to RESET Delay
(Note 5)
RESET Timeout Period
tOR
tRESET
RESET Output-Voltage Low
35
D1 timing option
2.5
3.75
5.0
D2 timing option
20
30
40
D3 timing option
150
225
300
D4 timing option
1200
1800
2400
VOUT ≥ 1.0V, ISINK = 50µA, RESET asserted
0.3
VOUT ≥ 1.5V, ISINK = 3.2mA, RESET
asserted
0.4
VOUT ≥ 2.0V, ISOURCE ≤ 500µA,
RESET deasserted
RESET Output-Voltage High
µs
0.8 x
VOUT
ms
V
V
FLAG OUTPUT (MAX4836)
Blanking Time (Note 6)
tBLANK
VOUT + 1V ≤ VIN ≤ 5.5V, OUT = GND
5
10
17
ms
0.4
V
1
µA
Open-Drain FLAG OutputVoltage Low
ISINK = 3.2mA, FLAG asserted, VOUT ≥ 1.5V
Open-Drain FLAG Leakage
Current
VFLAG = 5.5V
0.01
Junction temperature rising
+165
°C
15
°C
THERMAL PROTECTION
Thermal-Shutdown Temperature
Thermal-Shutdown Hysteresis
Note 1: Parts are 100% tested at +25°C. Limits across the full temperature range are guaranteed by design and correlation over the
specified temperature range.
Note 2: The dropout voltage is measured from VIN to VOUT when VOUT is 2% below its nominal value. The nominal output voltage is
measured from VOUT to GND when VIN is 1V greater than VOUT. Defined only for VOUT ≥ 2.5V.
Note 3: Soft-start time is defined as the time required for the output to rise from 10% of its nominal value to 90% of its nominal value.
Note 4: For VOUT < 2V, VIN must be above 2.5V.
Note 5: This is the maximum time OUT can be out of tolerance before a reset is issued. It is implemented to ensure that momentary
output glitches do not trigger a reset condition.
Note 6: In startup mode, the blanking time counter is not started until the soft-start time has elapsed. The total time from startup to
FLAG issued is tSS + tBLANK.
_______________________________________________________________________________________
3
MAX4836/MAX4837
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VIN = VOUT + 1V, SHDN = IN, COUT = 3.3µF, TA = +25°C, unless otherwise noted.)
TA = +85°C
100
TA = +85°C
700
TA = +25°C
IQ (µA)
IQ (µA)
500
60
TA = -40°C
TA = +25°C
TA = -40°C
400
300
40
75
PULSE DURATION (µs)
600
80
90
MAX4836 toc02
800
MAX4836 toc01
120
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
QUIESCENT CURRENT vs. INPUT VOLTAGE
(500mA LOAD)
RESET ASSERTS
ABOVE THIS LINE
MAX4836 toc03
QUIESCENT CURRENT vs. INPUT VOLTAGE
(NO LOAD)
60
45
30
200
15
100
VOUT = 1.5V
VOUT = 3.3V
0
0
0
1
2
3
4
5
6
0
1
2
3
4
5
VIN = 3.5V
VOUT = 2.5V
0
1
6
VIN (V)
RESET THRESHOLD OVERDRIVE (mV)
DROPOUT VOLTAGE vs. LOAD CURRENT
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
REGION OF STABLE COUT ESR
vs. LOAD CURRENT
VOUT = 3.3V
150
VOUT = 2V
COUT = 3.3µF
ILOAD = 20mA
-10
-20
90
30
-30
-40
0
100
200
300
-70
1
0
0.1
1
100
0
50 100 150 200 250 300 350 400 450 500
MAX4836 toc08
MAX4836 toc07
50
LOAD CURRENT (mA)
SOFT-START RESPONSE
(CSS = FLOATING)
OUTPUT NOISE vs. FREQUENCY
OUTPUT NOISE (µVRMS)
10
FREQUENCY (kHz)
LOAD CURRENT (mA)
VIN = 3V
VOUT = 1.8V
CSS = 10nF
ILOAD = 0
40
STABLE REGION
3
2
0.01
500
400
4
-60
-80
0
COUT = 3.3µF
5
-50
60
VOUT = 1.8V
6
COUT ESR (Ω)
PSRR (dB)
120
7
MAX4836 toc05
0
MAX4836 toc04
180
VIN
2V/div
30
20
tSS
VOUT
2V/div
10
VSS
1V/div
0
10
100
1k
10k
100k
2ms/div
FREQUENCY (Hz)
4
100
10
VIN (V)
MAX4836 toc06
20
DROPOUT VOLTAGE (mV)
MAX4836/MAX4837
500mA LDO Linear Regulators with
Current-Limiting Switch
_______________________________________________________________________________________
500mA LDO Linear Regulators with
Current-Limiting Switch
(VIN = VOUT + 1V, SHDN = IN, COUT = 3.3µF, TA = +25°C, unless otherwise noted.)
SOFT-START RESPONSE
(CSS = 0.01µF)
SOFT-START RESPONSE
(CSS = 0.1µF)
MAX4836 toc09
LOAD-TRANSIENT RESPONSE
VIN = 4.3V
VOUT = 3.3V
CIN = 0.1µF
COUT = 3.3µF
ILOAD: STEP FROM 10mA TO 100mA
BACK TO 10mA
VIN
2V/div
VIN
2V/div
tSS
VSS
1V/div
VSS
1V/div
100µs/div
20ms/div
2ms/div
LOAD-TRANSIENT RESPONSE
NEAR DROPOUT
LINE-TRANSIENT RESPONSE
RESET RESPONSE TO VIN
MAX4836 toc13
MAX4836 toc12
VIN = 3.4V
VOUT = 3.3V
CIN = 0.1µF
COUT = 3.3µF
ILOAD: STEP FROM 10mA TO 100mA
BACK TO 10mA
VOUT
50mV/div
AC-COUPLED
VOUT
2V/div
VOUT
2V/div
tSS
MAX4836 toc11
MAX4836 toc10
MAX4836 toc14
CSS = FLOATING
VOUT
50mV/div
AC-COUPLED
CIN = 0.1µF
COUT = 3.3µF
VOUT = 3.3V
ILOAD = 10mA
5V
VIN
500mV/div
4.5V
VIN
2V/div
VOUT
50mV/div
AC-COUPLED
VOUT
2V/div
tRESET
100µs/div
100µs/div
VRESET
2V/div
40ms/div
RESET RESPONSE TO SHUTDOWN
RESET RESPONSE TO VOUT
MAX4836 toc15
MAX4836 toc16
VIN = 3.5V, CSS = FLOATING
VIN = 3.5V, CSS = FLOATING
VSHDN
2V/div
VOUT
1V/div
VOUT
2V/div
tRESET
40ms/div
VRESET
1V/div
tRESET
VRESET
2V/div
40ms/div
_______________________________________________________________________________________
5
MAX4836/MAX4837
Typical Operating Characteristics (continued)
Typical Operating Characteristics (continued)
(VIN = VOUT + 1V, SHDN = IN, COUT = 3.3µF, TA = +25°C, unless otherwise noted.)
FLAG RESPONSE WHEN OUT IS
SHORTED TO GND > BLANKING TIME
(IN IS TOGGLED)
FLAG RESPONSE WHEN OUT IS
SHORTED TO GND < BLANKING TIME
MAX4836 toc17
FLAG RESPONSE WHEN OUT IS
SHORTED TO GND > BLANKING TIME
(SHDN IS TOGGLED)
MAX4836 toc18
VOUT
2V/div
MAX4836 toc19
VOUT
1V/div
tBLANK
VOUT
1V/div
VFLAG
2V/div
IOUT
200mA/div
VFLAG
2V/div
tBLANK
VIN
2V/div
VFLAG
5V/div
VSHDN
2V/div
FLAG CONNECTED TO LOGIC SUPPLY
FLAG CONNECTED TO LOGIC SUPPLY
1ms/div
10ms/div
10ms/div
STARTUP IN AN OVERLOAD CONDITION
(CSS NOT CONNECTED)
STARTUP IN AN OVERLOAD CONDITION
(CSS = 0.01µF)
NORMALIZED OUTPUT VOLTAGE
vs. TEMPERATURE
MAX4836 toc21
VIN
2V/div
tSS
tBLANK
2ms/div
VOUT = 2.5V
ILOAD = ILIMIT MAXIMUM
FLAG CONNECTED TO LOGIC SUPPLY
6
VOUT
2V/div
1.004
VIN
2V/div
tSS
tBLANK
VOUT
2V/div
VFLAG
2V/div
VFLAG
2V/div
VSS
1V/div
VSS
1V/div
4ms/div
VOUT = 2.5V
ILOAD = ILIMIT MAXIMUM
FLAG CONNECTED TO LOGIC SUPPLY
MAX4836 toc22
MAX4836 toc20
NORMALIZED TO +25°C
NORMALIZED OUTPUT VOLTAGE
MAX4836/MAX4837
500mA LDO Linear Regulators with
Current-Limiting Switch
1.002
ILOAD = 500mA
1.000
ILOAD = 100mA
0.998
ILOAD = 300mA
0.996
0.994
-40
-15
10
35
TEMPERATURE (°C)
_______________________________________________________________________________________
60
85
500mA LDO Linear Regulators with
Current-Limiting Switch
PIN
NAME
FUNCTION
SOT23
TDFN
1
1
IN
2
2
GND
Ground
SHDN
Active-Low Shutdown Input. Drive SHDN low to shutdown the regulator. Drive SHDN high or
connect to IN for normal operation.
3
3
Regulator Power Input. Bypass IN to GND with a 0.1µF ceramic capacitor. Install the bypass
capacitor as close to the device as possible.
Overcurrent Flag. Open-drain FLAG goes low when the device senses sustained current
FLAG
exceeding the current-limit threshold for a duration longer than the blanking time. FLAG is high
(MAX4836)
when SHDN is low or the device is in thermal shutdown.
4
4
5
5
SS
Soft-Start Control. Connect a capacitor, CSS, from SS to GND to program the output rise time at
startup. No capacitor from SS to GND gives 1ms output rise time at startup. See the soft-start
response time plots in the Typical Operating Characteristics.
6
6
OUT
Regulator Output. Bypass OUT to GND with a 3.3µF or larger ceramic capacitor. The capacitor’s
ESR should be less than 0.2Ω for stable operation.
—
EP
EP
Exposed Pad. EP is internally connected to GND. Externally connect EP to GND to provide a low
thermal resistance path from the IC junction to the PC board.
Active-Low Reset Output. Push-pull RESET goes low when the voltage at OUT is below the reset
RESET
threshold or when the voltage at OUT is greater than IN. RESET is low when SHDN is low or the
(MAX4837) device is in thermal shutdown. After the reset condition terminates, RESET remains low for the
duration of the reset timeout period.
Detailed Description
The MAX4836/MAX4837 are ultra-low quiescent current,
low-dropout linear regulators with an integrated current
limiter. These devices guarantee up to 500mA drive
capabilities and regulate the preset output voltage.
The MAX4836 has a flag output that asserts low when
the load current exceeds the current limit for more than
the blanking time (tBLANK). The MAX4837 has a reset
output that asserts low when the regulator output voltage is below the reset threshold voltage (V RESET ).
VRESET is 87.5% of the nominal output voltage. Figure 1
shows the simplified functional diagram and Figure 2
shows the typical application circuits.
FLAG Output (MAX4836)
The open-drain FLAG output goes low and the LDO’s
pass transistor is latched off when the current in the
pass transistor is at its output current limit for more than
the blanking time (tBLANK). Cycling IN or SHDN (high to
low to high) brings the device out of its latched-off state
and back into normal operation.
RESET Output (MAX4837)
The RESET output asserts when one of the following
conditions occurs:
• The input voltage (VIN) is below the input undervoltage lockout threshold (VUVLO).
• The output voltage (VOUT) is below the reset threshold (VRESET).
• SHDN is pulled low.
• The device is in thermal shutdown.
• When VOUT > VIN.
RESET remains low for the reset timeout period (tRESET)
after reset conditions are terminated. There are four
RESET timeout periods available as shown in the
Electrical Characteristics table. RESET is available in a
push-pull configuration as shown in the Selector Guide.
Shutdown
Pull SHDN low to shut down the LDO and reduce the
quiescent current consumption of the device from 90µA
to 0.1µA. In shutdown mode, the pass transistor, control circuit, and reference circuit are turned off. Connect
SHDN to a supply voltage greater than VIH to turn on
the LDO.
_______________________________________________________________________________________
7
MAX4836/MAX4837
Pin Description
MAX4836/MAX4837
500mA LDO Linear Regulators with
Current-Limiting Switch
THERMAL
PROTECTION
REVERSECURRENT
PROTECTION
IN
MAX4836/MAX4837
PASS
TRANSISTOR
OUT
ERROR
AMPLIFIER VSS
MAX4837 ONLY
900Ω
vFB
SWITCH
CLOSED IN
SHUTDOWN
OVERLOAD
PROTECTION
VREF
1.23V
SHDN
VREF
SWITCH OPEN
DURING SOFT-START
VREF
RESET
(FLAG)
VFB
RESET TIMEOUT
VSS = VREF
WHEN SOFT-START
IS COMPLETE
90% x VREF
1.23µA
VSS
SS
(BLANKING PERIOD)
1nF
GND
( ) MAX4836E_ _xyC ONLY.
Figure 1. Functional Diagram
IN
2.5V TO 5.5V
CIN
0.1µF
OUT
IN
COUT
3.3µF
VLOGIC
2.5V TO 5.5V
LOAD
COUT
3.3µF
MAX4836
TO µC
MAX4837
TO µC
SS
FLAG
OUT
CIN
0.1µF
SS
RESET
CSS
CSS
ON
ON
SHDN
OFF
SHDN
GND
OFF
GND
Figure 2. Typical Application Circuits
8
_______________________________________________________________________________________
LOAD
500mA LDO Linear Regulators with
Current-Limiting Switch
Reverse OUT to IN Current
When the output voltage is greater than the input voltage, the internal pass transistor turns off. To avoid
reverse-charging the input source, the current at IN is
guaranteed to be below 3µA when VOUT ≥ VIN.
Current Limit
The MAX4836/MAX4837 include an accurate internal
current-limiting circuit. OUT can be shorted to ground
indefinitely without damaging the part.
The MAX4836 latches off if the load current exceeds the
current limit for more than the blanking time (see the
FLAG Output section). During soft-start, the device does
not latch off to an overload condition. During an overload
condition, the MAX4837 holds the current at current limit
until the thermal limit is reached. Once the junction temperature reaches +165°C, thermal shutdown occurs.
Thermal Shutdown
When the junction temperature (TJ) exceeds +165°C,
the LDO’s pass transistor turns off allowing the junction
to cool. The LDO’s pass transistor turns on again after
the IC’s junction temperature cools by 15°C, resulting in
a pulsed output during continuous thermal-overload
conditions.
Soft-Start
During power-up, the soft-start ensures that the output
ramps up slowly reducing inrush current peaks. See
the soft-start response time plots in the Typical
Operating Characteristics. The soft-start time (tSS) is
given by the following equation:
tSS = CSS (ms)
where CSS is in nF.
A soft-start capacitor (CSS) of 10nF gives a 10ms tSS. A
1ms minimum soft-start time is fixed internally to ensure
that the output rises slowly even without any external
capacitor at SS pin to ground. The device is in soft-start
mode when either the voltage at IN or SHDN is cycled
high to low to high.
Applications Information
Capacitor Selection and Regulator
Stability
For stable operation over the full temperature range and
with load currents up to 500mA, use a 3.3µF (min)
ceramic output capacitor with an ESR
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