General Description
The MAX8633–MAX8636 offer low-dropout (LDO) volt-
age and ultra-low-power regulation in a subminiaturized
2mm x 2mm µDFN package. The devices operate from
a 2.7V to 5.5V supply and deliver up to 300mA from
each output, with a typical dropout voltage of 90mV at
100mA load current. Each device is designed with
internal p-channel MOSFET pass transistors to ensure a
low-quiescent supply current of 54µA (typical, both
LDOs on). Other features include low-noise operation
(MAX8634/MAX8636), output current limiting, and ther-
mal shutdown.
The MAX8633 features an open-drain, active-low
RESET output to monitor OUT2, eliminating external
components and adjustments. The MAX8633 asserts a
RESET signal (120ms minimum timeout) when VOUT2
drops below 87% of the nominal output voltage. The
MAX8634/MAX8636 feature a noise bypass input to the
internal reference for low output noise (45µVRMS typ).
The MAX8634/MAX8635 provide independent SHDN
inputs for disabling the regulators, while the MAX8633/
MAX8636 provide a single SHDN input for disabling
both regulators.
The MAX8633/MAX8635/MAX8636 have two logic
inputs that select one of nine preset output-voltage
combinations, eliminating external 1% resistors, as well
as inventory burden. The MAX8634 has one logic input
to select three output-voltage options.
The MAX8633–MAX8636 are available in an 8-pin, 2mm
x 2mm µDFN package for minimizing footprint, and an
8-pin, 3mm x 3mm TDFN package for higher power dis-
sipation. The devices are specified over the extended
temperature range (-40°C to +85°C). All packages are
lead free.
Applications
Cellular and Cordless Phones
PDAs and Digital Cameras
Small LCD Displays
Notebook Computers
Wireless LAN Cards
Handheld Instruments
Features
♦Pin-Programmable Output Voltages
♦300mA Output Current
♦Low 90mV Dropout at 100mA Load
♦Open-Drain, Active-Low RESET (MAX8633)
♦Low 45µVRMS Output Noise (MAX8634/MAX8636)
♦Low 54µA Quiescent Supply Current
♦Low < 1µA Maximum Shutdown Current
♦Output Current Limit
♦Thermal Shutdown
MAX8633–MAX8636
Dual 300mA Pin-Programmable LDO
Linear Regulators
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
MAX8633
IN
SHDN
OUT2
OUT2
GND
OUT1
RESET
P2
P1
COUT1
2.2μF
CIN
2.2μF
COUT2
2.2μF
INPUT
2.7V TO 5.5V
Typical Operating Circuits
19-0516; Rev 1; 9/08
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.
+
Denotes a lead-free/RoHS-compliant package.
Ordering Information continued at end of data sheet.
Pin Configurations and Selector Guide appear at end of
data sheet.
EVALUATION KIT
AVAILABLE
PART TEMP RANGE PIN-
PACKAGE
TOP
MARK
MAX8633ELA+ -40°C to +85°C 8 µDFN
2mm x 2mm AAH
MAX8633ETA+ -40°C to +85°C 8 TDFN
3mm x 3mm AOQ
MAX8634ELA+ -40°C to +85°C 8 µDFN
2mm x 2mm AAI
Typical Operating Circuits continued at end of data sheet.
MAX8633–MAX8636
Dual 300mA Pin-Programmable LDO
Linear Regulators
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN = 3.7V, SHDN = SHDN1 = SHDN2 = IN, P = P1 = P2 = GND, CIN = 2.2µF, COUT1 = 2.2µF, COUT2 = 2.2µF, CBP = 0.01µF, TA=
-40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
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.
(All voltages refer to GND, unless otherwise noted.)
IN ...........................................................................-0.3V to +6.0V
SHDN, SHDN1, SHDN2, RESET,
P, P1, P2, BP, OUT1, OUT2.....................-0.3V to (VIN + 0.3V)
Continuous Output Short-Circuit Duration..................Continuous
Continuous Power Dissipation (TA= +70°C)
8-Pin µDFN 2mm x 2mm
(derate 4.8mW/°C above +70°C).................................380mW
8-Pin TDFN 3mm x 3mm
(derate 23.8mW/°C above +70°C).............................1904mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input Voltage VIN 2.7 5.5 V
Input Undervoltage
Lockout VUVLO VIN rising; hysteresis = 95mV (typ) 2.15 2.25 2.35 V
IOUT_ = 0mA 54 75
IOUT_ = 100mA 60Ground Current IQ
IOUT_ = 10mA, dropout (Note 2) 60
µA
TA = +25°C 0.005 1
Shutdown Supply
Current IOFF SHDN_ = GND TA = +85°C 0.01 µA
OUT1, OUT2
IOUT_ = 70mA; TA = +25°C -0.7 +0.7
IOUT_ = 70mA -1 +1
Output Voltage
Accuracy (for Any
Output Voltage) IOUT_ = 0.1mA to 300mA; VIN = (VOUT_ + 0.5V) to
5.5V -1.8 +1.7
%
Current Limit ILIM OUT_ = 0V 400 500 600 mA
Drop-Out Voltage VIN - VOUT
VOUT_ = 2.8V (MAX8633);
VOUT_ = 2.85V (MAX8634/MAX8635/MAX8636);
IOUT_ = 100mA (Note 2)
90 200 mV
MAX8633
MAX8635 450
Output Noise f = 10Hz to 100kHz;
IOUT_ = 10mA MAX8634
MAX8636 45
µVRMS
f < 1kHz 60
Output AC Power-
Supply Rejection
Ratio
PSRR IOUT_ = 30mA
f < 10kHz 55
dB
MAX8633–MAX8636
Dual 300mA Pin-Programmable LDO
Linear Regulators
_______________________________________________________________________________________ 3
Note 1: All units are 100% tested at TA= +25°C. Limits over the operating temperature range are guaranteed by design.
Note 2: The dropout voltage is defined as VIN - VOUT_ when VOUT_ drops by 100mV from VOUT_ when measured at VIN = +3.7V.
Note 3: Connect P_ to IN or GND through a resistor less than 1kΩ.
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 3.7V, SHDN = SHDN1 = SHDN2 = IN, P = P1 = P2 = GND, CIN = 2.2µF, COUT1 = 2.2µF, COUT2 = 2.2µF, CBP = 0.01µF, 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
SHUTDOWN INPUTS (SHDN, SHDN1, AND SHDN2)
Input Voltage High VIH VIN = 2.7V to 5.5V 1.5
Input Voltage Low VIL VIN = 2.7V to 5.5V 0.5 V
TA = +25°C 0.1 1000
Input Bias Current ISHDN_ VIN = 2.7V to 5.5V;
VSHDN_ = GND or IN TA = +85°C1
nA
Turn-On Delay From SHDN = high to 87% of VOUT_;
IOUT_ = 70mA 90 µs
TRI-LEVEL INPUTS (P, P1, P2)
For high or low state 1
Ter m i nati on
Resi stance to IN or
G N D for S etti ng H i g h,
O p en, and Low S tates
IN = 2.7 to 5.5V
For open state 100
kΩ
Input Load
Capacitance for
Open State
Design guide only 50 pF
RESET
RESET High
Threshold Percent of nominal OUT2; OUT2 rising 84 87 90 %
RESET Threshold
Hysteresis Percent of nominal OUT2; OUT2 falling 4.5 %
IRESET = 20µA; VIN = 1.0V 10 100
RESET Output
Voltage Low IRESET = 500µA; VIN = 3.7V 5 100 mV
TA = +25°C 0.1 300
RESET Output High
Leakage Current ILEAK VRESET = VIN = 5.5V TA = +85°C1
nA
RESET Delay tRP From OUT2 rising to RESET rising 120 150 180 ms
THERMAL PROTECTION
Thermal-Shutdown
Threshold TSHDN +165 °C
Thermal-Shutdown
Hysteresis ΔTSHDN 15 °C
MAX8633–MAX8636
Dual 300mA Pin-Programmable LDO
Linear Regulators
4 _______________________________________________________________________________________
Typical Operating Characteristics
(VIN = 3.8V, P = P1 = P2 = GND, IOUT1, 2 = 70mA, COUT1 = 2.2µF, COUT2 = 2.2µF, CBP = 0.01µF, CIN = 2.2µF, and TA = +25°C,
unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(MAX8633ELA+)
MAX8633 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (μA)
54321
10
20
30
40
50
60
70
0
06
IOUT1 = IOUT2 = 70mA
IOUT1 = IOUT2 = 0mA
SUPPLY CURRENT vs. LOAD CURRENT
(MAX8635ELA+)
MAX8633 toc02
LOAD CURRENT (mA)
SUPPLY CURRENT (μA)
25020015010050
55
60
65
70
50
0 300
P1 = P2 = IN
SUPPLY CURRENT vs. TEMPERATURE
(MAX8633ELA+)
MAX8633 toc03
TEMPERATURE (°C)
SUPPLY CURRENT (μA)
603510-15
45
50
55
60
65
70
40
-40 85
IOUT1 = IOUT2 = 70mA
IOUT1 = IOUT2 = 0mA
DROPOUT VOLTAGE vs. LOAD CURRENT
(MAX8633ELA+)
MAX8633 toc04
LOAD CURRENT (mA)
DROPOUT VOLTAGE (V)
25020015010050
0.05
0.10
0.15
0.20
0.25
0.30
0
0 300
OUT1
DROPOUT VOLTAGE vs. OUT1 VOLTAGE
(MAX8633ELA+)
MAX8633 toc05
OUT1 VOLTAGE (V)
DROPOUT VOLTAGE (mV)
2.85
2.80
2.752.702.65
50
60
70
80
40
2.60 2.952.90
OUT1
P1 = P2 = IN
OUTPUT VOLTAGE ACCURACY
vs. TEMPERATURE (MAX8633ELA+)
MAX8633 toc06
TEMPERATURE (°C)
OUT1 VOLTAGE ACCURACY (%)
603510-15
-0.5
0
-1.5
-1.0
0.5
1.0
1.5
2.0
-2.0
-40 85
OUT1
PSRR vs. FREQUENCY
(MAX8636ELA+)
MAX8633 toc07
FREQUENCY (kHz)
PSRR (dB)
1010.1
30
40
10
20
50
60
70
0
0.01 100
ROUT1 = 100Ω
P1 = IN
P2 = GND
CHANNEL-TO-CHANNEL ISOLATION
vs. FREQUENCY (MAX8636ELA+)
MAX8633 toc08
FREQUENCY (kHz)
PSRR (dB)
1010.1
30
40
10
20
50
60
70
0
0.01 100
ROUT1 = 100Ω
OUTPUT SPECTRAL NOISE DENSITY
vs. FREQUENCY (MAX8636ELA+)
MAX8633 toc09
FREQUENCY (kHz)
NOISE DENSITY (nV/ Hz)
10 10010.1
100
1000
10,000
10
0.01 1000
OUT1
P1 = IN
P2 = GND
MAX8633–MAX8636
Dual 300mA Pin-Programmable LDO
Linear Regulators
_______________________________________________________________________________________ 5
Typical Operating Characteristics (continued)
(VIN = 3.8V, P = P1 = P2 = GND, IOUT1, 2 = 70mA, COUT1 = 2.2µF, COUT2 = 2.2µF, CBP = 0.01µF, CIN = 2.2µF, and TA = +25°C,
unless otherwise noted.)
OUTPUT NOISE DC TO 100kHz
(MAX8636ELA+)
MAX8633 toc10
1ms/div
50μV/div
LINE TRANSIENT RESPONSE
(MAX8633ELA+)
MAX8633 toc11
40μs/div
0
1V/div
10mV/div
VIN
AC
VOUT1
3.8V
4.8V
MAX8633
IOUT1 = 70mA
LOAD TRANSIENT
(MAX8633ELA+ OUT1 ILOAD = 1mA TO 70mA)
MAX8633 toc12
40μs/div
0
100mA/div
20mV/div
IOUT1
AC
VOUT1
1mA
70mA
MAX8633
VIN = 3.8V
LOAD TRANSIENT NEAR DROPOUT
(VIN = VOUT + 0.1V, MAX8633ELA+ OUT1)
MAX8633 toc13
40μs/div
0
100mA/div
20mV/div
IOUT1
AC
VOUT1
1mA
70mA
MAX8633
VIN = VOUT1 + 0.1V
RESET TIMING
(MAX8633ELA+)
MAX8633 toc14
40ms/div
0
0
5V/div
2V/div
0
2V/div
OUT1
MAX8633
RESET
SHDN
OUT1 AND OUT2 TURN-ON SEQUENCE
(MAX8633ELA+)
MAX8633 toc15
40μs/div
0
0
2V/div
2V/div
0
2V/div
OUT1
OUT2
MAX8633
P1 = P2 = GND
IOUT1 = IOUT2 = 70mA
SHDN
MAX8633–MAX8636
Dual 300mA Pin-Programmable LDO
Linear Regulators
6 _______________________________________________________________________________________
Pin Description
PIN
MAX8633 MAX8634 MAX8635 MAX8636 NAME FUNCTION
1111IN
Regulator Input. Supply voltage from 2.7V to 5.5V.
Bypass IN with a ceramic capacitor of at least 2.2µF to
GND (see the Capacitor Selection and Regulator
Stability section).
2——2SHDN
Shutdown Input, Active Low. Drive SHDN logic low to
shut down both regulators. Connect SHDN to IN or drive
logic high for normal operation (see the Power-On
Sequence (MAX8633/Max8636 Only) section).
—2 2—SHDN1
LDO1 Shutdown Input, Active Low. Drive SHDN1 logic
low to shut down OUT1. Connect SHDN1 to IN or drive
logic high for normal operation.
—3 5—SHDN2
LDO2 Shutdown Input, Active Low. Drive SHDN2 logic
low to shut down OUT2. Connect SHDN2 to IN or drive
logic high for normal operation.
3—3 3P2
Programming Input 2. The state of P1 and P2 selects
one of nine output-voltage options (see Tables 1, 3).
4—4 4P1
Programming Input 1. The state of P1 and P2 selects
one of nine output-voltage options (see Tables 1, 3).
—4———P
Programming Input. The state of P selects one of three
output-voltage options for the MAX8634 (see Table 2).
5———RESET
Reset Output, Active Low, Open Drain. RESET goes high
impedance 120ms (min) after VOUT2 rises above 87% of
the nominal output voltage. RESET is forced logic low
when VOUT2 is below 82.5% of the nominal output
voltage. Connect RESET to OUT1, OUT2, or another
voltage of VIN or lower with a pullup resistor.
—5—5BP
Reference Noise Bypass. Bypass BP to GND with a
0.01µF ceramic capacitor to reduce output noise.
6 6 6 6 GND Ground
7 7 7 7 OUT2
Regulator 2 Output. Guaranteed 300mA output current
(see the Calculating Maximum Output Power section).
Bypass OUT2 with a ceramic capacitor of at least 2.2µF
to GND (see the Capacitor Selection and Regulator
Stability section).
8 8 8 8 OUT1
Regulator 1 Output. Guaranteed 300mA output current
(see the Calculating Maximum Output Power section).
Bypass OUT1 with a ceramic capacitor of at least 2.2µF
to GND (see the Capacitor Selection and Regulator
Stability section).
EP* EP* EP* EP* EP
Exposed Paddle. Solder the exposed paddle to a large
pad or circuit-board ground plane to increase thermal
dissipation.
*
TDFN package only.
MAX8633–MAX8636
Dual 300mA Pin-Programmable LDO
Linear Regulators
_______________________________________________________________________________________ 7
DELAY
OUTPUT-
VOLTAGE
CONTROL
ERROR
AMP
MOS
DRIVER
WITH ILIMIT
87%
REF
1.50V
REF
THERMAL
SENSOR
UVLO/
SHUTDOWN
AND POWER-ON
CONTROL
LD02
IN OUT2
OUT1
RESET
(MAX8633 ONLY)
BP***
(MAX8634 ONLY)
GND
P1
P2
P
SHDN
SHDN1
SHDN2
IN
**
**
*
*MAX8633, MAX8636 ONLY
**MAX8634, MAX8635 ONLY
***MAX8634, MAX8636 ONLY
Functional Diagram
MAX8633–MAX8636
Detailed Description
The MAX8633–MAX8636 are low-power, low-quiescent
current, low-dropout linear regulators designed primari-
ly for battery-powered applications. Pin-programmable
inputs allow easy configuration of OUT1 and OUT2 volt-
ages without external 1% resistors. The devices can
supply up to 300mA from each output, provided they do
not exceed the maximum package power dissipation.
The MAX8633–MAX8636 regulate OUT1 and OUT2 by
using simple control loops incorporating internal 1.50V
reference, error amplifiers, p-channel pass transistors,
and internal feedback voltage-dividers. Reset circuitry
ensures controlled startup and provides undervoltage
lockout. The MAX8633–MAX8636 determine output
voltages at OUT1 and OUT2 based on the state of P1
and P2 (P for MAX8634) at power-on.
RESET
(MAX8633)
The MAX8633 features an integrated reset circuit.
RESET is logic-low on power-up and goes high imped-
ance 150ms after OUT2 reaches 87% of its nominal
regulation voltage. During power-down or undervoltage
conditions, RESET is driven low when OUT2 falls below
82.5% of its nominal regulation voltage.
Output Programming Inputs (P1, P2, P)
Output voltages for OUT1 and OUT2 are determined at
power-up by the state of P1 and P2. Programming
inputs P1 and P2 eliminate external 1% feedback resis-
tors while providing nine preset output-voltage options
(see Table 1 for the MAX8633; see Table 3 for the
MAX8635/MAX8636).
The MAX8634 provides three preset output-voltage
options with one programming input (see Table 2). The
MAX8633–MAX8636 configure output voltages at OUT1
and OUT2 based on the state of P1 and P2 (P for
MAX8634) at power-on. Subsequent changes to P, or
P1 and P2 do not change the output voltages unless
the supply power is cycled, or all SHDN inputs are
simultaneously driven low to shut down the device.
Power-On Sequence
(MAX8633/MAX8636 Only)
The MAX8633/MAX8636 provide a single shutdown input
(SHDN) to disable OUT1 and OUT2. During power-on,
inrush current is limited by a built-in startup sequence. At
power-on, OUT1 is disabled until OUT2 reaches 87% of
its regulation voltage, then OUT1 is enabled.
If SHDN is connected to IN and the input voltage drops
below the undervoltage-lockout (UVLO) threshold, both
LDOs are disabled. The LDOs will not power on again
until both of the following conditions are satisfied:
1) The input voltage is raised above the UVLO thresh-
old 2.25V (typ).
2) OUT2 is discharged below 1.2V (typ).
Internal p-Channel Pass Transistor
The MAX8633–MAX8636 feature 0.9Ωp-channel MOSFET
pass transistors; p-channel MOSFETs provide several
advantages over similar designs using pnp pass
transistors, resulting in higher efficiency and longer bat-
tery life. MOSFET pass transistors do not require base
drive current of pnps, reducing quiescent current
Dual 300mA Pin-Programmable LDO
Linear Regulators
8 _______________________________________________________________________________________
P1 P2 OUT1 (V) (OUT2) (V)
Open Open 2.80 1.50
Open GND 2.90 1.50
Open IN 3.00 1.50
GND Open 3.00 1.60
GND GND 2.80 1.80
GND IN 2.60 1.85
IN Open 2.90 1.85
IN GND 2.80 2.60
IN IN 3.00 2.80
Table 1. Output-Voltage Programming
(MAX8633)
P1 P2 OUT1 (V) OUT2 (V)
Open Open 2.80 1.50
Open GND 2.90 1.50
Open IN 3.00 1.50
GND Open 2.60 1.80
GND GND 2.80 1.80
GND IN 3.00 2.50
IN Open 3.00 2.80
IN GND 2.85 2.85
IN IN 3.00 3.00
Table 3. Output-Voltage Programming
(MAX8635/MAX8636)
P OUT1 (V) OUT2 (V)
Open 2.85 2.85
GND 3.00 2.85
IN 2.60 2.60
Table 2. Output-Voltage Programming
(MAX8634)
considerably. Under heavy loads, pnp base-drive cur-
rent becomes large, further reducing efficiency; pnp-
based regulators also require considerable current in
dropout when the pass transistor saturates. The
MAX8633–MAX8636 do not suffer from these problems.
With both outputs active, the devices consume only
54µA of quiescent current at no load, and 60µA with
100mA load current for each output (see
Typical
Operating Characteristics
). A pnp-based regulator has a
high dropout voltage that is independent of the load. The
dropout voltage of a p-channel MOSFET is proportional
to load current providing for low-dropout voltage at
heavy loads and extremely low dropout at lighter loads.
Current Limit
The MAX8633–MAX8636 provide independent current
limiting for OUT1 and OUT2. Output current is limited to
500mA (typ) and 400mA (min) for each regulator.
Shutdown (
SHDN1
,
SHDN2
,
SHDN
)
The MAX8634/MAX8635 have independent shutdown
control inputs (SHDN1 and SHDN2) and the MAX8633/
MAX8636 have one shutdown control input (SHDN) for
both outputs. Drive SHDN1 low to shut down OUT1.
Drive SHND2 low to shut down OUT2. Drive both SHDN1
and SHDN2 low to shut down the entire device, reducing
supply current to 1µA max. For the MAX8634, drive
SHDN low to shut down the entire device. Connect
SHDN1, SHDN2, or SHDN to a logic-high or IN to perma-
nently enable the corresponding LDO(s).
Thermal-Overload Protection
Thermal-shutdown circuitry protects the MAX8633–
MAX8636 from damage due to excessive junction tem-
perature. The shutdown circuit disables OUT1 and OUT2
when the junction temperature (TJ) exceeds +165°C.
Both regulators are reenabled when TJfalls by 15°C.
Low-Noise Operation (MAX8634/MAX8636)
An external 0.01µF bypass capacitor at BP in conjunc-
tion with an internal resistor creates a lowpass filter. The
MAX8634/MAX8636 exhibit less than 45µVRMS of out-
put voltage noise with CBP = 0.01µF and COUT = 2.2µF.
These values are shown in the Output Noise Spectral
Density graph in the
Typical Operating Characteristics
section. If output noise is not critical, omit the BP
capacitor to reduce total solution size and cost.
Applications Information
Capacitor Selection and
Regulator Stability
Use a ceramic input capacitor of at least 2.2µF and a
ceramic output capacitor of at least 2.2µF for each out-
put to ensure stable operation over the entire tempera-
ture range. Output capacitors can be reduced to 1µF
for load currents less than 150mA. The MAX8633–
MAX8636 are optimized for ceramic capacitors and
require low equivalent-series resistance (ESR) to
achieve the stated specifications for low-output noise
and power-supply rejection. To ensure proper opera-
tion over the specified temperature range, dielectrics
such as X7R or X5R are recommended. If Z5U or Y5V
dielectrics are used, it may be necessary to increase the
value of the output capacitors to ensure stability at tem-
peratures below -10°C. Tantalum capacitors are not re-
commended due to their higher ESR.
For loads up to 300mA, or for improved load-transient
response, 2.2µF or larger output capacitors can be used.
PSRR and Operation from
Sources Other than Batteries
The MAX8633–MAX8636 deliver low-dropout voltages
and low-quiescent currents in battery-powered systems.
When operating from sources other than batteries,
improved supply-noise rejection and transient response
can be achieved by increasing the values of the input
and output capacitors and through passive filtering tech-
niques. Power-supply rejection is 60dB at frequencies
below 1kHz (see the Power-Supply Rejection Ratio vs.
Frequency in the
Typical Operating Characteristics
).
P1 and P2 (P for MAX8634)
External Termination
The pin-programmable inputs (P1 and P2 for
MAX8633/MAX8635/MAX8636, P for MAX8634) should
be connected to IN, GND, or left open. If P_ inputs are
left open, ensure the external capacitance is less than
50pF. If P_ inputs are set high or low, ensure the resis-
tance to IN or GND is less than 1kΩ. The MAX8633–
MAX8636 configure output voltages at OUT1 and OUT2
based on the state of P1 and P2 (P for MAX8634) at
power-on. Subsequent changes to P, or P1 and P2 do
not change the output voltages unless the supply
power is cycled, or all SHDN inputs are simultaneously
driven low to shut down the device.
Load-Transient Considerations
The MAX8633–MAX8636 load-transient response
graphs (see
Typical Operating Characteristics
) show
two components of the output response: a DC step in
the output voltage due to the change in load current,
and the transient response. Increase the value and
decrease the ESR of the output capacitor to attenuate
transient spikes.
MAX8633–MAX8636
Dual 300mA Pin-Programmable LDO
Linear Regulators
_______________________________________________________________________________________ 9
MAX8633–MAX8636
Dual 300mA Pin-Programmable LDO
Linear Regulators
10 ______________________________________________________________________________________
Input-Output Voltage (Dropout Voltage)
A regulator’s minimum input-output voltage differential
(or dropout voltage) determines the lowest usable sup-
ply voltage. In battery-powered systems, this deter-
mines the useful end-of-life battery voltage. Because
the MAX8633–MAX8636 use a p-channel MOSFET
pass transistor, dropout voltage is a function of drain-
to-source on-resistance (RDS(ON)) multiplied by the
load current (see
Typical Operating Characteristics
).
Calculating Maximum Output Power
The maximum output power of the MAX8633–MAX8636
is limited by the maximum power dissipation of the
package. By calculating the power dissipation of the
device as a function of the input voltage, output volt-
ages, and output currents, the worst-case power dissi-
pation can be obtained. The worst-case power
dissipation should not exceed the package’s maximum
power rating:
where:
VIN(MAX) = Maximum input voltage
VOUT1 = Output voltage of OUT1
VOUT2 = Output voltage of OUT2
IOUT1 = Maximum output current of OUT1
IOUT2 = Maximum output current of OUT2
PDmust be less than PDMAX, the maximum power dis-
sipation of the package. If PDis greater than PDMAX,
consider using the 8-pin TDFN package.
PDMAX = 380mW for the 8-pin µDFN. Derate by
4.8mW/°C above +70°C.
PDMAX = 1904mW for the 8-pin TDFN. Derate by
23.8mW/°C above +70°C.
PC Board Layout Guidelines
Follow these guidelines for good PC board layout:
• Keep the input and output traces short and wide if
possible, especially at the ground terminals.
• Use thick copper PC boards to enhance thermal
performance. Connect the exposed paddle of the
TDFN package to the ground plane or a large cop-
per pad.
• Place output, input, and bypass capacitors as close
as possible to the IC.
• Ensure the noise bypass capacitor and associated
PC board traces are routed away from noise
sources to ensure low-output voltage noise.
An evaluation kit (MAX8633EVKIT) is available for a lay-
out example to speed designs.
PV V xI
VVxI
D IN MAX OUT OUT
IN MAX OUT OUT
=
()
+
−
()
()
()
–11
22
Ordering Information (continued)
PART TEMP RANGE PIN-
PACKAGE
TOP
MARK
MAX8634ETA+ -40°C to +85°C 8 TDFN
3mm x 3mm AOR
MAX8635ELA+ -40°C to +85°C 8 µDFN
2mm x 2mm AAJ
MAX8635ETA+ -40°C to +85°C 8 TDFN
3mm x 3mm AOS
MAX8636ELA+ -40°C to +85°C 8 µDFN
2mm x 2mm AAK
MAX8636ETA+ -40°C to +85°C 8 TDFN
3mm x 3mm AOT
PART
OUTPUT
VOLTAGE
OPTIONS
SHDN
INPUTS
LOW
NOISE RESET
MAX8633 9 1 — YES
MAX8634 3 2 YES —
MAX8635 9 2 — —
MAX8636 9 1 YES —
Selector Guide
+
Denotes a lead-free/RoHS-compliant package.
MAX8633–MAX8636
Dual 300mA Pin-Programmable LDO
Linear Regulators
______________________________________________________________________________________ 11
134
865
OUT1 GND RESET
MAX8633
2
7
OUT2
IN P2 P1SHDN
2mm x 2mm μDFN
3mm x 3mm TDFN
TOP VIEW
*EP
134
865
OUT1 GND BP
MAX8634
2
7
OUT2
IN SHDN2 PSHDN1
2mm x 2mm μDFN
3mm x 3mm TDFN
*EP
134
865
OUT1 GND SHDN2
MAX8635
2
7
OUT2
IN P2 P1SHDN1
2mm x 2mm μDFN
3mm x 3mm TDFN
*EP
134
865
OUT1 GND BP
MAX8636
2
7
OUT2
IN P2 P1SHDN
2mm x 2mm μDFN
3mm x 3mm TDFN
*EP
*EP = EXPOSED PADDLE. CONNECT EXPOSED PADDLE TO GND (TDFN ONLY).
Pin Configurations
Chip Information
PROCESS: BiCMOS
CONNECT EXPOSED PADDLE TO GND.
MAX8633–MAX8636
Dual 300mA Pin-Programmable LDO
Linear Regulators
12 ______________________________________________________________________________________
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
MAX8634
IN
SHDN2
OUT2
GND
OUT1
BP
SHDN1
P
COUT1
2.2μF
CIN
2.2μF
COUT2
2.2μF
CBP
0.01μF
CBP
0.01μF
INPUT
2.7V TO 5.5V
MAX8635
IN
SHDN2
OUT2
GND
OUT1
SHDN1
P2
P1
COUT1
2.2μF
CIN
2.2μF
COUT2
2.2μF
INPUT
2.7V TO 5.5V
MAX8636
IN
SHDN
OUT2
GND
OUT1
BP
P1
P2
COUT1
2.2μF
CIN
2.2μF
COUT2
2.2μF
INPUT
2.7V TO 5.5V
Typical Operating Circuits (continued)
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
8 TDFN T833-2 21-0137
8 µDFN L822-1 21-0164
MAX8633–MAX8636
Dual 300mA Pin-Programmable LDO
Linear Regulators
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________
13
© 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 4/06 Initial release —
1 9/08 Added LDO SHDN restart conditions 8