MAX1848EKA+T-MAX1848EKA-T-MAX1848ETA+T Fast Delivery |IC PHOENIX CO.,LIMITED

MAX1848EKA-T ,White LED Step-Up Converter in SOT23ELECTRICAL CHARACTERISTICS°° °°(V+ = 3V, V = 11V, L = 33µH, C = 1µF, C = 0.15µF, R = 5Ω, V = 1V, T ..
MAX1848EKA-T ,White LED Step-Up Converter in SOT23MAX184819-2028; Rev 2; 8/05White LED Step-Up Converter in SOT23
MAX1848ETA ,White LED Step-Up Converter in SOT23FeaturesThe MAX1848 drives white LEDs with a constant cur- Constant Current Regulation for Uniform ..
MAX1848ETA+T ,White LED Step-Up Converter in SOT23FeaturesThe MAX1848 drives white LEDs with a constant cur-♦ Constant Current Regulation for Uniform ..
MAX1848ETA+T ,White LED Step-Up Converter in SOT23ApplicationsPART TEMP RANGEPACKAGE MARKCell Phones and Smart PhonesMAX1848EKA-T -40°C to +85°C 8 SO ..
MAX184ACWG ,High-Speed 12-Bit A/D Converters With External Refernce inputFeatures . 12-Blt Resolutlon and Accuracy . Fast Conversion Tlmes: MAX183 - 3ps MAX184 - 5 ..
MAX475CPD ,Single/Dual/Quad, 10MHz Single-Supply Op AmpsFeaturesThe single MAX473, dual MAX474, and quad MAX475' 15V/µs Min Slew Rateare single-supply (2.7 ..
MAX475ESD ,Single/Dual/Quad, 10MHz Single-Supply Op AmpsELECTRICAL CHARACTERISTICS (continued)(+3V ≤ V ≤ +5V, V = 0V, V = 0.5V, V = 0.5V, T = +25°C, unless ..
MAX4760ETX+ ,High-Bandwidth, Quad DPDT SwitchesFeaturesThe MAX4760/MAX4760A/MAX4761/MAX4761A (DPDT)♦ USB 1.1 and USB 2.0 (Full Speed 12Mbps) analo ..
MAX4760EWX+T ,High-Bandwidth, Quad DPDT Switchesapplications.♦ Low-Capacitance Data SwitchesThe MAX4760/MAX4760A are quad double-pole/dou-ble-throw ..
MAX4761ETX+ ,High-Bandwidth, Quad DPDT SwitchesApplications ♦ Tiny 36-Bump UCSP (3mm x 3mm)♦ 36-Pin TQFN (6mm x 6mm)USB Signal Switching PDAs/Hand ..
MAX4761ETX+T ,High-Bandwidth, Quad DPDT SwitchesApplications ♦ Tiny 36-Bump UCSP (3mm x 3mm)♦ 36-Pin TQFN (6mm x 6mm)USB Signal Switching PDAs/Hand ..

MAX1848EKA+T-MAX1848EKA-T-MAX1848ETA+T
White LED Step-Up Converter in SOT23
General Description
The MAX1848 drives white LEDs with a constant cur-
rent to provide backlight in cell phones, PDAs, and
other hand-held devices. The step-up converter topology
allows series connection of the white LEDs so that the
LED currents are identical for uniform brightness. This
configuration eliminates the need for ballast resistors
and expensive factory calibration. Other benefits
include greater simplicity, lower cost, higher efficiency,
and greater reliability.
This step-up PWM converter includes an internal, high-
voltage, low RDSONN-channel MOSFET switch for high
efficiency and maximum battery life. A single analog
voltage Dual Mode™input provides a simple means of
brightness adjustment and on/off control. Fast 1.2MHz
current-mode PWM control allows for small input and
output capacitors and a small inductor while minimizing
ripple on the input supply/battery. Programmable soft-
start eliminates inrush current during startup.
The MAX1848 is available in space-saving 8-pin thin
QFN (3mm ✕3mm) and 8-pin SOT23 packages.
Applications
Cell Phones and Smart Phones
PDAs, Palmtops, and Wireless Handhelds
e-Books and Subnotebooks
White LED Display Backlighting
FeaturesConstant Current Regulation for Uniform
IlluminationHigh 87% EfficiencyAnalog or Logic Control of LED Intensity0.8W Output Power with Internal High-Voltage
MOSFET SwitchSmall, Low-Profile External Components2.6V to 5.5V Input Range13V Maximum Output with Overvoltage ProtectionOptimized for Low Input RippleProgrammable Soft-Start 0.3µA Shutdown CurrentSmall 8-pin Thin QFN (3mm ✕3mm) and
8-Pin SOT23 Packages
MAX1848
White LED Step-Up Converter in SOT23
GND
PGNDLXCTRL
OUT
COMP
SOT23
TOP VIEW
MAX1848
GND
PGNDLXCTRL
OUT
COMP
THIN QFN3mm x 3mm
MAX1848
Pin Configuration
Ordering Information
CTRL
COMP
OUT
PGND
GND
2.6V to 5.5V
LOGIC
OR DAC
CIN
3.3μF
CCOMP
0.15μF
33μH
COUT
1μF
RSENSE
MAX1848
Typical Application Circuit
19-2028; Rev 2; 8/05
PARTTEMP RANGEPIN-
PACKAGE
TOP
MARK
MAX1848EKA-T-40°C to +85°C8 SOT23AAIM
MAX1848ETA-T-40°C to +85°C8 Thin QFN
(3mm ✕ 3mm)ACR
MAX1848ETA+T-40°C to +85°C8 Thin QFN
(3mm ✕ 3mm)ACR
Note:Hand soldering is not recommended for the MAX1848
SOT23 package.
Dual Mode is a trademark of Maxim Integrated Products, Inc.
+ Denotes lead-free package.
MAX1848
White LED Step-Up Converter in SOT23
ABSOLUTE MAXIMUM RATINGS
DC ELECTRICAL CHARACTERISTICS
(V+ = 3V, VOUT= 11V, L = 33µH, COUT= 1µF, CCOMP= 0.15µF, RSENSE= 5Ω, VCTRL= 1V, TA= 0°°C to +85°°C, unless otherwise
noted. Typical values are at TA= +25°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.
V+ to GND................................................................-0.3V to +6V
PGND to GND.......................................................-0.3V to +0.3V
LX, OUT to GND.....................................................-0.3V to +14V
LX to OUT...............................................................-14V to +0.3V
CTRL to GND.......................................-0.3V to +6V or (V+ + 2V)
COMP, CS to GND.......................................-0.3V to (V+ + 0.3V)
LX Current....................................................................0.45ARMS
Continuous Power Dissipation (TA= +70°C)
8-Pin SOT23 (derate 9.7mW/°C above +70°C).............777mW
8-Pin Thin QFN 3mm ✕3mm (derate 24.4mW/°C
above +70°C)..............................................................1951mW
Operating Temperature Range...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-60°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
PARAMETERCONDITIONSMINTYPMAXUNITS
Supply Voltage2.65.5V
V+ rising, 40mV hysteresis typical2.152.382.59Undervoltage Lockout ThresholdV+ falling2.102.342.56V
Not switching, VCTRL = VCS = V+0.250.40Quiescent CurrentSwitching, VCTRL = V+, VCS = GND12mA
TA = +25°C0.31Shutdown Supply CurrentVCTRL = GNDTA = +85°C0.3µA
V+ rising, 1V hysteresis typical12.513.2514.0Overvoltage ThresholdV+ falling11.512.2513V
VCTRL > 0.25V102030OUT Input Bias CurrentVOUT = 13VVCTRL = GND0.011µA
Output Voltage RangeV+ -D IOD E 12.5V
ERROR AMPLIFIER
CTRL to CS RegulationVCTRL = 2V, V+ = 2.6V to 5.5V717581mV/V
CS Input Bias CurrentVCS = VCTRL /13.330.011µA
CTRL Input Resistance4506701100kΩ
CTRL Dual Mode ThresholdHysteresis = 25mV typical100170240mV
CS Line RegulationV+ = 2.6V to 5.5V, VCTRL = 3V0.05%/V
COMP Pin Resistance to GroundDevice in shutdown or overvoltage7.51550kΩ
COMP Output Voltage Swing0.32.4V
OSCILLATOR
Operating Frequency1.01.21.5MHz
PWM mode12Minimum Duty CyclePulse skipping0%
Maximum Duty CycleVCTRL = V+, VCS = GND859097%
MAX1848
White LED Step-Up Converter in SOT23
DC ELECTRICAL CHARACTERISTICS (continued)
(V+ = 3V, VOUT= 11V, L = 33µH, COUT= 1µF, CCOMP= 0.15µF, RSENSE= 5Ω, VCTRL= 1V, TA= 0°°C to +85°°C, unless otherwise
noted. Typical values are at TA= +25°C.)
DC ELECTRICAL CHARACTERISTICS
(V+ = 3V, VOUT= 11V, L = 33µH, COUT= 1µF, CCOMP= 0.15µF, RSENSE= 5Ω, VCTRL= 1V, TA= -40°°C to +85°°C, unless otherwise
noted. (Note 1)
PARAMETERCONDITIONSMINTYPMAXUNITS
N-CHANNEL SWITCH
LX On-ResistanceILX = 100mA1.42.2Ω
TA = +25°C0.012LX Leakage CurrentVOUT = VLX = 13VTA = +85°C0.05µA
LX Current LimitDuty cycle = 65%300500750mA
PARAMETERCONDITIONSMINMAXUNITS
Supply Voltage2.65.5V
V+ rising, 40mV hysteresis typical2.152.59Undervoltage Lockout ThresholdV+ falling2.102.56V
Not switching, VCTRL = VCS = V+0.4Quiescent CurrentSwitching, VCTRL = V+, VCS = GND2mA
V+ rising, 1V hysteresis typical12.2514.00Overvoltage ThresholdV+ falling11.2513.25V
VCTRL > 0.25V1030OUT Input Bias CurrentVOUT = 13VVCTRL = GND1µA
Output Voltage RangeV+ -
VDIODE12.25V
ERROR AMPLIFIER
CTRL to CS RegulationVCTRL = 2V, V+ = 2.6V to 5.5V6585mV/V
CS Input Bias CurrentVCS = VCTRL/13.331µA
CTRL Input Resistance4501100kΩ
CTRL Dual Mode ThresholdHysteresis = 25mV typical100240mV
COMP Pin Resistance to GroundDevice in shutdown or overvoltage7.550.0kΩ
COMP Output Voltage Swing0.32.4V
OSCILLATOR
Operating Frequency0.91.6MHz
Maximum Duty CycleVCTRL = V+, VCS = GND8597%
N-CHANNEL SWITCH
LX On-ResistanceILX = 100mA2.2Ω
LX Current LimitDuty cycle = 65%225850mA
Note 1:Limits are 100% production tested at TA= +25°C. Limits over the operating temperature range are guaranteed through cor-
relation using statistical quality control (SQC) methods.
MAX1848
White LED Step-Up Converter in SOT23
Typical Operating Characteristics
(See Typical Application Circuit, V+ = 3V, ILED= 15mA, L = 33µH, COUT= 1µF, CCOMP= 0.15µF, RSENSE= 5Ω, CTRL = 1V, 2 LEDs,= +25°C, unless otherwise noted.)
EFFICIENCY vs. SUPPLY VOLTAGE
MAX1848 toc01
SUPPLY VOLTAGE (V)
EFFICIENCY (%)
2 LEDs
3 LEDs
IOUT = 15mA
EFFICIENCY vs. LOAD CURRENT
MAX1848 toc02
LOAD CURRENT (mA)
EFFICIENCY (%)
2 LEDs
3 LEDs
SWITCHING FREQUENCY
vs. SUPPLY VOLTAGE
MAX1848 toc03
SUPPLY VOLTAGE (V)
SWITCHING FREQUENCY (MHz)
TA = +85°C
TA = +25°C
TA = -40°C
50ms/div
POWER-UP WAVEFORMS
VCTRL
IIN
ILED
38mA
MAX1848 toc04
15mA
tRISE = 15ms
CCOMP = 0.15μF
50ms/div
POWER-UP WAVEFORMS
VCTRL
IIN
ILED
38mA
MAX1848 toc05
15mA
tRISE = 110ms
CCOMP = 1μF
20μs/div
SHUTDOWN WAVEFORMS
VCTRL
IIN
ILED
38mA
MAX1848 toc06
15mA
2μs/div
SHUTDOWN WAVEFORMS
VCTRL
VOUT
VCOMP
6.3V
4.9V
MAX1848 toc07
1.5V
VOUT EVENTUALLY
DECAYS TO V+ = 3V
5ms/div
LINE-TRANSIENT RESPONSE
VIN
VOUT
ILED
3.00V
3.50V
6.25V500mV/div
MAX1848 toc08
15mA
10mA/div
CCOMP = 0.15μF
20ms/div
VCTRL TRANSIENT RESPONSE
VCTRL
VOUT
ILED
1.0V
2.0V
6.7V
6.3V
MAX1848 toc09
30mA
15mA
CCOMP = 0.15μF
MAX1848
White LED Step-Up Converter in SOT23
20ms/div
VCTRL TRANSIENT RESPONSE
VCTRL
VOUT
ILED
1.0V
2.0V
6.7V
6.3V
MAX1848 toc10
30mA
15mACCOMP = 1μF
Typical Operating Characteristics (continued)
(See Typical Application Circuit, V+ = 3V, ILED= 15mA, L = 33µH, COUT= 1µF, CCOMP= 0.15µF, RSENSE= 5Ω, CTRL = 1V, 2 LEDs,= +25°C, unless otherwise noted.)
200ns/div
SWITCHING WAVEFORMS
VLX
VIN_RIPPLE
6.5V
61mA
17mA
MAX1848 toc11
VOUT_RIPPLE
10mV/div
10mV/div
Pin Description
PINNAMEFUNCTIONCOMP
Compensation Pin for Error Amplifier. Connect capacitor from COMP to GND. Startup time is set
by the capacitance connected to this pin (0.833ms for each 0.01µF). VCOMP passively
discharges to GND when in shutdown.CTRL
Brightness/Shutdown Dual Mode Control Input. LED brightness and IC shutdown are controlled
by the voltage on CTRL. Voltages between 250mV and 5.5V or (V+ + 2V), whichever is less,
adjust the brightness from dim to bright, respectively. To put the IC into shutdown, drive below
100mV or connect to GND.OUT
Overvoltage Sense. When VOUT is greater than 13.25V, the internal N-channel MOSFET is turned
off and VCOMP decays to GND. When VOUT drops below 12.25V, the IC will re-enter soft-start.
Connect a 1µF capacitor from OUT to GND.LXInductor Connection. Drain of the internal high-voltage N-channel MOSFET.PGNDPower Ground. Source of the internal high-voltage N-channel MOSFET.GNDGround
7CSCurrent-Sense Feedback Input. Connect a resistor from this pin to GND to set the LED bias
current. This pin regulates to 7.5% of VCTRL.
8V+Supply Voltage Input. The IC is powered from this pin. Input range is 2.6V to 5.5V. Bypass with a
ceramic capacitor to GND.
MAX1848
Detailed Description
The MAX1848’s high efficiency and small size make it
ideally suited to drive series-connected LEDs. It oper-
ates as a boost DC-DC converter that controls output
current rather than voltage. The MAX1848 provides
even illumination by sending the same output current
through each LED, eliminating the need for expensive
factory calibration. The fast 1.2MHz internal oscillator
allows for a small inductor and small input and output
capacitors while minimizing input and output ripple.
The single analog control input allows easy adjustment
of LED brightness and on/off control. This allows either
simple logic-level on/off control or a DAC to control
both brightness and on/off. In shutdown, supply current
is reduced to a low 0.3µA. A programmable soft-start
gradually illuminates the LEDs, reducing the inrush cur-
rent during startup.
Soft-Start
The MAX1848 attains soft-start by charging CCOMP
gradually with a constant 12µA current. When VCOMP
rises above 1.25V, the internal MOSFET begins switch-
ing, but at a reduced duty cycle. When VCOMPrises
above 2.25V, the duty cycle will be at its maximum.
The maximum startup time is determined by the value
of CCOMP. For every 0.01µF connected to COMP, the
startup time will increase by 0.833ms. The start time
can be calculated by:
Shutdown
The MAX1848 is put into shutdown when VCTRLis less
than 100mV. In shutdown, supply current is reduced to
0.3µA by powering down the entire IC except for the
CTRL voltage detection circuitry. CCOMPis passively
discharged during shutdown, allowing the device to re-
initiate a soft-start whenever the device is enabled.
When in shutdown, the internal N-channel FET does not
switch, which leaves a current path between the input
and the LEDs through the boost inductor and Schottky
diode. The minimum forward voltage of the LED array
must exceed the maximum V+ to ensure that the LEDs
remain off in shutdown. Typical shutdown timing
characteristics are shown in the Typical Operating
Characteristics.
Overvoltage Protection
Overvoltage protection occurs when VOUTis above
13.25V. The protection circuitry stops the internal MOS-
FET from switching and causes VCOMPto decay to
GND. The device comes out of overvoltage lockout and
into soft-start when VOUTfalls below 12.25V.
Design Procedure
Adjusting LED Current
Adjusting the MAX1848’s output current will change the
brightness of the LEDs. An analog input (CTRL) and the
sense resistor value set the output current. Output cur-
rent is given by:
The VCTRLvoltage range for adjusting output current is
250mV to (V+ + 2V) or 5.5V, whichever is less. To set
the maximum current, calculate RSENSEwhen VCTRLis
at its maximum. Power dissipation in RSENSEis typically
less than 5mW; therefore, a standard chip resistor
is sufficient.
Capacitor Selection
The exact values of input and output capacitors are not
critical. The typical value for the input capacitor is
3.3µF, and the typical value for the output capacitor is
1.0µF. Larger value capacitors can be used to reduce
input and output ripple, but at the expense of size and
higher cost. V
13.33 RLEDCTRL
SENSE×VSOFTSTART (MAX)COMP-=×1
12μ
White LED Step-Up Converter in SOT23
PWM
CONTROL
CURRENT
SENSE
SLOPE
170mV
SHUTDOWN
50kΩ
617kΩ
PGND
OUT
COMP
CTRL
GND
1.2MHz
13.25V
MAX1848
Figure 1. Functional Diagram

Partno	Mfg	Dc	Qty	Available	Descript
MAX1848ETA+T	MAXIM ?	N/a	805	avai	White LED Step-Up Converter in SOT23
MAX1848ETA+T \|MAX1848ETAT	MAXIM	N/a	4212	avai	White LED Step-Up Converter in SOT23
MAX1848EKA+T \|MAX1848EKAT	MAX	N/a	9750	avai	White LED Step-Up Converter in SOT23
MAX1848EKA-T \|MAX1848EKAT	MAXIM	N/a	13460	avai	White LED Step-Up Converter in SOT23
MAX1848EKA-T \|MAX1848EKAT	MAX	N/a	235000	avai	White LED Step-Up Converter in SOT23