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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1843 Datasheet

2.7A / 1MHz / Low-Voltage / Step-Down Regulator with Internal Synchronous Rectification in QFN Package

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MAX1843 pdf
19-1986; Rev 1; 3/02
EVALUATION KIT
AVAILABLE
2.7A, 1MHz, Low-Voltage, Step-Down Regulator with
Internal Synchronous Rectification in QFN Package
General Description
The MAX1843 constant-off-time, pulse-width modulated
(PWM) step-down DC-DC converter is ideal for use in 5V
and 3.3V to low-voltage conversion necessary in note-
book and subnotebook computers. This device features
an internal PMOS power switch and internal synchronous
rectification for high efficiency and reduced component
count. An external Schottky diode is not required. The
internal 90mpower switch and 70mNMOS synchro-
nous-rectifier switch easily deliver continuous load cur-
rents up to 2.7A. The MAX1843 produces a preset +2.5V,
+1.8V, or +1.5V output voltage or an adjustable output
from +1.1V to VIN. It achieves efficiencies as high as
95%.
The MAX1843 uses a unique current-mode, constant-off-
time, PWM control scheme, which includes Idle Mode™
to maintain high efficiency during light-load operation.
The programmable constant-off-time architecture sets
switching frequencies up to 1MHz, allowing the user to
optimize performance trade-offs between efficiency, out-
put switching noise, component size, and cost. The
MAX1843 features an adjustable soft-start to limit surge
currents during startup, a 100% duty-cycle mode for low
dropout operation, and a low-power shutdown mode that
disconnects the input from the output and reduces sup-
ply current below 1µA. The MAX1843 is available in a 28-
pin QFN package with an exposed backside pad.
Applications
5V or 3.3V to Low-Voltage Conversion
CPU I/O Ring
Chipset Supplies
Notebook and Subnotebook Computers
Typical Configuration
INPUT
+3V TO
+5.5V
10
2.2µF
470pF
IN LX
MAX1843 FB
VCC
SHDN
COMP
TOFF
PGND
GND
FBSEL
REF
SS
OUTPUT
+1.1V TO
VIN
0.01µF
1µF
Idle Mode is a trademark of Maxim Integrated Products.
Features
o ±1% Output Accuracy
o Up to 1MHz Switching Frequency
o 95% Efficiency
o Internal PMOS/NMOS Switches
90m/70mOn-Resistance at VIN = +4.5V
110m/80mOn-Resistance at VIN = +3V
o Output Voltage
+2.5V, +1.8V, or +1.5V Pin Selectable
+1.1V to VIN Adjustable
o +3V to +5.5V Input Voltage Range
o 350µA Operating Supply Current
o <1µA Shutdown Supply Current
o Programmable Constant-Off-Time Operation
o Idle Mode Operation at Light Loads
o Thermal Shutdown
o Adjustable Soft-Start Inrush Current Limiting
o 100% Duty Cycle During Low-Dropout Operation
o Output Short-Circuit Protection
o 28-Pin QFN Package
PART
MAX1843EGI
Ordering Information
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
28 QFN
Pin Configuration
TOP VIEW
28 27
N.C. 1
26 25
24 23
22
21 PGND
IN 2
20 PGND
LX 3
19 LX
IN 4
N.C. 5
MAX1843
18 LX
17 PGND
SS 6
16 VCC
COMP 7
15 FBSEL
8 9 10 11 12 13 14
QFN
________________________________________________________________ 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.


Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1843 Datasheet

2.7A / 1MHz / Low-Voltage / Step-Down Regulator with Internal Synchronous Rectification in QFN Package

No Preview Available !

MAX1843 pdf
2.7A, 1MHz, Low-Voltage, Step-Down Regulator with
Internal Synchronous Rectification in QFN Package
ABSOLUTE MAXIMUM RATINGS
VCC, IN to GND ........................................................-0.3V to +6V
IN to VCC.............................................................................±0.3V
GND to PGND.....................................................................±0.3V
All Other Pins to GND.................................-0.3V to (VCC + 0.3V)
LX Current (Note 1).............................................................±4.7A
REF Short Circuit to GND Duration ............................Continuous
ESD Protection .....................................................................±2kV
Continuous Power Dissipation (TA = +70°C)
28-Pin QFN (derate 20mW/°C above +70°C, part mounted
on 1in2 of 1oz copper)......................................................1.6W
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature ......................................................+150°C
Lead Temperature (soldering, 10s) ................................ +300°C
Note 1: LX has internal clamp diodes to PGND and IN. Applications that forward bias these diodes should take care not to exceed the
ICs package power dissipation limits.
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 = VCC = +3.3V, FBSEL = GND, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
Input Voltage
Preset Output Voltage
SYMBOL
VIN, VCC
VIN =
+3V to
+5.5V
VOUT
ILOAD =
0 to 2.5A
CONDITIONS
FBSEL = VCC
FBSEL =
unconnected
FBSEL = REF
TA = +25°C
to +85°C
TA = 0°C to
+85°C
TA = +25°C
to +85°C
TA = 0°C to
+85°C
TA = +25°C
to +85°C
TA = 0°C to
+85°C
MIN TYP MAX UNITS
3.0 5.5 V
2.500 2.525 2.550
2.487 2.525 2.563
1.500 1.515 1.530
1.492 1.515 1.538
1.800 1.818 1.836
V
1.791 1.818 1.845
VFB =
VOUT
FBSEL = GND
TA = +25°C
to +85°C
TA = 0°C to
+85°C
1.089 1.100 1.111
1.084 1.100 1.117
Adjustable Output Voltage
Range
VIN = VCC = +3V to +5.5V, FBSEL = GND
VREF
VIN V
AC Load Regulation Error
DC Load Regulation Error
Dropout Voltage
Reference Voltage
Reference Load Regulation
PMOS Switch On-Resistance
NMOS Switch On-Resistance
Current-Limit Threshold
RMS LX Output Current
VDO
VREF
VREF
RON,P
RON,N
ILIMIT
VIN = VCC = +3V, ILOAD = 1A
TA = +25°C to +85°C
TA = 0°C to +85°C
IREF = -1µA to +10µA
ILX = 0.5A
VIN = +4.5V
VIN = +3V
ILX = 0.5A
VIN = +4.5V
VIN = +3V
1.089
1.084
3.1
2
0.4
1.100
1.100
0.5
90
110
70
80
3.6
250
1.111
1.117
2
200
250
150
200
4.1
3.1
%
%
mV
V
mV
m
m
A
A
2 _______________________________________________________________________________________


Part Number MAX1843
Description 2.7A / 1MHz / Low-Voltage / Step-Down Regulator with Internal Synchronous Rectification in QFN Package
Maker Maxim
Total Page 13 Pages
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