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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1809 Datasheet

3A / 1MHz / DDR Memory Termination Supply

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MAX1809 pdf
19-2142; Rev 1; 9/02
3A, 1MHz, DDR Memory Termination Supply
General Description
The MAX1809 is a reversible energy flow, constant-off-
time, pulse-width modulated (PWM), step-down DC-DC
converter. It is ideal for use in notebook and subnote-
book computers that require 1.1V to 5V active
termination power supplies. This device features an
internal PMOS power switch and internal synchronous
rectifier for high efficiency and reduced component
count. The internal 90mPMOS power switch and
70mNMOS synchronous-rectifier switch easily deliver
continuous load currents up to 3A. The MAX1809 accu-
rately tracks an external reference voltage, produces
an adjustable output from 1.1V to VIN, and achieves
efficiencies as high as 93%.
The MAX1809 uses a unique current-mode, constant-
off-time, PWM control scheme that allows the output to
source or sink current. This feature allows energy to
return to the input power supply that otherwise would
be wasted. The programmable constant-off-time archi-
tecture sets switching frequencies up to 1MHz, allowing
the user to optimize performance trade-offs between
efficiency, output switching noise, component size, and
cost. The MAX1809 features an adjustable soft-start to
limit surge currents during startup, a 100% duty-cycle
mode for low-dropout operation, and a low-power shut-
down mode that disables the power switches and
reduces supply current below 1µA. The MAX1809 is
available in a 28-pin QFN with an exposed backside
pad, a 28-pin thin QFN, or a 16-pin QSOP.
Applications
DDR Memory Termination
Active Termination Buses
Typical Operating Circuit
VIN
IN
LX
MAX1809 PGND
VCC GND
SHDN
VSET
EXTREF
FB
REF
TOFF SS
VOUT
Features
o Source/Sink 3A
o ±1% Output Accuracy
o Up to 1MHz Switching Frequency
o 93% Efficiency
o Internal PMOS/NMOS Switches
90m/70mOn-Resistance at VIN = 4.5V
110m/80mOn-Resistance at VIN = 3V
o 1.1V to VIN Adjustable Output Voltage
o 3V to 5.5V Input Voltage Range
o <1µA Shutdown Supply Current
o Programmable Constant-Off-Time Operation
o Thermal Shutdown
o Adjustable Soft-Start Inrush Current Limiting
o Output Short-Circuit Protection
Ordering Information
PART
TEMP RANGE
MAX1809EGI*
-40°C to +85°C
MAX1809EEE
-40°C to +85°C
MAX1809ETI
-40°C to +85°C
*Contact factory for availability.
PIN-PACKAGE
28 QFN
16 QSOP
28 Thin QFN
Pin Configurations
TOP VIEW
N.C. 1
IN 2
LX 3
IN 4
N.C. 5
SS 6
EXTREF 7
MAX1809
21 PGND
20 PGND
19 LX
18 LX
17 PGND
16 VCC
15 GND
THIN QFN
Pin Configurations continued at end of data sheet.
________________________________________________________________ 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

MAX1809 Datasheet

3A / 1MHz / DDR Memory Termination Supply

No Preview Available !

MAX1809 pdf
3A, 1MHz, DDR Memory Termination Supply
ABSOLUTE MAXIMUM RATINGS
VCC, IN to GND ........................................................-0.3V to +6V
IN to VCC.............................................................................±0.3V
GND to PGND.....................................................................±0.3V
SHDN, SS, FB, TOFF, RREF,
EXTREF to GND.......................................-0.3V to (VCC + 0.3V)
LX Current (Note 1).............................................................±4.7A
REF Short Circuit to GND Duration ............................Continuous
Continuous Power Dissipation (TA = +70°C)
28-Pin QFN (derate 20mW/°C above +70°C;
part mounted on 1in2 of 1oz copper) ..............................1.6W
16-Pin QSOP (derate 12.5mW/°C above +70°C;
part mounted on 1in2 of 1oz copper) .................................1W
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
Note 1: LX has clamp diodes to PGND and IN. If continuous current is applied through these diodes, thermal limits must be
observed.
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, VEXTREF = 1.1V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
Input Voltage
Feedback Voltage Accuracy
(VFB - VEXTREF)
Feedback Load Regulation Error
External Reference Voltage
Range
SYMBOL
CONDITIONS
VIN,VCC
VIN = VCC = 3V to 5.5V, ILOAD = 0,
VEXTREF = 1.25V (Note 2)
VFB ILOAD = -3A to +3A, VEXTREF = 1.25V
VEXTREF VIN = VCC = 3V to 5.5V
MIN
3.0
-12
VREF -
0.01
TYP
20
MAX
5.5
+12
VIN -
1.7
Reference Voltage
Reference Load Regulation
PMOS Switch
On-Resistance
NMOS Switch
On-Resistance
Current-Limit Threshold
Switching Frequency
No Load Supply Current
Shutdown Supply Current
Thermal-Shutdown Threshold
Undervoltage Lockout Threshold
FB Input Bias Current
Off-Time
Startup Off-Time
On-Time
VREF
RPMOS
RNMOS
ILIMIT
fSW
ICC
IIN
ISHDN
IFB
tOFF
IREF = -1µA to +10µA
ILX = 0.5A
VIN = 4.5V
VIN = 3V
ILX = 0.5A
VIN = 4.5V
VIN = 3V
VIN > VLX
(Note 3)
fSW = 500kHz
fSW = 500kHz
SHDN = GND, ICC + IIN
Hysteresis = 15°C
VCC falling, hysteresis = 90mV
VFB = VEXTREF + 0.1V
RTOFF = 30.1k
RTOFF = 110k
RTOFF = 499k
tON (Note 3)
1.078
3.5
2.5
0
0.24
0.9
3.8
0.35
1.100
0.5
90
110
70
80
4.1
1
16
<1
160
2.6
60
0.30
1.0
4.5
4 x tOFF
1.122
2.0
200
250
150
200
4.7
1
15
2.7
250
0.37
1.1
5.2
UNITS
V
mV
mV
V
V
mV
m
m
A
MHz
mA
µA
°C
V
nA
µs
µs
µs
2 _______________________________________________________________________________________


Part Number MAX1809
Description 3A / 1MHz / DDR Memory Termination Supply
Maker Maxim
Total Page 17 Pages
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