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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1845 Datasheet

Dual / High-Efficiency / Step-Down Controller with Accurate Current Limit

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MAX1845 pdf
19-1955; Rev 2; 1/03
EVAALVUAAILTAIOBNLEKIT
Dual, High-Efficiency, Step-Down
Controller with Accurate Current Limit
General Description
The MAX1845 is a dual PWM controller configured for
step-down (buck) topologies that provides high efficien-
cy, excellent transient response, and high DC output
accuracy necessary for stepping down high-voltage bat-
teries to generate low-voltage chipset and RAM power
supplies in notebook computers. The CS_ inputs can be
used with low-side sense resistors to provide accurate
current limits or can be connected to LX_, using low-side
MOSFETs as current-sense elements.
The on-demand PWM controllers are free running, con-
stant on-time with input feed-forward. This configuration
provides ultra-fast transient response, wide input-output
differential range, low supply current, and tight load-reg-
ulation characteristics. The MAX1845 is simple and easy
to compensate.
Single-stage buck conversion allows the MAX1845 to
directly step down high-voltage batteries for the highest
possible efficiency. Alternatively, two-stage conversion
(stepping down the 5V system supply instead of the bat-
tery at a higher switching frequency) allows the minimum
possible physical size.
The MAX1845 is intended for generating chipset, DRAM,
CPU I/O, or other low-voltage supplies down to 1V. For a
single-output version, refer to the MAX1844 data sheet.
The MAX1845 is available in 28-pin QSOP and 36-pin
thin QFN packages.
Features
o Ultra-High Efficiency
o Accurate Current-Limit Option
o Quick-PWM™ with 100ns Load-Step Response
o 1% VOUT Accuracy over Line and Load
o Dual Mode™ Fixed 1.8V/1.5V/Adj or 2.5V/Adj Outputs
o Adjustable 1V to 5.5V Output Range
o 2V to 28V Battery Input Range
o 200/300/420/540kHz Nominal Switching Frequency
o Adjustable Overvoltage Protection
o 1.7ms Digital Soft-Start
o Drives Large Synchronous-Rectifier FETs
o Power-Good Window Comparator
o 2V ±1% Reference Output
PART
MAX1845EEI
MAX1845ETX
Ordering Information
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 QSOP
36 Thin QFN
6mm 6mm
Applications
Notebook Computers
CPU Core Supplies
Chipset/RAM Supply as Low as 1V
1.8V and 2.5V I/O Supplies
5V INPUT
OUTPUT1
1.8V
Pin Configurations appear at end of data sheet.
Quick-PWM and Dual Mode are trademarks of Maxim Integrated
Products.
Minimal Operating Circuit
VDD
VCC
ILIM1
ILIM2
ON1
ON2
BST1
V+
UVP
OVP
BST2
DH1 DH2
LX1 LX2
DL1 DL2
TON
CS1
OUT1
PGOOD
REF
CS2
OUT2
SKIP
FB1 FB2
GND
BATTERY
4.5V TO 28V
MAX1845EEI
OUTPUT2
2.5V
________________________________________________________________ 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

MAX1845 Datasheet

Dual / High-Efficiency / Step-Down Controller with Accurate Current Limit

No Preview Available !

MAX1845 pdf
Dual, High-Efficiency, Step-Down
Controller with Accurate Current Limit
ABSOLUTE MAXIMUM RATINGS (Note 1)
V+ to AGND..............................................................-0.3 to +30V
VCC to AGND............................................................-0.3V to +6V
VDD to PGND............................................................-0.3V to +6V
AGND to PGND .....................................................-0.3V to +0.3V
PGOOD, OUT_ to AGND..........................................-0.3V to +6V
OVP, UVP, ILIM_, FB_, REF,
SKIP, TON, ON_ to AGND......................-0.3V to (VCC + 0.3V)
DL_ to PGND ..............................................-0.3V to (VDD + 0.3V)
BST_ to AGND........................................................-0.3V to +36V
CS_ to AGND.............................................................-6V to +30V
DH1 to LX1 ..............................................-0.3V to (VBST1 + 0.3V)
LX_ to BST_ ..............................................................-6V to +0.3V
DH2 to LX2 ..............................................-0.3V to (VBST2 + 0.3V)
REF Short Circuit to GND ...........................................Continuous
Continuous Power Dissipation (TA = +70°C)
28-Pin QSOP (derate 10.8mW/°C above +70°C)........860mW
36-Pin 6mm 6mm Thin QFN
(derate 26.3mW/°C above +70°C) .............................2105mW
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: For the MAX1845EEI, AGND and PGND refer to a single pin designated GND.
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
(Circuit of Figure 1, VDD = VCC = 5V, SKIP = AGND, V+ = 15V, TA = 0°C to +85°C, typical values are at +25°C, unless otherwise
noted.)
PARAMETER
PWM CONTROLLERS
Input Voltage Range
DC Output Voltage OUT1
(Note 2)
DC Output Voltage OUT2
(Note 2)
SYMBOL
CONDITIONS
V+ Battery voltage, V+
VCC/VDD VCC, VDD
VOUT1
V+ = 2V to 28V, ILOAD
= 0 to 8A, SKIP = VCC,
+25°C to +85°C
V+ = 2V to 28V, ILOAD
= 0 to 8A, SKIP = VCC,
0°C to +85°C
VOUT2
V+ = 4.5V to 28V,
ILOAD = 0 to 4A,
SKIP = VCC,
+25°C to +85°C
V+ = 4.5V to 28V,
ILOAD = 0 to 4A,
SKIP = VCC,
0°C to +85°C
FB1 to AGND
FB1 to VCC
FB1 to OUT1
FB1 to AGND
FB1 to VCC
FB1 to OUT1
FB2 to AGND
FB2 to OUT2
FB2 to AGND
FB2 to OUT2
MIN TYP MAX UNITS
2 28
4.5 5.5
1.782 1.8 1.818
1.485 1.5 1.515
0.99 1 1.01
1.773 1.8 1.827
1.477 1.5 1.523
0.985 1 1.015
2.475 2.5 2.525
0.99 1 1.01
2.463 2.5 2.537
0.985 1 1.015
V
V
V
Output Voltage Adjust Range
Dual-Mode Threshold, Low
OUT1, OUT2
OVP, FB_
1 5.5
0.05 0.1 0.15
V
V
Dual-Mode Threshold, High
OUT_ Input Resistance
FB_ Input Bias Current
Soft-Start Ramp Time
OVP, ILIM_
ROUT1
ROUT2
IFB
FB1
VOUT1 = 1.5V
VOUT2 = 2.5V
Zero to full ILIM
VCC -
1.5
1.9
75
100
-0.1
VCC -
0.4
2.0 2.1
1700
0.1
V
k
µA
µs
2 _______________________________________________________________________________________


Part Number MAX1845
Description Dual / High-Efficiency / Step-Down Controller with Accurate Current Limit
Maker Maxim
Total Page 27 Pages
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