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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX1844 Datasheet

High-Speed Step-Down Controller

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MAX1844 pdf
19-1993; Rev 3; 9/02
EVAALVUAAILTAIOBNLEKIT High-Speed Step-Down Controller with
Accurate Current Limit for Notebook Computers
General Description
The MAX1844 pulse-width modulation (PWM) controller
provides high efficiency, excellent transient response,
and high DC output accuracy needed for stepping
down high-voltage batteries to generate low-voltage
CPU core or chipset/RAM supplies in notebook com-
puters.
www.DataSheeMt4aUx.cimom’s proprietary Quick-PWM™ quick-response,
constant-on-time PWM control scheme handles wide
input/output voltage ratios with ease and provides
100ns “instant-on” response to load transients while
maintaining a relatively constant switching frequency.
Efficiency is enhanced by an ability to drive very large
synchronous-rectifier MOSFETs. Accurate current sens-
ing to ensure reliable overload protection is available
using an external current-sense resistor in series with
the synchronous rectifier. Alternatively, the synchronous
rectifier itself can be used for less accurate current
sensing at the lowest possible power dissipation.
Single-stage buck conversion allows the MAX1844 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
battery) at a higher switching frequency allows the mini-
mum possible physical size.
The MAX1844 is intended for CPU core, chipset,
DRAM, or other low-voltage supplies as low as 1V. It is
available in 20-pin QSOP, and QFN packages and
includes both adjustable overvoltage and undervoltage
protection.
For a dual step-down PWM controller with accurate cur-
rent limit, refer to the MAX1845. The MAX1714/ MAX1715
single/dual PWM controllers are similar to the MAX1844/
MAX1845 but do not use current-sense resistors.
Notebook Computers
Applications
CPU Core Supplies
Chipset/RAM Supplies as Low as 1V
1.8V and 2.5V Supplies
*Contact factory for availability.
Quick-PWM is a trademark of Maxim Integrated Products.
Pin Configuration appears at end of data sheet.
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 1.8V/2.5V Fixed or 1V to 5.5V Adjustable Output
Range
o 2V to 28V Battery Input Range
o 200/300/450/600kHz Switching Frequency
o Adjustable Overvoltage Protection
o Adjustable Undervoltage Protection
o 1.7ms Digital Soft-Start
o Drives Large Synchronous-Rectifier FETs
o 2V ±1% Reference Output
o Power-Good Window Comparator
Ordering Information
PART
MAX1844EEP
MAX1844EGP*
MAX1844ETP
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
20 QSOP
20 QFN
20 Thin QFN
Minimal Operating Circuit
5V INPUT
BATTERY
4.5V TO 28V
VCC
SHDN
UVP
ILIM
VDD
V+
BST
DH
MAX1844
REF LX
DL
PGOOD CS
LATCH
OVP OUT
FB SKIP
GND
OUTPUT
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

MAX1844 Datasheet

High-Speed Step-Down Controller

No Preview Available !

MAX1844 pdf
High-Speed Step-Down Controller with
Accurate Current Limit for Notebook Computers
ABSOLUTE MAXIMUM RATINGS
V+ to GND ..............................................................-0.3V to +28V
VCC, VDD to GND .....................................................-0.3V to +6V
OUT, PGOOD, SHDN to GND ..................................-0.3V to +6V
FB, ILIM, LATCH, OVP, REF, SKIP,
TON, UVP to GND ..................................-0.3V to (VCC + 0.3V)
BST to GND ............................................................-0.3V to +34V
CS to GND.................................................................-6V to +30V
www.DataSheeDDtLH4Uttoo.cGoLmXND.......................................................................................................--00..33VV
to
to
(VDD
(BST
+
+
0.3V)
0.3V)
LX to BST..................................................................-6V to +0.3V
REF Short Circuit to GND ...........................................Continuous
Continuous Power Dissipation (TA = +70°C)
20-Pin QSOP (derate 9.1mW/°C above +70°C)...........727mW
20-Pin 5mm 5mm QFN (derate 20.0mW/°C
above +70°C).................................................................1.60W
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
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, V+ = 15V, VCC = VDD = 5V, SKIP = GND, TA = 0°C to +85°C, unless otherwise noted. Typical values are at
TA = +25°C.)
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Input Voltage Range
Battery voltage, V+
VCC , VDD
2 28
V
4.5 5.5
Error Comparator Threshold
(DC Output Voltage Accuracy)
(Note 1)
Load Regulation Error
V+ = 4.5V to 28V,
SKIP = VCC
ILOAD = 0 to 3A, SKIP = VCC
FB = OUT
FB = GND
FB = VCC
0.99
2.475
1.782
1.01
2.5 2.525 V
1.8 1.818
9 mV
Line Regulation Error
FB Input Bias Current
VCC = 4.5V to 5.5V, V+ = 4.5V to 28V
5 mV
-0.1
+0.1
µA
Output Adjustment Range
1 5.5 V
OUT Input Resistance
Soft-Start Ramp Time
FB = GND
FB = VCC or adjustable feedback mode
Rising edge of SHDN to full current limit
90 190 350
k
70 145 270
1.7 ms
On-Time
V+ = 24V,
VOUT = 2V
(Note 2)
TON = GND (600kHz)
TON = REF (450kHz)
TON = unconnected (300kHz)
TON = VCC (200kHz)
140 160 180
175 200 225
ns
260 290 320
380 425 470
Minimum Off-Time
(Note 2)
400 500 ns
Quiescent Supply Current (VCC)
Quiescent Supply Current (VDD)
FB forced above the regulation point
FB forced above the regulation point
550 800 µA
<1 5 µA
Quiescent Supply Current (V+)
25 40 µA
Shutdown Supply Current (VCC)
Shutdown Supply Current (VDD)
Shutdown Supply Current (V+)
SHDN = GND
SHDN = GND
SHDN = GND, V+ = 28V, VCC = VDD = 0 or 5V
<1 5 µA
<1 5 µA
<1 5 µA
Reference Voltage
Reference Load Regulation
VCC = 4.5V to 5.5V, no external REF load
IREF = 0 to 50µA
1.98
2.00
2.02
0.01
V
V
2 _______________________________________________________________________________________


Part Number MAX1844
Description High-Speed Step-Down Controller
Maker Maxim Integrated Products
Total Page 24 Pages
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