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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX8643A Datasheet

2MHz Step-Down Regulator

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19-0767; Rev 2; 10/09
3A, 2MHz Step-Down Regulator
with Integrated Switches
General Description
The MAX8643A high-efficiency switching regulator
delivers up to 3A load current at output voltages from
0.6V to (0.9 x VIN). The IC operates from 2.35V to 3.6V,
making it ideal for on-board point-of-load and postregu-
lation applications. Total output error is less than ±1%
over load, line, and temperature.
The MAX8643A features fixed-frequency PWM mode
operation with a switching frequency range of 500kHz
to 2MHz set by an external resistor. High-frequency
operation allows for an all-ceramic capacitor design.
The high operating frequency also allows for small-size
external components.
The low-resistance on-chip nMOS switches ensure high
efficiency at heavy loads while minimizing critical induc-
tances, making the layout a much simpler task with
respect to discrete solutions. Following a simple layout
and footprint ensures first-pass success in new designs.
The MAX8643A comes with a high-bandwidth (> 14MHz)
voltage-error amplifier. The voltage-mode control archi-
tecture and the voltage-error amplifier permit a type III
compensation scheme to be utilized to achieve maxi-
mum loop bandwidth, up to 20% of the switching fre-
quency. High loop bandwidth provides fast transient
response, resulting in less required output capacitance
and allowing for all-ceramic capacitor designs.
The MAX8643A provides two three-state logic inputs to
select one of nine preset output voltages. The preset
output voltages allow customers to achieve ±1% out-
put-voltage accuracy without using expensive 0.1%
resistors. In addition, the output voltage can be set to
any customer value by either using two external resis-
tors at the feedback with 0.6V internal reference or
applying an external reference voltage to the REFIN
input. The MAX8643A offers programmable soft-start
time using one capacitor to reduce input inrush current.
The MAX8643A is available in a lead-free, 24-pin, 4mm
x 4mm thin QFN package.
Applications
POLs
ASIC/CPU/DSP Core and I/O Voltages
DDR Power Supplies
Base-Station Power Supplies
Telecom and Networking Power Supplies
RAID Control Power Supplies
Pin Configuration appears at end of data sheet.
Features
o Internal 37mRDSON MOSFETs
o Continuous 3A Output Current
o ±1% Output Accuracy Over Load, Line,
and Temperature
o Operates from 2.35V to 3.6V Supply
o Adjustable Output from 0.6V to (0.9 x VIN)
o Soft-Start Reduces Inrush Supply Current
o 500kHz to 2MHz Adjustable Switching Frequency
o Compatible with Ceramic, Polymer, and
Electrolytic Output Capacitors
o VID-Selectable Output Voltages
0.6, 0.7, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0, and 2.5V
o Fully Protected Against Overcurrent
and Overtemperature
o Safe-Start into Prebiased Output
o Sink/Source Current in DDR Applications
o Lead-Free, 24-Pin, 4mm x 4mm Thin QFN Package
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX8643AETG+
-40°C to +85°C 24 Thin QFN-EP*
MAX8643AETG/V+ -40°C to +85°C 24 Thin QFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive qualified part.
*EP = Exposed pad.
INPUT
2.4V TO 3.6V
Typical Operating Circuit
IN BST
MAX8643A
EN
LX
VDD
OUT
OUTPUT
1.8V, 3A
CTL1
CTL2
FREQ
REFIN
SS
PGND
FB
COMP
VDD
PREBIAS
PWRGD
GND
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.


Maxim Integrated Semiconductor Electronic Components Datasheet

MAX8643A Datasheet

2MHz Step-Down Regulator

No Preview Available !

3A, 2MHz Step-Down Regulator
with Integrated Switches
ABSOLUTE MAXIMUM RATINGS
IN, VDD, PWRGD to GND ......................................-0.3V to +4.5V
COMP, FB, REFIN, OUT,
CTL_, EN, SS, FREQ to GND...................-0.3V to (VDD + 0.3V)
LX Current (Note 1) .....................................................-4A to +4A
BST to LX..................................................................-0.3V to +4V
PGND to GND .......................................................-0.3V to +0.3V
Continuous Power Dissipation (TA = +70°C)
24-Pin TQFN-EP
(derated 27.8mW/°C above +70°C)........................2222.2mW
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 internal clamp diodes to GND and IN. Applications that forward bias these diodes should take care not to exceed
the IC’s 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 = VDD = 3.3V, VFB = 0.5V, TA = -40°C to +85°C. Typical values are at TA = +25°C, circuit of Figure 1, unless otherwise noted.) (Note 2)
PARAMETER
IN/VDD
IN and VDD Voltage Range
IN Supply Current
VDD Supply Current
Total Shutdown Current from IN
and VDD
VDD Undervoltage Lockout
Threshold
BST
BST Supply Current
PWM COMPARATOR
PWM Comparator Propagation
Delay
COMP
COMP Clamp Voltage, High
COMP Slew Rate
PWM Ramp Amplitude
COMP Shutdown Resistance
ERROR AMPLIFIER
CONDITIONS
fS = 1MHz, no load
(includes gate-drive current)
fS = 1MHz
VIN = 2.5V
VIN = 3.3V
VIN = 2.5V
VIN = 3.3V
VIN = VDD = VBST - VLX = 3.6V, VEN = 0V
LX starts/stops switching
VDD rising
VDD falling
Deglitching
VBST = VDD = VIN = 3.6V,
VLX = 3.6V or 0V, VEN = 0V
TA = +25°C
TA = +85°C
10mV overdrive
VIN = 2.35V to 3.6V
From COMP to GND, VEN = VSS = 0V
Preset Output-Voltage Accuracy REFIN = SS
FB Regulation Accuracy Using
External Resistors
FB to OUT Resistor
CTL1 = CTL2 = GND
All VID settings except CTL1 = CTL2 = GND
MIN TYP MAX UNITS
2.35 3.60 V
4 4.6
5.5
mA
1.4 2.3
2
mA
13 µA
2 2.1
1.8 1.9
2
V
µs
5
µA
10
20 ns
2V
1.4 V/µs
1V
8
Select
-1 from +1
Table 1
0.594 0.600 0.606
5 8 11
%
V
k
2 _______________________________________________________________________________________


Part Number MAX8643A
Description 2MHz Step-Down Regulator
Maker Maxim Integrated Products
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MAX8643A Datasheet PDF






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