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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX8855A Datasheet

2MHz Step-Down Regulators

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19-0726; Rev 4; 10/11
EVAALVUAAILTAIOBNLEKIT Dual, 5A, 2MHz Step-Down Regulators
General Description
The MAX8855/MAX8855A high-efficiency, dual step-down
regulators are capable of delivering up to 5A at each out-
put. The devices operate from a 2.25V to 3.6V supply, and
provide output voltages from 0.6V to 0.9 x VIN, making them
ideal for on-board point-of-load applications. Total output
error is less than ±1% over load, line, and temperature.
The MAX8855/MAX8855A operate in PWM mode with a
switching frequency ranging from 0.5MHz to 2MHz, set
by an external resistor. It can also be synchronized to
an external clock in the same frequency range. Two
internal switching regulators operate 180° out-of-phase
to reduce the input ripple current, and consequently
reduce the required input capacitance. The high
operating frequency minimizes the size of external
components. High efficiency, internal dual-nMOS
design keeps the board cool under heavy loads. The
voltage-mode control architecture and the high-band-
width (> 15MHz typ) voltage-error amplifier allow a type
III compensation scheme to be utilized to achieve fast
response under both line and load transients, and also
allow for ceramic output capacitors.
Programmable soft-start reduces input inrush current.
Two enable inputs allow the turning on/off of each out-
put individually, resulting in great flexibility for system-
level designs. A reference input is provided to facilitate
output-voltage tracking applications. The MAX8855/
MAX8855A are available in a 32-pin TQFN (5mm x 5mm)
package with 0.8mm max height.
Applications
ASIC/CPU/DSP Power Supplies
DDR Power Supplies
Set-Top Box Power Supplies
Printer Power Supplies
Network Power Supplies
Features
o 27mΩ On-Resistance Internal MOSFETs
o Dual, 5A, PWM Step-Down Regulators
o Fully Protected Against Overcurrent,
Short Circuit, and Overtemperature
o ±1% Output Accuracy Over Load, Line,
and Temperature
o Operates from 2.25V to 3.6V Supply
o REFIN on One Channel for Tracking or
External Reference
o Integrated Boost Diodes
o Adjustable Output from 0.6V to 0.9 x VIN
o Soft-Start Reduces Inrush Supply Current
o 0.5MHz to 2MHz Adjustable Switching,
or FSYNC Input
o All-Ceramic-Capacitor Design
o 180° Out-of-Phase Operation Reduces Input
Ripple Current
o Individual Enable Inputs and PWRGD Outputs
o Safe-Start into Prebiased Output
o Available in 5mm x 5mm Thin QFN Package
o Sink/Source Current in DDR Applications
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX8855ETJ+
-40°C to +85°C 32 TQFN-EP*
MAX8855AETJ+
-40°C to +85°C 32 TQFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Typical Operating Circuit
OUTPUT1
1.2V / 5A
INPUT1
2.25V TO 3.6V
IN1 IN2
BST1 BST2
LX1 LX2
INPUT2
2.25V TO 3.6V
OUTPUT2
1.5V / 5A
PGND1 PGND2
MAX8855/
MAX8855A
FB1 FB2
Pin Configuration appears at end of data sheet.
TYPE III
COMPENSATION
ON
OFF
COMP1 COMP2
PWRGD1 PWRGD2
EN1 EN2
GND
TYPE III
COMPENSATION
ON
OFF
________________________________________________________________ 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.
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Maxim Integrated Semiconductor Electronic Components Datasheet

MAX8855A Datasheet

2MHz Step-Down Regulators

No Preview Available !

Dual, 5A, 2MHz Step-Down Regulators
ABSOLUTE MAXIMUM RATINGS
IN_, LX_, VDD, VDL, PWRGD_ to GND..................-0.3V to +4.5V
VDD, VDL to IN_.....................................................-0.3V to +4.5V
EN_, SS_, COMP_, FB_, REFIN, FSYNC to GND ......-0.3V to the
lower of (VVDD + 0.3V) and (VVDL + 0.3V)
Continuous LX_ Current (Note 1) ...................................5.5ARMS
BST_ to LX_ ...........................................................-0.3V to +4.5V
PGND_ to GND......................................................-0.3V to +0.3V
Continuous Power Dissipation (TA = +70°C)
32-Pin TQFN (5mm x 5mm)
(derate 34.5mW/°C above +70°C) ..........................2758.6mW
Operating Ambient Temperature Range .............-40°C to +85°C
Operating Junction Temperature Range ...........-40°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
Note 1: LX_ have internal clamp diodes to PGND_ 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.
PACKAGE THERMAL CHARACTERISTICS (Note 2)
TQFN
Junction-to-Ambient Thermal Resistance (θJA) ...........29°C/W
Junction-to-Case Thermal Resistance (θJC) ...............1.7°C/W
Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
ELECTRICAL CHARACTERISTICS
(VIN_ = VVDD = VVDL = 3.3V, VFB_ = 0.5V, VSS_ = VREFIN = 600mV, PGND_ = GND, RFSYNC = 10kΩ, L = 0.47μH, CBST_ = 0.1μF,
CSS_ = 0.022μF, PWRGD_ not connected; TA = -40°C to +85°C, typical values are at TA = +25°C, unless otherwise noted.) (Note 2)
PARAMETER
IN1, IN2, VDL, VDD
IN_, VDL, and VDD Voltage Range
IN_ Supply Current
VDD + VDL Supply Current
Shutdown Supply Current
(IIN1 + IIN2 + IVDD + IVDL)
IN_, VDD Undervoltage Lockout Threshold
UVLO Monitors VDD, IN1, and IN2
IN_, VDD Undervoltage Lockout Deglitch
BST1, BST2
Shutdown BST_ Current
COMP1, COMP2
COMP_ Clamp Voltage, High
COMP_ Slew Rate
COMP_ Shutdown Resistance
CONDITIONS
MIN
(Note 3)
MAX8855
MAX8855A
1MHz switching, no load
1MHz switching, VDD = VDL
VIN_ = VVDD = VVDL = VBST_ -
VLX_ = 3.6V, VEN_ = 0V
Rising
VIN_ = 2.5V
VIN_ = 3.3V
VVDD = 2.5V
VVDD = 3.3V
TA = +25°C
TA = +85°C
Falling
2.35
2.25
1.8
VIN_ = VVDD = VVDL = VBST_ = TA = +25°C
3.6V, VEN_ = 0V, VLX_ = 0 or 3.6V TA = +85°C
VVDD = VIN_ = 2.25V to 3.6V, VFB_ = 0.7V
From COMP_ to GND, VEN_ = 0V
1.80
TYP MAX UNITS
3.60
V
3.60
1.9 3.5
mA
2.8 5
7.2
mA
10 15
11
0.3
μA
2.0 2.2
1.9
V
2 μs
2
0.02
μA
2.00 2.25
V
1.40 V/μs
7 25 Ω
2 _______________________________________________________________________________________
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Part Number MAX8855A
Description 2MHz Step-Down Regulators
Maker Maxim
Total Page 20 Pages
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