MAX1549ETL Datasheet, PDF (1/35 Pages) Maxim Integrated Products – Dual, Interleaved, Fixed-Frequency Step-Down Controller with a Dynamically Adjustable Output

19-3165; Rev 0; 1/04
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Dual, Interleaved, Fixed-Frequency Step-Down
Controller with a Dynamically Adjustable Output
General Description
The MAX1549 dual pulse-width modulation (PWM) step-
down controller provides the high efficiency, excellent
transient response, and high DC-output accuracy nec-
essary for generating low-voltage chipset and RAM
power supplies in notebook computers. The controller
employs a fixed-frequency, current-mode PWM archi-
tecture that does not require complex compensation.
The MAX1549 also interleaves the dual step-down regu-
lators, minimizing the input capacitor requirements.
The MAX1549 features differential current-sense inputs
for accurately sensing the inductor current across an
external current-sense resistor in series with the output
to ensure reliable overload protection. Alternatively, the
controller can provide overload protection using loss-
less inductor current-sensing methods, lowering power
dissipation and reducing system cost.
Single-stage buck conversion allows the MAX1549 to
directly step down high-voltage batteries for the highest
possible efficiency. Very low output-voltage applica-
tions require two-stage conversion—stepping down
from another system supply rail instead of the battery.
The MAX1549 powers chipsets and graphics processor
cores that require dynamically adjustable output voltages,
or generates the active termination bus that must track
the input reference. The main step-down controller
(OUT1) regulates the dedicated reference input (REFIN)
voltage generated by a resistive voltage-divider from the
MAX1549’s reference. The MAX1549 also includes inter-
nal open-drain pulldowns with logic-level control inputs to
dynamically adjust the REFIN resistive-divider ratio. When
a transition occurs on these control inputs, the controller
enters forced-PWM mode and blanks the power-good
(PGOOD1) output and output fault protection. OUT2 uses
a Dual-Mode™ feedback input to provide either fixed
2.5V/1.8V or adjustable output voltage regulation. The
MAX1549 is available in a 40-pin, 6mm x 6mm thin QFN
package.
Applications
Notebook Computers
Dynamically Adjustable Chipset Supplies
Video/GPU Core Supplies
DDR Memory Termination
CPU Core or V_CC Supplies
Fixed Chipset/RAM Supplies
Active Termination Buses
Features
♦ Interleaved, Fixed-Frequency, Current-Mode
Control Architecture
♦ 1% V_OUT Accuracy Over Line and Load
♦ Main Output (OUT1)
0.5V to 2.0V Adjustable Output
External Reference Input for Dynamically
Selectable Output Voltages
Four Digitally Selectable Output Voltages
Power-Good and Fault Blanking During
Transitions
♦ Second Output (OUT2)
2.5V/1.8V Fixed or 0.5V to 2.7V Adjustable
Output
♦ Accurate Differential Current-Sense Inputs
♦ 100kHz/200kHz/300kHz/400kHz Selectable
Switching Frequency
♦ Output Overvoltage/Undervoltage Protection
♦ Soft-Start and Soft-Shutdown
♦ Drives Large Synchronous-Rectifier FETs
♦ 2V ±0.6% Reference Output
♦ Separate Enable Inputs with Accurate Threshold
Voltages
♦ Separate Power-Good Window Comparators
Ordering Information
PART
MAX1549ETL
TEMP RANGE PIN-PACKAGE
-40°C to +85°C 40 Thin QFN 6mm x 6mm
Pin Configuration
TOP VIEW
40 39 38 37 36 35 34 33 32 31
GND 1
N.C. 2
REF 3
VCC 4
CC1 5
ILIM1 6
ILIM2 7
G0 8
G1 9
FBLANK 10
MAX1549
30 LX1
29 BST1
28 SKIP
27 DL1
26 VDD
25 N.C.
24 DL2
23 PGND
22 BST2
21 LX2
11 12 13 14 15 16 17 18 19 20
Dual Mode is a trademark of Maxim Integrated Products, Inc.
THIN QFN
6mm x 6mm
________________________________________________________________ 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.