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PDF MAX1549 Data sheet ( Hoja de datos )
| Número de pieza | MAX1549 | |
| Descripción | Fixed-Frequency Step-Down Controller | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX1549 (archivo pdf) en la parte inferior de esta página. Total 30 Páginas | ||
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19-3165; Rev 0; 1/04
EVAALVUAAILTAIOBNLEKIT
www.DataSheet4U.com
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 VCC Supplies
Fixed Chipset/RAM Supplies
Active Termination Buses
Features
♦ Interleaved, Fixed-Frequency, Current-Mode
Control Architecture
♦ 1% VOUT 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
N.C.
REF
VCC
CC1
ILIM1
ILIM2
G0
G1
FBLANK
1
2
3
4
5
6
7
8
9
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.
1 page  
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Dual, Interleaved, Fixed-Frequency Step-Down
Controller with a Dynamically Adjustable Output
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VCC = VDD = 5V, SKIP = GND, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
Logic Input Current
Dual-Mode Threshold Voltage
Four-Level Input Logic Levels
Four-Level Logic Input Current
SYMBOL
CONDITIONS
ON_, SKIP, G0, G1
FB2
High
Low
High
FSEL, FBLANK
Open
REF
Low
FSEL, FBLANK forced to GND or VCC
MIN TYP MAX UNITS
-1 +1 µA
1.9 2.0 2.1
0.05 0.1 0.15
V
VCC -
0.4V
3.15 3.85 V
1.65 2.35
0.5
-3 +3 µA
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VCC = VDD = 5V, SKIP = GND, TA = -40°C to +85°C, unless otherwise noted.) (Note 4)
PARAMETER
INPUT SUPPLIES (Note 1)
Input Voltage Range
Quiescent Supply Current (VCC)
SYMBOL
CONDITIONS
VBIAS
ICC
VCC, VDD
OUT1 and FB2 forced above their
regulation points
MIN
4.5
Quiescent Supply Current (VDD)
Shutdown Supply Current (VCC)
Shutdown Supply Current (VDD)
PWM CONTROLLERS
IDD
OUT1 and FB2 forced above their
regulation points
ON1 = ON2 = GND, SKIP = VCC
ON1 = ON2 = GND
Main Output-Voltage Accuracy
(OUT1 Tracking)
VREFIN -
VOUT1
With respect to
50% duty cycle
REFIN, SKIP = VCC
or GND
10% to 90% duty cycle
Secondary Preset Output-Voltage
Accuracy (OUT2 Fixed)
Secondary Feedback-Voltage
Accuracy (FB2 Adjustable)
Output Adjust Range
OUT2 Input Resistance
VOUT2
VFB2
ROUT2
SKIP = VCC, 50% FB2 = GND
duty cycle (Note 1) FB2 = VCC
SKIP = VCC
(Note 1)
50% duty cycle
10% to 90% duty cycle
OUT1 (tracks REFIN)
OUT2
FB2 = GND or adjustable
FB2 = VCC
OUT_ Discharge-Mode
On-Resistance
RDISCHARGE
-8
-10
2.470
1.775
0.490
0.485
0.5
0.5
120
85
OUT_ Synchronous-Rectifier
Discharge-Mode Turn-On Level
0.2
MAX UNITS
5.5 V
1.8 mA
5 µA
5 µA
5 µA
+8
+10
2.530
1.825
0.510
0.515
2.0
2.7
460
335
40
mV
V
V
V
kΩ
Ω
0.4 V
_______________________________________________________________________________________ 5
5 Page 
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Dual, Interleaved, Fixed-Frequency Step-Down
Controller with a Dynamically Adjustable Output
PIN
1
2, 20,
25, 31
3
4
5
6
7
8, 9
10
11
12
13
14
NAME
GND
FUNCTION
Analog Ground. Connect backside pad to GND.
Pin Description
N.C. Not Internally Connected
REF
VCC
CC1
ILIM1
ILIM2
G0, G1
FBLANK
FSEL
2.0V Reference Voltage Output. Bypass to analog ground with a 0.1µF or greater ceramic capacitor. The
reference can source up to 100µA for external loads. Loading REF degrades output voltage accuracy
according to the REF load-regulation error. The reference shuts down when both MAX1549 outputs are
disabled.
Analog Supply Input. Connect to the system supply voltage (+4.5V to +5.5V) through a series 20Ω
resistor. Bypass VCC to analog ground with a 1µF or greater ceramic capacitor.
Integrator Capacitor Connection. Connect a 47pF to 1000pF (470pF typ) capacitor from CC1 to analog
ground (GND) to set the integration time constant for the main MAX1549 controller (OUT1).
Current-Limit Threshold Adjustment for Controller 1. The current-limit threshold defaults to 70mV if ILIM1
is connected to VCC. In adjustable mode, the current-limit threshold across CSH1 and CSL1 is precisely
1/10th the voltage seen at ILIM1 over a 0.5V to 2.0V range. The logic threshold for switchover to the
70mV default value is approximately VCC - 1V.
Current-Limit Threshold Adjustment for Controller 2. The current-limit threshold defaults to 70mV if ILIM2
is connected to VCC. In adjustable mode, the current-limit threshold across CSH2 and CSL2 is precisely
1/10th the voltage seen at ILIM2 over a 0.5V to 2.0V range. The logic threshold for switchover to the
70mV default value is approximately VCC - 1V.
Buffered N-Channel MOSFET Gate Inputs. See Table 4.
Fault-Blanking Select Input. This four-level logic input enables or disables fault blanking and sets the
minimum forced-PWM operation time (tFBLANK). When fault blanking is enabled, the MAX1549 blanks
the PGOOD1 output and main (OUT1) controller’s OVP/UVP fault protection for the selected time period
after the controller detects a transition on G0 or G1. Additionally, the main controller enters forced-PWM
mode for the duration of tFBLANK anytime G0 or G1 changes states.
OUT1 fault protection and PGOOD1 blanking:
VCC = 150µs, open = 100µs, REF = 50µs, GND = blanking disabled
Automatic forced-PWM transition operation (OUT1 only):
VCC = 150µs, open = 100µs, REF = 50µs, GND = 100µs
Frequency-Select Input. This four-level logic input sets the controller’s switching frequency. Connect to
GND, REF, VCC, or leave FSEL unconnected (open) to select the following typical switching frequencies:
VCC = 400kHz, open = 300kHz, REF = 200kHz, GND = 100kHz
ON1
OUT1 Enable Input. Pull to GND to shut down controller 1 (OUT1). Connect to VCC for normal operation.
The output is discharged through a 12Ω resistor between OUT1 and GND, and DL1 is forced high after
VOUT1 drops below 0.3V. A rising edge on ON1 or ON2 clears the fault-protection latch.
ON2
CSH2
OUT2 Enable Input. Pull to GND to shut down controller 2 (OUT2). Connect to VCC for normal operation.
The output is discharged through a 12Ω resistor between OUT2 and GND, and DL2 is forced high after
VOUT2 drops below 0.3V. A rising edge on ON1 or ON2 clears the fault-protection latch.
Positive Current-Sense Input for Controller 2. Connect to the positive terminal of the current-sense
element. Figure 8 describes current-sensing options. The PWM controller does not begin a cycle unless
the current sensed is less than the current-limit threshold programmed at ILIM2.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet MAX1549.PDF ] | |
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