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PDF MAX15046 Data sheet ( Hoja de datos )
| Número de pieza | MAX15046 | |
| Descripción | 40V High-Performance Synchronous Buck Controller | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-4719; Rev 0; 7/09
www.DataSheet4U.com
40V, High-Performance, Synchronous
Buck Controller
General Description
The MAX15046 synchronous step-down controller oper-
ates from a 4.5V to 40V input voltage range and gener-
ates an adjustable output voltage from 85% of the input
voltage down to 0.6V, supporting loads up to 25A. The
device allows monotonic startup into a prebiased bus
without discharging the output and features adaptive
internal digital soft-start.
The MAX15046 offers the ability to adjust the switching
frequency from 100kHz to 1MHz with an external resis-
tor. The MAX15046’s adaptive synchronous rectifica-
tion eliminates the need for an external freewheeling
Schottky diode. The device also utilizes the external
low-side MOSFET’s on-resistance as a current-sense
element, eliminating the need for a current-sense resis-
tor. This protects the DC-DC components from damage
during output overloaded conditions or output short-
circuit faults without requiring a current-sense resistor.
Hiccup-mode current limit reduces power dissipation
during short-circuit conditions. The MAX15046 includes
a power-good output and an enable input with precise
turn-on/turn-off threshold, which can be used for input
supply monitoring and for power sequencing.
Additional protection features include sink-mode current
limit, and thermal shutdown. Sink-mode current limit pre-
vents reverse inductor current from reaching dangerous
levels when the device is sinking current from the output.
The MAX15046 is available in a 16-pin QSOP or 16-pin
QSOP-EP package and operates over the -40NC to +125NC
temperature range.
Pin Configurations appear at end of data sheet.
Features
S Input Voltage Ranges from 4.5V to 40V or 5V
Q10%
S Adjustable Outputs from 0.85 x VIN Down to 0.6V
S Adjustable Switching Frequency (100kHz to 1MHz)
with Q10% (1MHz) Accuracy
S Adaptive Internal Digital Soft-Start
S Up to 25A Output Capability
S Cycle-by-Cycle Valley-Mode Current Limit with
Adjustable, Temperature-Compensated Threshold
(30mV to 300mV)
S Monotonic Startup into Prebiased Output
S Q1% Accurate Voltage Reference
S 3A-Peak Gate Drivers
S Hiccup-Mode Short-Circuit Protection (Patent-
Pending Architecture)
S Overtemperature Shutdown
S Power-Good (PGOOD) Output and Enable Input
(EN) with Q5% Accurate Threshold
S Thermally Enhanced 16-Pin QSOP Package
Applications
Industrial Power Supplies (PLC, Industrial
Computers, Fieldbus Components, Fieldbus
Couplers)
Telecom Power Supplies
Base Stations
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX15046AAEE+ -40°C to +125°C 16 QSOP
MAX15046BAEE+ -40°C to +125°C 16 QSOP-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Typical Operating Circuit
4.5V TO 40V
VIN
ON
OFF
R4
C1
C5 R3
C6
C7
R1 R3
IN
VCC MAX15046
PGOOD
CSP
DH
LX
EN BST
LIM DL
COMP
DRV
FB PGND
RT GND
R2
C2
D1
C4
R5
Q1
L1
Q2
0.6V TO 0.85V x VIN
VOUT
C3
________________________________________________________________ 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.
1 page  
www.DataSheet4U.com
40V, High-Performance Synchronous
Buck Controller
(VIN = 24V, TA = +25NC, unless otherwise noted.)
Typical Operating Characteristics
100
90
80
70
60
50
40
30
20
10
0
0
EFFICIENCY vs. LOAD CURRENT
(VIN = 24V)
VOUT = 3.3V VOUT = 1.8V
VOUT = 5V
VOUT = 1.2V
3 6 9 12
LOAD CURRENT (A)
15
VCC vs. LOAD CURRENT
5.256
5.254
5.252
5.250
5.248
5.246
5.244
5.242
0
5 10 15 20 25 30 35 40 45
LOAD CURRENT (mA)
1000
900
800
700
600
500
400
300
200
100
0
0
SWITCHING FREQUENCY
vs. RRT
40 80 120
RRT (kI)
160
100
90
80
70
60
50
40
30
20
10
0
0
EFFICIENCY vs. LOAD CURRENT
(VIN = 12V)
VOUT = 1.8V
VOUT = 1.2V
VOUT = 3.3V VOUT = 5V
3 6 9 12
LOAD CURRENT (A)
15
VCC LINE REGULATION
5.2
5.0 IVCC = 5mA, 10mA, 20mA, 30mA
4.8
4.6
4.4
IVCC = 40mA
4.2
4.0
0
5 10 15 20 25 30 35 40
VIN (V)
SWITCHING FREQUENCY
vs. TEMPERATURE
1200
1000
800
RT = 14.3kI
RT = 25.5kI
600
400 RT = 49.9kI
200 RT = 150kI
0
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (NC)
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
0
VOUT vs. LOAD CURRENT
2 4 6 8 10 12
LOAD CURRENT (A)
VCC vs. TEMPERATURE
5.266
ILOAD = 5mA
5.265
5.264
5.263
5.262
5.261
5.260
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (NC)
IIN vs.
SWITCHING FREQUENCY
2.8
CDH = CDL = 0
2.7
2.6
2.5
2.4
2.3
2.2
100
FREQUENCY (kHz)
1000
_______________________________________________________________________________________ 5
5 Page 
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40V, High-Performance, Synchronous
Buck Controller
to function properly. The stray impedance in the gate
discharge path can cause the sense circuitry to interpret
the MOSFET gate as “off” while the VGS of the MOSFET
is still high. To minimize stray impedance, use very short,
wide traces.
Synchronous rectification reduces conduction losses in
the rectifier by replacing the normal low-side Schottky
catch diode with a low-resistance MOSFET switch. The
MAX15046 features a robust internal pulldown transistor
with a typical 1I RDS(ON) to drive DL low. This low on-
resistance prevents DL from being pulled up during the
fast rise time of the LX node, due to capacitive coupling
from the drain to the gate of the low-side synchronous
rectifier MOSFET.
High-Side Gate-Drive Supply (BST)
An external Schottky diode between BST and DH is
required to boost the gate voltage above LX providing
the necessary gate-to-source voltage to turn on the high-
side MOSFET. The boost capacitor connected between
BST and LX holds up the voltage across the floating gate
driver during the high-side MOSFET on-time.
The charge lost in the boost capacitor for delivering the
gate charge is replenished when the high-side MOSFET
turns off and the LX node goes to ground. When LX is
low, the external diode between VDRV and BST recharg-
es the boost capacitor. See the Boost Capacitor and
Diode Selection section in the Applications Information
to choose the right boost capacitor and diode.
Enable Input (EN), Soft-Start, and Soft-Stop
Drive EN high to turn on the MAX15046. A soft-start
sequence starts to increase (step-wise) the reference
voltage of the error amplifier. The duration of the soft-
start ramp is 2048 switching cycles and the resolution is
1/64th of the steady-state regulation voltage allowing a
smooth increase of the output voltage. A logic-low on EN
initiates a soft-stop sequence by stepping down the ref-
erence voltage of the error amplifier. After the soft-stop
sequence is completed, the MOSFET drivers are both
turned off. See Figure 1.
Connect EN to VCC for always-on operation. Owing to
the accurate turn-on/-off thresholds, EN can be used
as a UVLO adjustment input, and for power sequencing
together with the PGOOD outputs.
UVLO
VCC
A
EN
VOUT
DAC_VREF
DH
DL
BC
D
E F GH
2048 CLOCK
CYCLES
2048 CLOCK
CYCLES
I
SYMBOL
UVLO
VCC
EN
VOUT
DAC_VREF
DH
DL
A
DEFINITION
Undervoltage threshold value is provided in
the Electrical Characteristics table.
Internal 5.25V linear regulator output.
Active-high enable input.
Regulator output voltage.
Regulator internal soft-start and soft-stop signal.
Regulator high-side gate-driver output.
Regulator low-side gate-driver output.
VCC rising while below the UVLO threshold.
EN is low.
Figure 1. Power On-Off Sequencing
SYMBOL
B
C
D
E
F
G
H
I
DEFINITION
VCC is higher than the UVLO threshold. EN is low.
EN is pulled high. DH and DL start switching.
Normal operation.
VCC drops below UVLO.
VCC goes above the UVLO threshold. DH and DL
start switching. Normal operation.
EN is pulled low. VOUT enters soft-stop.
EN is pulled high. DH and DL start switching.
Normal operation.
VCC drops below UVLO.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 23 Páginas | |
| PDF Descargar | [ Datasheet MAX15046.PDF ] | |
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