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PDF MAX15026 Data sheet ( Hoja de datos )
| Número de pieza | MAX15026 | |
| Descripción | DC-DC Synchronous Buck Controller | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX15026 (archivo pdf) en la parte inferior de esta página. Total 22 Páginas | ||
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19-4108; Rev 0; 5/08
EVAALVUAAILTAIOBNLEKIT
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
www.datasheet4u.com
General Description
The MAX15026 synchronous step-down controller oper-
ates from a 4.5V to 28V input voltage range and gener-
ates an adjustable output voltage from 85% of the input
voltage down to 0.6V while supporting loads up to 25A.
The device allows monotonic startup into a prebiased
bus without discharging the output and features adap-
tive internal digital soft-start.
The MAX15026 offers the ability to adjust the switching
frequency from 200kHz to 2MHz with an external resis-
tor. The MAX15026’s adaptive synchronous rectification
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 MAX15026 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 cur-
rent limit and thermal shutdown.
Sink-mode current limit prevents reverse inductor cur-
rent from reaching dangerous levels when the device is
sinking current from the output.
The MAX15026 is available in a space-saving and ther-
mally enhanced 3mm x 3mm, 14-pin TDFN-EP pack-
age. The MAX15026 operates over the -40°C to +85°C
temperature range.
Applications
Set-Top Boxes
LCD TV Secondary Supplies
Switches/Routers
Power Modules
DSP Power Supplies
Points-of-Load Regulators
Features
♦ 4.5V to 28V or 5V ±10% Input Supply Range
♦ 0.6V to (0.85 x VIN) Adjustable Output
♦ Adjustable 200kHz to 2MHz Switching Frequency
♦ Ability to Start into a Prebiased Load
♦ Lossless, Cycle-by-Cycle Valley Mode Current
Limit with Adjustable, Temperature-Compensated
Threshold
♦ Sink-Mode Current-Limit Protection
♦ Adaptive Internal Digital Soft-Start
♦ ±1% Accurate Voltage Reference
♦ Internal Boost Diode
♦ Adaptive Synchronous Rectification Eliminates
External Freewheeling Schottky Diode
♦ Hiccup-Mode Short-Circuit Protection
♦ Thermal Shutdown
♦ Power-Good Output and Enable Input for Power
Sequencing
♦ ±5% Accurate Enable Input Threshold
Ordering Information
PART
TEMP RANGE
MAX15026BETD+ -40°C to +85°C
+Denotes a lead-free package.
*EP = Exposed pad.
PIN-PACKAGE
14 TDFN-EP*
Pin Configuration
TOP VIEW
IN 1
VCC 2
PGOOD 3
EN 4
LIM 5
COMP 6
FB 7
+
MAX15026
*EP
14 DH
13 LX
12 BST
11 DL
10 DRV
9 GND
8 RT
*EP = EXPOSED PAD.
TDFN
(3mm x 3mm)
________________________________________________________________ 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  
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
www.datasheet4u.com
Typical Operating Characteristics
(VCC = VIN = 12V, TA = +25°C, unless otherwise noted.) (See the circuit of Figure 5.)
100
90
80
70
60
50
40
30
20
10
0
0
EFFICIENCY vs. LOAD CURRENT
VOUT = 3.3V
VOUT = 1.2V
VOUT = 5V
VOUT = 1.8V
2 4 6 8 10 12
LOAD CURRENT (A)
100
90
80
70
60
50
40
30
20
10
0
0
EFFICIENCY vs. LOAD CURRENT
(VIN = 12V, VCC = VDRV = 5V)
VOUT = 5V
VOUT = 3.3V
VOUT = 1.8V
VOUT = 1.2V
2 4 6 8 10 12
LOAD CURRENT (A)
0
-0.1
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
-0.8
-0.9
-1.0
0
VOUT vs. LOAD CURRENT
24
6 8 10 12
LOAD CURRENT (A)
5.265
5.260
5.255
5.250
5.245
5.240
5.235
5.230
5.225
0
2500
VCC vs. LOAD CURRENT
20 40 60 80
LOAD CURRENT (mA)
SWITCHING FREQUENCY
vs. RESISTANCE
100
2000
1500
1000
500
0
0 20 40 60 80 100
RESISTANCE (kΩ)
5.3
5mA
5.2
VCC LINE REGULATION
5.1
5.0 50mA
4.9
4.8
4.7
4.6
4.5
4.4
4.3
0
5 10 15 20 25
VIN (V)
30
SWITCHING FREQUENCY
vs. TEMPERATURE
2500
2000
RRT = 7.2kΩ
1500 RRT = 15.7kΩ
RRT = 27kΩ
RRT = 85kΩ
1000
500
0
-40
-15 10 35 60
TEMPERATURE (°C)
85
VCC vs. TEMPERATURE
5.248
5.246
5.244
5.242
5.240
5.238
5.236
-40
-15 10 35 60
TEMPERATURE (°C)
85
90
80
70
60
50
40
30
20
10
0
100
SUPPLY CURRENT
vs. SWITCHING FREQUENCY
1000
SWITCHING FREQUENCY (kHz)
10,000
_______________________________________________________________________________________ 5
5 Page 
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
www.datasheet4u.com
UVLO
A
BC
D
E
F GH
I
VCC
EN
VOUT
DAC_VREF
2048 CLK
CYCLES
2048 CLK
CYCLES
DH
DL
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
Current-Limit Circuit (LIM)
The current-limit circuit employs a valley and sink cur-
rent-sensing algorithm that uses the on-resistance of
the low-side MOSFET as a current-sensing element, to
eliminate costly sense resistors. The current-limit circuit
is also temperature compensated to track the on-resis-
tance variation of the MOSFET over temperature. The
current limit is adjustable with an external resistor at
LIM, and accommodates MOSFETs with a wide range
of on-resistance characteristics (see the Setting the
Valley Current Limit section). The adjustment range is
from 30mV to 300mV for the valley current limit, corre-
sponding to resistor values of 6kΩ to 60kΩ. The valley
current-limit threshold across the low-side MOSFET is
precisely 1/10th of the voltage at LIM, while the sink
current-limit threshold is 1/20th of the voltage at LIM.
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.
Valley current limit acts when the inductor current flows
towards the load, and LX is more negative than GND
during the low-side MOSFET on-time. If the magnitude
of current-sense signal exceeds the valley current-limit
threshold at the end of the low-side MOSFET on-time,
the MAX15026 does not initiate a new PWM cycle and
lets the inductor current decay in the next cycle. The
controller also rolls back the internal reference voltage
so that the controller finds a regulation point deter-
mined by the current-limit value and the resistance of
the short. In this manner, the controller acts as a con-
stant current source. This method greatly reduces
inductor ripple current during the short event, which
reduces inductor sizing restrictions, and reduces the
possibility for audible noise. After a timeout, the device
goes into hiccup mode. Once the short is removed, the
internal reference voltage soft-starts back up to the nor-
mal reference voltage and regulation continues.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet MAX15026.PDF ] | |
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