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PDF MAX5089 Data sheet ( Hoja de datos )
| Número de pieza | MAX5089 | |
| Descripción | 2.2MHz - 2A Buck Converters with an Integrated High-Side Switch | |
| Fabricantes | Maxim Integrated Products | |
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19-3944; Rev 1; 5/06
EVAALVUAAILTAIOBNLEKIT
www.DataSheet4U.com
2.2MHz, 2A Buck Converters with an
Integrated High-Side Switch
General Description
The MAX5088/MAX5089 high-frequency, DC-DC con-
verters with an integrated n-channel power MOSFET
provide up to 2A of load current. The MAX5088
includes an internal power MOSFET to enable the
design of a nonsynchronous buck topology power sup-
ply. The MAX5089 is for the design of a synchronous
buck topology power supply. These devices operate
from a 4.5V to 5.5V or 5.5V to 23V input voltage and a
200kHz to 2.2MHz resistor-programmable switching
frequency. The voltage-mode architecture with a peak
switch current-limit scheme provides stable operation
up to a 2.2MHz switching frequency. The MAX5088
includes a clock output for driving a second DC-DC
converter 180° out-of-phase and a power-on-reset
(RESET) output. The MAX5089 includes a power-good
output and a synchronous rectifier driver to drive an
external low-side MOSFET in the buck converter config-
uration for high efficiency.
The MAX5088/MAX5089 protect against overcurrent
conditions by utilizing a peak current limit as well as
overtemperature shutdown providing a very reliable
and compact power source for point-of-load regulation
applications. Additional features include synchroniza-
tion, internal digital soft-start, and an enable input. The
MAX5088/MAX5089 are available in a thermally
enhanced, space-saving 16-pin TQFN (5mm x 5mm)
package and operate over the -40°C to +125°C tem-
perature range.
Applications
xDSL Modem Power Supply
Automotive Radio Power Supply
Servers and Networks
IP Phones/WLAN Access Points
Features
♦ 4.5V to 5.5V or 5.5V to 23V Input Voltage Range
♦ Output Voltage Adjustable Down to 0.6V
♦ 2A Output Current
♦ Synchronous Rectifier Driver Output (MAX5089)
for Higher Efficiency
♦ Resistor-Programmable Switching Frequency
from 200kHz to 2.2MHz
♦ External Synchronization and Enable (On/Off)
Inputs
♦ Clock Output for Driving Second Converter 180°
Out-Of-Phase (MAX5089)
♦ Integrated 150mΩ High-Side n-Channel Power
MOSFET
♦ Power-On Reset Output (MAX5088)/Power-Good
Output (MAX5089)
♦ Short-Circuit Protection
♦ Thermal-Shutdown Protection
♦ Thermally Enhanced 16-Pin TQFN Package
Dissipates 2.7W
Ordering Information
PART
TEMP RANGE
PIN-
PACKAGE
PKG
CODE
MAX5088ATE+ -40°C to +125°C
MAX5089ATE+ -40°C to +125°C
+Denotes lead-free package.
16 TQFN
16 TQFN
T1655-2
T1655-2
Pin Configurations
TOP VIEW
12 11 10 9
Selector Guide
PART
MAX5088ATE
CONFIGURATION
Nonsynchronous
Buck
MAX5089ATE Synchronous Buck
FEATURES
RESET Output,
Clock Output
PGOOD Output,
Synchronous FET
Driver
SYNC 13
RESET 14
BST/VDD 15
EN 16
MAX5088
+ EP*
1234
8 VL
7 V+
6 BYPASS
5 OSC
Pin Configurations continued at end of data sheet.
*EXPOSED PAD.
THIN QFN
5mm x 5mm
________________________________________________________________ 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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2.2MHz, 2A Buck Converters with an
Integrated High-Side Switch
Typical Operating Characteristics
(V+ = VL = 5.2V, TA = +25°C, Figures 5 and 6, unless otherwise noted.)
MAX5088 BUCK EFFICIENCY vs. OUTPUT
CURRENT (VIN = 5V, fSW = 2.2MHz)
90
3.3V
80
70 2.5V
60
50
40
30
20
10
0
0 500 1000 1500 2000 2500
OUTPUT CURRENT (mA)
MAX5088 BUCK EFFICIENCY vs. OUTPUT
CURRENT (VIN = 12V, fSW = 2.2MHz)
80
3.3V
70
60 2.5V
50
40
30
20
10
0
0 500 1000 1500 2000 2500
OUTPUT CURRENT (mA)
MAX5088 BUCK EFFICIENCY vs. OUTPUT
CURRENT (VIN = 16V, fSW = 2.2MHz)
70
60 3.3V
50
40
30
20
10
0
0 500 1000 1500 2000 2500
OUTPUT CURRENT (mA)
MAX5089 SYNCHRONOUS
EFFICIENCY vs. OUTPUT CURRENT
(VIN = 12V, fSW = 330kHz, L = 15µH)
95
90
3.3V
85
80
2.5V
75
70
1.2V
65
60
55
50
0
500 1000 1500 2000
OUTPUT CURRENT (mA)
2500
MAX5089 SYNCHRONOUS EFFICIENCY vs. OUTPUT
CURRENT (VIN = 12V, fSW = 2.2MHz, L = 4.7µH)
80
75 3.3V
70
65
60
55
50
45
40
35
30
0
500 1000 1500 2000
OUTPUT CURRENT (mA)
2500
MAX5089 OUTPUT VOLTAGE vs. OUTPUT
CURRENT (VIN = 12V, VOUT = 3.3V, fSW = 2.2MHz)
3.315
3.310
3.305
3.300
3.295
3.290
3.285
3.280
0
500 1000 1500
OUTPUT CURRENT (mA)
2000
5.190
5.185
5.180
5.175
5.170
5.165
5.160
5.155
5.150
100
VL OUTPUT VOLTAGE
vs. SWITCHING FREQUENCY
VIN = 23V
VIN = 5.5V
600 1100 1600 2100
SWITCHING FREQUENCY (kHz)
_______________________________________________________________________________________ 5
5 Page 
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2.2MHz, 2A Buck Converters with an
Integrated High-Side Switch
Detailed Description
PWM Controller
The MAX5088/MAX5089 use a pulse-width modulation
(PWM) voltage-mode control scheme. The MAX5088 is
a nonsynchronous converter and uses an external low-
forward-drop Schottky diode for rectification. The
MAX5089 is a synchronous converter and drives a low-
side, low-gate-charge MOSFET for higher efficiency.
The controller generates the clock signal from an inter-
nal oscillator or the SYNC input when driven by an
external clock. An internal transconductance error
amplifier produces an integrated error voltage at
COMP, providing high DC accuracy. The voltage at
COMP sets the duty cycle using a PWM comparator
and an internal 1VP-P voltage ramp. At each rising
edge of the clock, the converter’s high-side n-channel
MOSFET turns on and remains on until either the
appropriate or maximum duty cycle is reached or the
maximum current limit for the switch is detected.
MAX5088
During each high-side MOSFET on-time (Figure 5), the
inductor current ramps up. During the second half of
the switching cycle, the high-side MOSFET turns off and
forward biases the Schottky rectifier (D2 in Figure 5).
During this time, the SOURCE voltage is clamped to
0.5V below ground. The inductor releases the stored
energy as its current ramps down, and provides current
to the output. During the MOSFET off-time, when the
Schottky rectifier is conducting, the bootstrap capacitor
(C10 in Figure 5) is recharged from the VL output. At
light loads, the MAX5088 goes in to discontinuous con-
duction mode operation when the inductor current com-
pletely discharges before the next switching cycle
commences. When the MAX5088 operates in discontin-
uous conduction, the bootstrap capacitor can become
undercharged. To prevent this, an internal low-side 30Ω
switch (see N3 in Figure 1) turns on, during the off-time,
once every 4 clock cycles. This ensures that the nega-
tive terminal of the bootstrap capacitor is pulled to
PGND often enough to allow it to fully charge to VL,
ensuring the internal power switch properly turns on.
The operation of the bootstrap capacitor wake-up
switch causes a small increase in the output voltage rip-
ple at light loads. Under overload conditions, when the
inductor current exceeds the peak current limit of the
internal switch, the high-side MOSFET turns off quickly
and waits until the next clock cycle.
MAX5089
The MAX5089 is intended for synchronous buck opera-
tion only. During the high-side MOSFET on-time, the
inductor current ramps up. When the MOSFET turns off,
the inductor reverses polarity and forward biases the
Schottky rectifier in parallel with the low-side synchro-
nous MOSFET. The SOURCE voltage is clamped to
0.5V below ground until the break-before-make time
(tBBM) of 25ns is over. After tBBM, the synchronous rec-
tifier MOSFET turns on. The inductor releases the
stored energy as its current ramps down, and contin-
ues providing current to the output. The bootstrap
capacitor is also recharged from the VL output when
the MOSFET turns off. The synchronous rectifier keeps
the circuit in continuous conduction mode operation
even at light load. Under overload conditions, when the
inductor current exceeds the peak current limit of the
internal switch, the high-side MOSFET turns off and
waits until the next clock cycle.
The MAX5089, with the synchronous rectifier driver out-
put (DL), has an adaptive break-before-make circuit to
avoid cross conduction between the internal power
MOSFET and the external synchronous rectifier MOSFET.
When the synchronous rectifier MOSFET is turning off,
the internal high-side power MOSFET is kept off until
VDL falls below 0.97V. Similarly, DL does not go high
until the internal power MOSFET gate voltage falls
below 1.24V.
Input Voltage (V+)/Internal Linear
Regulator (VL)
All internal control circuitry operates from an internally
regulated nominal voltage of 5.2V (VL). At higher input
voltages (V+) of 5.5V to 23V, VL is regulated to 5.2V. At
5.5V or below, the internal linear regulator operates in
dropout mode, where VL follows V+. Depending on the
load on VL, the dropout voltage can be high enough to
reduce VL to below the undervoltage lockout (UVLO)
threshold.
For input voltages of lower than 5.5V, connect V+ and
VL together. The load on VL is proportional to the
switching frequency of the converter. See the VL
Output Voltage vs. Switching Frequency graph in the
Typical Operating Characteristics. For an input voltage
higher than 5.5V, use the internal regulator.
Bypass V+ to SGND with a low-ESR 0.1µF or greater
ceramic capacitor placed as close as possible to the
MAX5088/MAX5089. Current spikes from VL disturb the
internal circuitry powered by VL. Bypass VL with a low-
ESR 0.1µF ceramic capacitor to PGND and a low-ESR
4.7µF ceramic capacitor to SGND.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet MAX5089.PDF ] | |
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