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PDF MAX15021 Data sheet ( Hoja de datos )
| Número de pieza | MAX15021 | |
| Descripción | Step-Down DC-DC Regulator | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-4106; Rev 0; 5/08
Dual, 4A/2A, 4MHz, Step-Down DC-DC
Regulator with Tracking/Sequencing Capability
www.datasheet4u.com
General Description
The MAX15021 is a dual-output, pulse-width-modulated
(PWM), step-down DC-DC regulator with tracking (coin-
cident and ratiometric) and sequencing options. The
device operates from 2.5V to 5.5V and each output can
be adjusted from 0.6V to the input supply (VAVIN). The
MAX15021 delivers up to 4A (regulator 1) and 2A (reg-
ulator 2) of output current. This device offers the ability
to adjust the switching frequency from 500kHz to 4MHz
and provides the capability of optimizing the design in
terms of size and performance.
The MAX15021 utilizes a voltage-mode control scheme
with external compensation to provide good noise
immunity and maximum flexibility in selecting inductor
values and capacitor types. The dual switching regula-
tors operate 180° out-of-phase, thereby reducing the
RMS input ripple current and thus the size of the input
bypass capacitor significantly.
The MAX15021 offers the ability to track (coincident or
ratiometric) or sequence during power-up and power-
down operation. When sequencing, it powers up glitch-
free into a prebiased output.
Additional features include an internal undervoltage
lockout with hysteresis and a digital soft-start/soft-stop
for glitch-free power-up and power-down. Protection
features include lossless cycle-by-cycle current limit,
hiccup-mode output short-circuit protection, and ther-
mal shutdown.
The MAX15021 is available in a space-saving, 5mm x
5mm, 28-pin TQFN-EP package and is specified for
operation from -40°C to +125°C temperature range.
Applications
RFID Reader Cards
Power-over-Ethernet (PoE) IP Phones
Automotive Multimedia
Multivoltage Supplies
Networking/Telecom
Ordering Information
PART
MAX15021ATI+
TEMP RANGE
-40°C to +125°C
+Denotes a lead-free package.
*EP = Exposed pad.
PIN-PACKAGE
28 TQFN-EP*
Features
o 2.5V to 5.5V Input-Voltage Range
o Dual-Output Synchronous Buck Regulators
o Integrated Switches for 4A and 2A Output
Currents
o 180° Out-Of-Phase Operation
o Output Voltage Adjustable from 0.6V to VAVIN
o Lossless, Cycle-by-Cycle Current Sensing
o External Compensation for Maximum Flexibility
o Digital Soft-Start and Soft-Stop for Tracking
Applications
o Digital Soft-Start into a Prebiased Load for
Sequencing Applications
o Sequencing or Coincident/Ratiometric Tracking
o Programmable Switching Frequency from 500kHz
to 4MHz
o Thermal Shutdown and Hiccup-Mode Short-
Circuit Protection
o 20µA Shutdown Current
o 100% Maximum Duty Cycle
o Space-Saving (5mm x 5mm) 28-Pin TQFN
Package
Pin Configuration
TOP VIEW
21 20 19 18 17 16 15
N.C. 22
COMP2 23
FB2 24
EN2 25
SGND 26
AVIN 27
RT 28
+
MAX15021
*EP
14 N.C.
13 N.C.
12 COMP1
11 FB1
10 EN1
9 DVDD1
8 PGND1
1 234567
*EP = EXPOSED PAD.
THIN QFN
(5mm x 5mm)
________________________________________________________________ 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  
Dual, 4A/2A, 4MHz, Step-Down DC-DC
Regulator with Tracking/Sequencing Capability
www.datasheet4u.com
Typical Operating Characteristics (continued)
(VAVIN = VDVDD1 = VDVDD2 = VPVIN1 = VPVIN2 = 5V, VOUT1 = 3.3V, VOUT2 = 1.5V, VPGND_ = 0V, RT = 16.5kΩ. TA = +25°C, unless
otherwise noted.)
QUIESCENT CURRENT
vs. TEMPERATURE
5.00
4.75
4.50
4.25
4.00
3.75
3.50
3.25
3.00
2.75 NO SWITCHING
2.50
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
SWITCHING CURRENT
vs. TEMPERATURE
27
26
25
24 REGULATOR 1 ENABLED
23 VOUT1 = 3.3V
22
21
20
19
18
17
16 REGULATOR 2 ENABLED
15 VOUT2 = 1.5V
14
13
12
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
NORMALIZED UNDERVOLTAGE LOCKOUT
THRESHOLD vs. TEMPERATURE
1.030
1.025
1.020
1.015
1.010
1.005
1.000
0.995
0.990
0.985
0.980
0.975
VUVLO (NOM) = 2.2V
0.970
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
EN_ THRESHOLD
vs. TEMPERATURE
1.260
1.255
1.250
1.245
1.240
1.235
1.230
1.225
1.220
1.215
1.210
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
COINCIDENT TRACKING SOFT-START
MAX15021 toc13
VAVIN
5V/div
0V
VOUT1
1V/div
VOUT2
1V/div
0V
COINCIDENT TRACKING SOFT-STOP
MAX15021 toc14
VAVIN
5V/div
0V
VOUT1
EN1
VOUT2
1V/div
0V
1ms/div
400μs/div
_______________________________________________________________________________________ 5
5 Page 
Dual, 4A/2A, 4MHz, Step-Down DC-DC
Regulator with Tracking/Sequencing Capability
www.datasheet4u.com
Coincident/Ratiometric Tracking
The enable inputs in conjunction with digital soft-start
and soft-stop provide coincident/ratiometric tracking.
Track an output voltage by connecting a resistive
divider from the output being tracked to its enable
input. For example, for VOUT2 to coincidentally track
VOUT1, connect the same resistive divider used for
FB2, from VOUT1 to EN2 to SGND (see Figure 2).
Track ratiometrically by connecting EN_ to SGND. This
synchonizes the soft-start and soft-stop of all the regu-
lator references, and hence their respective output volt-
ages will track ratiometrically (see Figure 2).
When the MAX15021 regulators are configured as volt-
age trackers, output short-circuit fault conditions at
either master or slave output are handled carefully—nei-
ther the master nor slave output will remain energized
when the other output is shorted to ground. When the
slave is shorted and enters hiccup mode, the master will
soft-stop. When the master is shorted and the part
enters in hiccup mode, the slave will ratiometrically soft-
stop. Coming out of hiccup mode, both outputs will soft-
start coincidently or ratiometrically depending on their
initial configuration. During the thermal shutdown or
power-off when the input falls below its UVLO, the out-
put voltages decrease at a rate depending on the
respective output capacitance and load.
See Figure 1 for a graphical representation of coinci-
dent/ratiometric tracking.
Sequencing
When sequencing, the voltage at the enable inputs
must exceed 1.225V (typ) for each PWM controller to
start (see Figure 1c).
RATIOMETRIC TRACKING
VRIN1
COINCIDENT TRACKING
VRIN1
COINCIDENT TRACKING
VRIN2
EN1 EN1
EN2
EN2
SEL AVIN
OUTPUT 1 IS THE MASTER AND
OUTPUT 2 IS THE SLAVE.
VRIN2
EN2
EN1
VOUT1
EN2
VOUT2
FB2
RA
RB
RA
RB
VOUT2
EN1
VOUT1
FB1
RC
RD
RC
RD
SEL UNCONNECTED
OUTPUT 2 IS THE MASTER AND
OUTPUT 1 IS THE SLAVE.
SEL AVIN
OUTPUT 1 IS THE MASTER AND
OUTPUT 2 IS THE SLAVE.
Figure 2. Ratiometric Tracking and Coincident Tracking Configurations
SEL UNCONNECTED
OUTPUT 2 IS THE MASTER AND
OUTPUT 1 IS THE SLAVE.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 23 Páginas | |
| PDF Descargar | [ Datasheet MAX15021.PDF ] | |
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