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PDF ISL6446 Data sheet ( Hoja de datos )
| Número de pieza | ISL6446 | |
| Descripción | Dual PWM and Linear Controller | |
| Fabricantes | Intersil | |
| Logotipo |  |
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DATASHEET
Dual (180°Out-of-Phase) PWM and Linear Controller
ISL6446
The ISL6446 is a high-performance, triple output controller
that provides a single high-frequency power solution primarily
for broadband, DSL and networking applications. This device
integrates complete control, monitoring and protection
functions for two synchronous buck PWM controllers and one
linear controller. Input voltage ripple and total RMS input
current is substantially reduced by synchronized 180°
out-of-phase operation of the two PWMs.
The two PWM buck converters provide simple voltage mode
control. The output voltage of the converters can be precisely
regulated to as low as 0.6V, with a maximum tolerance of
±1.5% over-temperature and line variations. Programmable
switching frequency down to 100kHz provides optimized low
cost solution for ATX power supplies. It’s also able to operate
up to 2.5MHz to deliver compact solutions. The linear
controller provides a low-current output.
Each PWM controller has soft-start and independent enable
functions combined on a single pin. A capacitor from SS/EN to
ground sets the soft-start time; pulling SS/EN pin below 1V
disables the controller. Both outputs can soft-start into a
prebiased load.
The ISL6446 incorporates robust protection features. An
adjustable overcurrent protection circuit monitors the output
current by sensing the voltage drop across the upper MOSFET
rDS(ON). Latch-off mode overcurrent operation protects the
DC/DC converters from damage under overload and
short-circuit conditions. A PGOOD signal is issued when
soft-start is complete and PWM outputs are within 10% of
their regulated values and the linear regulator output is higher
than 75% of its nominal value. Thermal shutdown circuitry
turns the device off if the IC temperature exceeds +150°C.
Features
• 4.5V to 5.5V or 5.5V to 24V input voltage range
• Three programmable power output voltages
- Two PWM controllers with out-of-phase operation
- Voltage-mode PWM control
- One linear controller
• Programmable switching frequency from 100kHz to 2.5MHz
• Fast transient response
- High-bandwidth error amplifier
• Extensive circuit protection functions
- Undervoltage and over-temperature
- Overvoltage with latch-off mode
- Programmable overcurrent limit with latch-off mode
- Lossless current sensing (no sense resistor needed)
• Externally adjustable soft-start time
- Independent enable control
- Voltage tracking capability
- Able to soft-start into a prebiased load
• PGOOD output with delay
Applications
• ATX power supplies
• DSP, ASIC and FPGA point of load regulation
• Industrial and security networking applications
VOUT1
VOUT2
Feedback
and
Compensation
Network
R1
Feedback
and
Compensation
Network
R2
VCC VIN
CVCC
ROCSET1
VCC
COMP1
FB1
VIN
OCSET1
BOOT1
UGATE1
CBOOT1
Q1
VIN1 = VIN
COCSET1
CIN1
COMP2
PHASE1
LGATE1
Q2
L1
VOUT1
COUT1
FB2
ISL6446
ROCSET2
VIN2 = VIN
OCSET2
BOOT2
UGATE2
CBOOT2
Q3
COCSET2
CIN2
PGOOD
PHASE2
LGATE2
Q4
L2
VOUT2
COUT2
RT
SS1/EN1
SS2/EN2
LCDR
LCFB
SGND PGND
FIGURE 1. TYPICAL APPLICATION
100
98
96
94
92
90 VOUT = 3.3V
VOUT = 5V
88
86
84
82
80 0 5 10 15 20 25
LOAD CURRENT (A)
FIGURE 2. EFFICIENCY vs LOAD CURRENT (OBTAINED FROM
ISL6446EVAL1Z)
October 12, 2015
FN7944.2
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Copyright Intersil Americas LLC 2012, 2013, 2015. All Rights Reserved
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
1 page  
ISL6446
Typical Application Schematic
VOLTAGE INPUTS REQUIRED
VIN (4.5V TO 24V) = VIN1 = VIN2
VCC (5V; INTERNAL IF VIN > 5.6V)
VIN3 (VCC) FOR LINEAR
TYPE-3 COMPENSATION SHOWN
C102
VOUT1
R102 C101
R101
R103
C103
C202
R100
VOUT2
R202 C201
R201
R203 C203
R200
TYPE-3 COMPENSATION SHOWN
VCC
RPGOOD
VCC
VCC
CVCC CVIN
VIN
OPTIONAL
CONNECTION
(FOR VIN = VCC = 5V)
ROCSET1
VIN
VIN1 = VIN
COMP1
FB1
OCSET1
BOOT1
COCSET1
CBOOT1
Q101
CIN1
UGATE1
PHASE1
0.9µH
L100
VOUT1
COMP2
FB2
ISL6446
LGATE1
Q102
2x680µF/18m
2x100µF
1x47µF
ROCSET2
VIN2 = VIN
COUT1
OCSET2
BOOT2
UGATE2
PHASE2
LGATE2
COCSET2
CBOOT2
Q201
CIN2
0.9µH
L200
Q202
VOUT2
COUT2
2x680µF/18m
2x100µF
PGOOD
RT
SS1/EN1
SS2/EN2
LCDR
R304
R303
C301
R302
Q301
VIN3
CIN3
CSS1/EN1 CSS2/EN2
RRT
SGND
PGND
LCFB
R300
R301
VOUT3
COUT3
FIGURE 4. ISL6446 TYPICAL APPLICATION
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FN7944.2
October 12, 2015
5 Page 
ISL6446
Typical Performance Curves Oscilloscope plots are taken using the ISL6446EVAL1Z evaluation board, VIN = 12V,
VOUT1 = 5V, VOUT2 = 3.3V, fSW = 300kHz, unless otherwise noted. (Continued)
VIN = 12V
VOUT1 = 5V
IOUT = S/C
EN/SSx
VIN = 12V
VOUT1 = 5V
IOUT = 10, FB = 1V
EN/SSx
VOUT
IL
VOUT
IL
PHASE
PHASE
FIGURE 16. START-UP WITH OC
Functional Description
Soft-Start and Voltage Tracking
After the VCC pin exceeds its rising POR trip point (nominal 4.4V),
the chip operation begins. Both 30µA current sources will start
charging up the soft-starting capacitors respectively. The charging
continues until the voltage across the soft-start capacitor reaches
about 3.2V. From 1.0V to 1.6V, the outputs will ramp individually
from zero to full-scale. Now, if V = 0.6V, C = 0.1µF, and I = 30µA,
then t = 2ms. Figure 18 shows the typical waveforms for SS2/EN2
and VOUT2; SS1/EN1 and VOUT1 are similar (see Figure 19).
SS2/EN2 (0.5V/DIV)
1.6V
1.0V
VOUT2 (2V/DIV)
GND>
FIGURE 18. SOFT-START
The soft-start ramps for each output can be selected
independently. The basic timing is shown in Equation 2:
t = C d----IV---
Where:
t is the charge time
C is the external capacitance
dV is the voltage charged
I is the charging current (nominal 30µA)
(EQ. 2)
FIGURE 17. OVERVOLTAGE PROTECTION
Finally, there is a delay after 1.6V, until the ramp gets to ~3.2V,
which signals that the ramp is done; when both ramps are done,
the PGOOD delay begins. To guarantee the soft-start is
completed, please make sure the EN/SSx pin voltage is able to
reach above 3.2V at normal operation.
VOUT2 (1V/DIV)
GND>
1.6V
1.0V
SS1/EN1 (0.5V/DIV)
VOUT (1V/DIV)
SS2/EN2 (0.5V/DIV)
GND>
FIGURE 19. VOLTAGE TRACKING
Figure 20 shows prebiased outputs before soft-start. The solid
blue curve shows no prebias; the output starts ramping from
GND. The magenta dotted line shows the output prebiased to a
voltage less than the final output. The FETs don’t turn on until the
soft-start ramp voltage exceeds the output voltage; then the
output starts ramping seamlessly from there. The cyan dotted
line shows the output prebiased above the final output (but
below the OVP (Overvoltage Protection)). The FETs will not turn on
until the end of the soft-start ramp; then the output will be
quickly pulled down to the final value.
If the output is prebiased above the OVP level, the ISL6446 will go
into OVP at the end of soft-start, which will keep the FETs off. See
“Protection Mechanisms” on page 13 for more details.
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FN7944.2
October 12, 2015
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet ISL6446.PDF ] | |
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