ISL6446A Datasheet, PDF (1/20 Pages) Intersil Corporation – Dual (180°Out-of-Phase) PWM and Linear Controller

Dual (180°Out-of-Phase) PWM and Linear Controller
ISL6446A
The ISL6446A 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 is 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
pre-biased load.
The ISL6446A incorporates robust protection features. An
adjustable overcurrent protection circuit monitors the output
current by sensing the voltage drop across the upper MOSFET
r_DS(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 shut-down 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 pre-biased 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
C_VCC
R_OCSET1
VCC
COMP1
FB1
VIN
OCSET1 _CBOOT1
BOOT1
UGATE1
VIN1 = VIN
C_OCSET1
C_IN1
Q₁
COMP2
FB2
PHASE1
LGATE1
L₁
Q₂
VOUT1
C_OUT1
ISL6446A
R_OCSET2
OCSET2 _CBOOT2
BOOT2
VIN2 = VIN
C_OCSET2
C_IN2
PGOOD
RT
SS/EN1
SS/EN2
UGATE2
PHASE2
LGATE2
LCDR
LCFB
Q₃
L₂
Q₄
VOUT2
C_OUT2
SGND PGND
FIGURE 1. TYPICAL APPLICATION
100
98
96
94
92
90
V_OUT = 3.3V
V_OUT = 5V
88
86
84
82
80
0
5
10
15
20
25
LOAD CURRENT (A)
FIGURE 2. EFFICIENCY vs LOAD CURRENT (Obtained from
ISL6446AEVAL1Z)
November 6, 2012
1
FN8384.1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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