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PDF ISL6558 Data sheet ( Hoja de datos )
| Número de pieza | ISL6558 | |
| Descripción | Multi-Purpose Precision Multi-Phase PWM Controller With Optional Active Voltage Positioning | |
| Fabricantes | Intersil Corporation | |
| Logotipo |  |
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®
Data Sheet
December 2003
ISL6558
FN9027.6
Multi-Purpose Precision Multi-Phase PWM
Controller With Optional Active Voltage
Positioning
The ISL6558 is a multi-phase PWM
TM controller, which in combination with
the HIP6601B, HIP6602B,
HIP6603B, or ISL6605 companion
gate drivers form a complete solution for high-current, high
slew-rate applications. The ISL6558 regulates output
voltage, balances load currents and provides protective
functions for two to four synchronous rectified buck
converter channels.
A novel approach to current sensing is used to reduce
overall solution cost and improve efficiency. The voltage
developed across the lower MOSFET during conduction is
sampled and fed back to the controller. This lossless
current-sensing approach enables the controller to maintain
phase-current balance between the power channels, provide
overcurrent protection, and permit droop compensation.
Optional output voltage “droop” or active voltage positioning
is supported via the DROOP pin. Taking advantage of this
feature reduces the size and cost of the output capacitors
required to support a load transient.
In the event of an overvoltage, the controller monitors and
responds to reduce the risk of damage to load devices.
Undervoltage conditions are indicated through a PGOOD
transition. Overcurrent conditions cause the converter to
shutdown limiting the exposure of load devices. These
integrated monitoring and protection features provide a safe
environment for microprocessors and other advanced low
voltage circuits.
Ordering Information
PART NUMBER TEMP. (oC) PACKAGE PKG. DWG. #
ISL6558CB
0 to 70
16 Ld SOIC
M16.15
ISL6558CB-T
16 Ld SOIC Tape and Reel
ISL6558CR
0 to 70 20 Ld 5x5 QFN L20.5X5
ISL6558CR-T
20 Ld QFN Tape and Reel
ISL6558IB
-40 to 85 16 Ld SOIC
M16.15
ISL6558IB-T
16 Ld SOIC Tape and Reel
ISL6558IR
-40 to 85 20 Ld 5x5 QFN L20.5X5
ISL6558IR-T
20 Ld QFN Tape and Reel
ISL6558EVAL1 Evaluation Platform 1 (SOIC Package,
ISL6558CB + HIP6601BCB)
ISL6558EVAL2 Evaluation Platform 2 (QFN Package,
ISL6558CR + ISL6605CR)
Features
• Multi-Phase Power Conversion
- 2-, 3-, or 4-Phase Operation
• Optional Output Voltage Droop
• Precision Channel-Current Balance
• Lossless Current Sensing
• Precision Reference Voltage
- 0.8V±1.5% Over -40oC - 85oC Range
- 0. 8V± 1.0% Over 0oC - 70oC Range
• Fast Transient Response
• Overcurrent and Overvoltage Protection
• Digital Soft-start
• Power Good Indication
• High Ripple Frequency (80kHz to 1.5MHz)
• QFN Package
- Compliant to JEDEC PUB95 MO-220 QFN-Quad Flat
No Leads-Product Outline
- Near Chip-Scale Package Footprint; Improves PCB
Efficiency and Thinner in Profile
Applications
• Power Supply Control for Microprocessors
• Low Output Voltage, High Current DC-DC Converters
• Voltage Regulator Modules
• Servers and Workstations
• Memory and Accelerated Graphics Port Supplies
• Communication Processor and Personal Computer
Peripherals
1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2003. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
1 page  
ISL6558
Typical Application - 3 Phase Converter
VOUT = 0.8V(RFB + ROS)/ROS
RFB
RC +5V
RFB
ROS
ROS
CC
FB DROOP COMP
VSEN
VCC
PGOOD
PWM4
PWM3
PWM2
PWM1
PWM
CONTROL
ISL6558
ISEN4 NC
FS/EN
RT
ISEN3
ISEN2
GND
ISEN1
+5V
PVCC
BOOT
UGATE
VCC
PHASE
PWM
DRIVER
HIP6601B
LGATE
GND
+5V
PVCC
BOOT
UGATE
VCC
PWM
PHASE
DRIVER
HIP6601B
LGATE
GND
+5V
PVCC
BOOT
UGATE
VCC
PWM
DRIVER
HIP6601B
PHASE
LGATE
GND
+12V
RISEN3
+12V
VOUT
RISEN2
+12V
RISEN1
5
5 Page 
ISL6558
See Figure 6. ITOTAL is compared with an internally
generated overcurrent trip current, ITRIP. The overcurrent
trip current source is trimmed to 82.5µA. If ITOTAL exceeds
the ITRIP level, then the controller forces all PWM outputs
into three-state. This condition results in the HIP660x gate
drivers removing drive to the MOSFETs. The VSEN voltage
will begin to fall and once it descends below the PGOOD falling
threshold, the PGOOD signal transitions low.
A delay time, equal to the soft-start interval, is entered to
allow the disturbance to clear. After the delay time, the
controller then initiates a second soft-start interval. If the
output voltage comes up and regulation is achieved,
PGOOD transitions high. If the OC trip current is exceeded
during the soft start interval, the controller will again shut
down PWM operation and three-state the drivers. The
PGOOD signal will remain low and the soft-start interval will
be allowed to expire. Another soft-start interval will be
initiated after the delay interval. If an overcurrent trip occurs
again, this same cycle repeats until the fault is removed. The
OC function is shown in Figure 7 for a hard short of the
output which is applied for only a brief moment. The
converter quickly detects the short and attempts to restart
twice before the short is removed.
Overcurrent protection reduces the regulator RMS output
current under worst case conditions to 95% of the full load
current.
SELECTING RISEN
The procedure for determining the value of RISEN is to
insure that it scales a channel’s maximum output current to
50µA. This will insure that the overcurrent trip point is
properly detected when a current limit of 165% of the
converter’s full load current is breached. The ISEN resistor
can be calculated as follows:
RISEN
=
I--F-----L-
n
x
r---D---5-S--0---(-µ-O---A---N----)-
(EQ. 6)
where IFL is the maximum output current demanded by the
load device and ‘n’ is the number of active channels.
OC TRIP LEVEL ADJUSTMENT
Setting the full load reference current, ITOTAL, to 50µA is
recommended for most applications. The ratio between the
desired full load reference current and the internally set
overcurrent trip current is the overcurrent trip ratio, KOC. For
those applications where an OC trip level of 1.65 times
ITOTAL is insufficient, the full load reference current can be
scaled differently. Care must be taken in selection of certain
components once the desired OC trip ratio is determined.
KOC
=
--8---2----.-5----µ----A----
ITOTAL
(EQ. 7)
The new overcurrent trip ratio is then used to calculate the
ISEN resistors for the new full load reference current.
RISEN
=
I--F-----L-
n
x
r---D----S-----(8--O--2---.-N-5---µ)---x-A--K----O------C--
(EQ. 8)
One commonly over looked component which will change
due to the new overcurrent trip ratio is the feedback resistor,
RFB.
RFB = V-----D-----R---8-O---2---O.--5---Pµ----xA----K----O-----C---
(EQ. 9)
Temperature effects of the MOSFET rDS(ON) must be
reviewed when changing the overcurrent trip level.
Output Voltage Monitoring
The output voltage must be tied to the VSEN pin to provide
feedback used to create a window of operation. If the output
voltage is not the reference voltage of 0.8V, it must be
scaled externally down to this level. The VSEN voltage is
then compared with two set voltage levels which indicate an
overvoltage or undervoltage condition of the output.
Violating either of these conditions results in the PGOOD pin
output toggling low to indicate a problem with the output
voltage.
OVERVOLTAGE
The VSEN voltage is compared with an internal overvoltage
protection (OVP) reference set to 115% of the internal
reference. If the VSEN voltage exceeds the OVP reference,
the comparator simultaneously sets the OV latch and
triggers the PWM output low. The drivers turn on the lower
MOSFETs, shunting the converter output to ground. Once
the output voltage falls below the nominal output voltage, the
PWM outputs are placed in three-state. This prevents
dumping of the output capacitors back through the lower
MOSFETs. If the overvoltage conditions persist, the PWM
outputs are cycled between the two states similar to a
hysteretic regulator. The OV latch can only be reset by
cycling the VCC supply voltage to initiate a POR and begin a
soft-start interval.
UNDERVOLTAGE
The VSEN voltage is also compared to a undervoltage (UV)
reference which is set to 90% of the internal reference. If the
VSEN voltage is below the UV reference, the power good
monitor triggers PGOOD to go low. The UV comparator does
not influence converter operation.
VSEN SCALING
The output voltage, VOUT, must be fed back to the VSEN pin
separately from the feedback components to the FB pin. If
VSEN and FB are tied together, the error amplifier will hold
the VSEN voltage at the reference level while the actual
output voltage level could be much different. This would
mask the output voltage and prevent the protection features
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet ISL6558.PDF ] | |
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