DATASHEET
ISL6558
Multi-Purpose Precision Multi-Phase PWM Controller With Optional Active Voltage
Positioning
The ISL6558 is a multi-phase PWM 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.
FN9027
Rev 13.00
August 28, 2015
Features
•
Pb-Free Plus Anneal Available (RoHS Compliant)
• 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 -40
°
C - 85
°
C Range
- 0. 8V ± 1.0% Over 0
°
C - 70
°
C 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
Pinouts
ISL6558 (16 LEAD SOIC)
TOP VIEW
ISL6558 (20 LEAD 5X5 QFN)
TOP VIEW
PGOOD
PWM4
V
CC
1
PGOOD 2
COMP 3
DROOP 4
FB 5
VSEN 6
FS/EN 7
GND 8
16 PWM4
15 ISEN4
14 ISEN1
13 PWM1
12 PWM2
10 ISEN3
COMP
N/C
1
2
3
4
5
20
19
18
17
16
15 ISEN1
14 PWM1
13 PWM2
12 ISEN2
11 ISEN3
11 ISEN2 DROOP
9 PWM3
FB
VSEN
6
N/C
7
FS/EN
8
GND
9
GND
10
PWM3
FN9027 Rev 13.00
August 28, 2015
Page 1 of 17
ISEN4
VCC
VCC
ISL6558
Functional Pin Description
NOTE: Pin numbers refer to the SOIC package. Check PINOUT
diagrams for QFN pin numbers.
FS/EN (Pin 7)
Connecting a resistor from this pin to ground sets the
internal oscillator frequency. The switching frequency, F
SW
,
of the converter is adjustable between 80kHz and 1.5MHz.
Pulling this pin to ground disables the converter and three-
states the PWM outputs.
VCC (Pin 1)
Supplies all the power necessary to operate the chip. The IC
starts to operate when the voltage on this pin exceeds the
rising POR threshold and shuts down when the voltage on
this pin drops below the falling POR threshold. Connect this
pin to a 5V (±5%) supply.
GND (Pin 8)
Bias and reference ground for all controller signals.
PGOOD (Pin 2)
Power good is an open drain output used to indicate the
status of the output voltage. This pin is pulled low when the
converter output voltage is either 10% below or 15% above
the reference voltage.
PWM1 (Pin 13), PWM2 (Pin 12), PWM3 (Pin 9),
PWM4 (Pin 16)
The controller PWM drive signals are connected to the
individual HIP660x driver PWM input pins. The number of
active channels is determined by the state of PWM3 and
PWM4. If PWM3 is tied to VCC, this indicates to the
controller that two channel operation is desired. In this case,
PWM4 should be left open or tied to VCC. Tying PWM4 to
VCC indicates that three channel operation is desired.
COMP (Pin 3)
Output of the internal error amplifier. Connect this pin to the
external feedback compensation network.
DROOP (Pin 4)
Output voltage droop or active voltage positioning is
provided by connecting this pin to the FB pin. An internal
current source creates the droop across an external
feedback resistor, R
FB
. If no droop is desired, this pin MUST
be left open.
ISEN1 (Pin 14), ISEN2 (Pin 11), ISEN3 (Pin 10),
ISEN4 (Pin 15)
These pins are used to monitor the voltage drop across the
lower MOSFETs for current feedback, output voltage droop
and overcurrent protection. A resistor must be placed in
series with each of these inputs and their respective PHASE
node. The resistor is sized such that the current feedback is
50A at full load. Sense lines corresponding to inactive
channels should be left open. Inactive channels are those in
which the PWM pin has been tied to VCC or left open.
FB (Pin 5)
The FB pin is the inverting input of the internal error
amplifier. Connect this pin to the external feedback
compensation network and a resistor divider from the output
for proper control and protection of converter load.
Thermal Pad (in QFN only)
In the QFN package, the pad underneath the center of the
IC is a thermal substrate. The PCB “thermal land” design
for this exposed die pad should include thermal vias that
drop down and connect to one or more buried copper
plane(s). This combination of vias for vertical heat escape
and buried planes for heat spreading allows the QFN to
achieve its full thermal potential. This pad should be either
grounded or floating, and it should not be connected to
other nodes. Refer to TB389 for design guidelines.
VSEN (Pin 6)
This pin is connected through a resistor divider to the
converter’s output voltage to provide remote sensing. The
undervoltage and overvoltage protection comparators trigger
off this input.
FN9027 Rev 13.00
August 28, 2015
Page 4 of 17
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