Intersil ISL6219ACAZ Microprocessor core voltage regulator precision multi-phase buck pwm controller for mobile application Datasheet

ISL6219A
®
Data Sheet
March 20, 2007
Microprocessor CORE Voltage Regulator
Precision Multi-Phase BUCK PWM
Controller for Mobile Applications
The ISL6219A provides core-voltage regulation by driving up
to three interleaved synchronous-rectified buck-converter
channels in parallel. Intersil multi-phase controllers together
with ISL6207 gate drivers form the basis for the most reliable
power-supply solutions available to power the latest
industry-leading microprocessors. Multi-phase buck-converter
architecture uses interleaved timing to multiply ripple
frequency and reduce input and output ripple currents. Lower
ripple results in lower total component cost, reduced
dissipation, and smaller implementation area. Pre-configured
for 3-phase operation, the ISL6219A offers the flexibility of
2-phase operation. Simply connect the unused PWM pin to
+5V. The channel switching frequency is adjustable in the
range of 100kHz to 1.5MHz giving the designer the ultimate
flexibility in managing the balance between high-speed
response and good thermal management.
New features on the ISL6219A include Dynamic-VID™
technology allowing seamless on-the-fly VID changes with
no need for any additional external components. When the
ISL6219A receives a new VID code, it incrementally steps
the output voltage to the new level. Dynamic VID™ changes
are fast and reliable with no output voltage overshoot or
undershoot.
FN9093.1
Features
• Multi-Phase Power Conversion
• Active Channel Current Balancing
• Lossless current sense scheme
- Uses MOSFET’s rDS(ON)
- Optional current sense method for higher precision
• Precision CORE Voltage Regulation
- ±0.8% System Accuracy Over Temperature
• Microprocessor Voltage Identification Input
- Dynamic VID technology
- 5-Bit VID Input
- 1.100V to 1.850V in 25mV Steps
• Programmable Droop Voltage
• Fast Transient Recovery Time
• Overvoltage, Undervoltage and Overcurrent Protection
• Power-Good Output
• 2 or 3 Phase Operation
• User selectable Switching Frequency of 100kHz to 1.5MHz
- 200kHz - 4.5MHz Effective Ripple Frequency
ISL6219A
(28 LD QSOP)
TOP VIEW
Like other Intersil multiphase controllers, the ISL6219A uses
cost and space-saving rDS(ON) sensing for channel current
balance and dynamic voltage positioning. Channel current
balancing is automatic and accurate with the integrated
current-balance control system. Overcurrent protection can be
tailored to any application with no need of additional parts.
An integrated DAC decodes the 5-bit logic signal present at
VID0-VID4 and provides an accurate reference for precision
voltage regulation. The high-bandwidth error amplifier and
accurate voltage reference all work together to provide
better than 0.8% total system accuracy, and to enable the
fastest transient response available. A window comparator
toggles PGOOD if the output voltage moves out of range
and acts to protect the load in case of overvoltage.
VID 0 1
28 VCC
VID 1 2
27 NC
VID 2 3
26 NC
VID 3 4
25 PGOOD
VID 4 5
24 NC
NC 6
23 ISEN1
FS/EN 7
22 PWM1
NC 8
21 PWM2
FB 9
20 ISEN2
COMP 10
19 ISEN3
NC 11
18 PWM3
NC 12
17 NC
NC 13
16 VSEN
GND 14
15 NC
Ordering Information
PART NUMBER
PART MARKING
TEMP. RANGE (°C)
PACKAGE
PKG. DWG. #
ISL6219ACA*
ISL 6219ACA
-10 to +85
28 Ld QSOP
M28.15
ISL6219ACAZ* (Note)
ISL6219 ACAZ
-10 to +85
28 Ld QSOP (Pb-free)
M28.15
*Add “-T” suffix for tape and reel.
NOTE: Intersil Pb-free plus anneal products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate
termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL
classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Dynamic VID is a trademark of Intersil Americas Inc. Copyright © Intersil Americas Inc. 2002, 2007. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
ISL6219A
Block Diagram
VCC
PGOOD
POWER-ON
RESET (POR)
VSEN
+
UV
-
X 0.83
THREE-STATE
OV
LATCH
+
CLOCK AND
SAWTOOTH
GENERATOR
+
OV
∑
-
X1.15
+
+
PWM1
PWM
-
SOFTSTART
AND FAULT
LOGIC
FS/EN
-
∑
+
PWM2
PWM
-
-
COMP
+
∑
+
-
VID0
PWM3
PWM
-
VID1
VID2
VID3
DYNAMIC
VID
D/A
+
E/A
-
VID4
CURRENT
FB
CORRECTION
PHASE
NUMBER
CHANNEL
DETECTOR
ISEN1
I_TOT
+
+
-
+
OC
+
ISEN2
∑
ISEN3
I_TRIP
GND
2
FN9093.1
March 20, 2007
ISL6219A
Typical Application - 3-Phase Buck Converter
+5V
VIN
VCC
BOOT
UGATE
EN
L1
PHASE
ISL6207
RFB
PWM1
RC
DRIVER
+5V
LGATE
GND
CC
FB
COMP
+5V
VIN
VCC
VSEN
VCC
PGOOD
EN
ISL6219A
ISL6207
DRIVER
PWM2
PWM1
VID1
LGATE
GND
PWM2
VID2
L2
PHASE
RISEN1
ISEN1
VID0
BOOT
UGATE
RISEN2
ISEN2
VID3
PWM3
VID4
RISEN3
+5V
VIN
ISEN3
FS/EN
µP
LOAD
RT
VCC
BOOT
UGATE
EN
GND
L3
PHASE
ISL6207
PWM3
DRIVER
LGATE
CO
GND
3
FN9093.1
March 20, 2007
ISL6219A
Functional Pin Descriptions
VID0, VID1, VID2, VID3, VID4 (Pins 1, 2, 3, 4, 5)
These are the inputs to the internal DAC that provide the
reference voltage for output regulation. Each pin has an
internal 20μA pull-up current source to 2.5V making the parts
compatible with CMOS and TTL logic from 5V down to 2.5V.
When a VID change is detected the reference voltage slowly
ramps up or down to the new value in 25mV steps. Connect
these pins to either open-drain or active-pull-up type outputs.
Pulling these pins above 2.9V can cause a reference offset
inaccuracy.
FS/EN (Pin 7)
GND (Pin 14)
Bias and signal ground for the IC.
VSEN (Pin 15)
Power good monitor input. Connect to the microprocessor
CORE voltage.
PWM3, PWM2, PWM1 (Pins 18, 21, 22)
Pulse-width modulation outputs. These logic outputs tell the
driver IC(s) when to turn the MOSFETs on and off.
ISEN3, ISEN2, ISEN1 (PINS 19, 20, 23)
This is a dual function pin. A resistor placed from FS/EN to
ground sets the switching frequency. There is an inverse
relationship between the value of the resistor and the
switching frequency. This pin can also be used to disable the
controller. To disable the controller, pull this pin below 1V.
Current sense inputs. A resistor connected between these
pins and the respective phase nodes has a current
proportional to the current in the lower MOSFET during its
conduction interval. The current is used as a reference for
channel balancing, load sharing, protection, and load-line
regulation.
FB (Pin 8) and COMP (Pin 9)
PGOOD (Pin 25)
The internal error amplifier’s inverting input and output
respectively. These pins are connected to an external R-C
network to compensate the regulator.
Power good. This pin is an open-drain logic signal that
indicates when the microprocessor CORE voltage (VSEN
pin) is within specified limits and soft-start has timed out.
VCC (Pin 28)
Bias supply voltage for the controller. Connect this pin to a
5V power supply.
4
FN9093.1
March 20, 2007
ISL6219A
Absolute Maximum Ratings
Thermal Information
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7V
Input, Output, or I/O Voltage . . . . . . . . . . GND -0.3V to VCC + 0.3V
ESD Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3kV
Thermal Resistance (Typical, Note 1)
Recommended Operating Conditions
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +5V ±5%
Ambient Temperature. . . . . . . . . . . . . . . . . . . . . . . . .-10°C to +85°C
θJA (°C/W)
SSOP Package (Note 1) . . . . . . . . . . . . . . . . . . . . .
76
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . +150°C
Maximum Storage Temperature Range . . . . . . . . . .-65°C to +150°C
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . +300°C
(SSOP - Lead Tips Only)
CAUTION: Stress above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational section of this specification is not implied.
+150°C max junction temperature is intended for short periods of time to prevent shortening the lifetime. Operation close to +150°C junction may trigger the shutdown of
the device even before +150°C, since this number is specified as typical.
NOTE:
1. θJA is measured with the component mounted on a high effective thermal conductivity test board in free air. (See Tech Brief TB379 for details.)
Electrical Specifications
Operating Conditions: VCC = 5V, TA = -10°C to +85°C, Unless Otherwise Specified
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
-
9.3
15
mA
RT = 100kΩ, FS/EN = 0V
4.5
8.8
14
mA
VCC Rising
4.25
4.38
4.5
V
VCC Falling
3.75
3.88
4.0
V
-0.8
-
0.8
%VID
VID Pull Up
-
2.5
-
V
VID Input Low Level
-
-
0.8
V
2.0
-
-
V
-20
-
20
%
280
336
kHz
1500
kHz
INPUT SUPPLY POWER
Input Supply Current
RT = 100kΩ, FS/EN = 1.23V
Power-On Reset Threshold
SYSTEM ACCURACY
System Accuracy
VID Input High Level (Note 3)
OSCILLATOR
Accuracy
Frequency
RT = 100kΩ (±1%)
224
Adjustment Range
Guaranteed by characterization
100
Disable Voltage
-
1.23
1.1
V
Sawtooth Amplitude
-
1.54
-
V
Duty-Cycle Range Functional
0
-
75
%
Open-Loop Gain
-
72
-
dB
Open-Loop Bandwidth
-
18
-
MHz
-
5.3
-
V/μs
ERROR AMPLIFIER
Slew Rate
CL = 100pF, RL = 10kΩ to ground
Maximum Output Voltage
RL = 10kΩ to ground
3.6
4.1
-
V
Minimum Output Voltage
RL = 10kΩ to ground
-
0.23
0.5
V
Full Scale Input Current
-
50
-
μA
Overcurrent Trip Level
-
75
-
μA
-
0.18
0.4
V
ISEN
POWER GOOD MONITOR
PGOOD Low Output Voltage
IPGOOD = 4mA
5
FN9093.1
March 20, 2007
ISL6219A
Electrical Specifications
Operating Conditions: VCC = 5V, TA = -10°C to +85°C, Unless Otherwise Specified (Continued)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
VSEN Rising
112
115
12
%VDAC
VSEN Falling
-
VID
-
%VDAC
VSEN Rising
85
92
95
%VDAC
VSEN Falling
80
83
90
%VDAC
PROTECTION and MONITOR
Overvoltage Threshold
Undervoltage Threshold
NOTES:
2. These parts are designed and adjusted for accuracy within the system tolerance given in the Electrical Specifications. The system tolerance
accounts for offsets in the differential and error amplifiers; reference-voltage inaccuracies; temperature drift; and the full DAC adjustment range.
3. VID input levels above 2.9V may produce an reference-voltage offset inaccuracy. Use a current limit resistor when pull up to 5V.
CC
RC
VIN
COMP
-
PWM1
-
+
PWM
CIRCUIT
+
ISEN1
RISEN1
-
DAC
&
REFERENCE
VIN
PWM
CIRCUIT
+
PWM2
-
L2
ISL6207
FB
PWM
CIRCUIT
+
ISL6207
ERROR
AMPLIFIER
L1
AVERAGE
IOUT
VOUT
ISEN2
CO
RISEN2
RFB
μP
LOAD
VIN
-
CURRENT
SENSE
PWM3
+
-
CURRENT
SENSE
-
CURRENT
SENSE
ISL6207
+
L3
+
ISL6219A
ISEN3
RISEN3
VSEN
FIGURE 1. SIMPLIFIED BLOCK DIAGRAM OF THE ISL6219A
6
FN9093.1
March 20, 2007
ISL6219A
Operation
To understand the reduction of ripple current amplitude in the
multi-phase circuit, examine the equation representing an
individual channel’s peak-to-peak inductor current.
Multi-Phase Power Conversion
Multi-phase power conversion provides the most costeffective power solution when load currents are no longer
easily supported by single-phase converters. Although its
greater complexity presents additional technical challenges,
the multi-phase approach offers cost-saving advantages with
improved response time, superior ripple cancellation, and
excellent thermal distribution.
INTERLEAVING
The switching of each channel in a multi-phase converter is
timed to be symmetrically out of phase with each of the other
channels. In a 3-phase converter, each channel switches 1/3
cycle after the previous channel and 1/3 cycle before the
following channel. As a result, the three-phase converter has
a combined ripple frequency three times greater than the
ripple frequency of any one phase. In addition, the peak-topeak amplitude of the combined inductor currents is reduced
in proportion to the number of phases (Equations 1 and 2).
Increased ripple frequency and lower ripple amplitude mean
that the designer can use less per-channel inductance and
lower total output capacitance for any performance
specification.
Figure 2 illustrates the multiplicative effect on output ripple
frequency. The three channel currents (IL1, IL2, and IL3),
combine to form the AC ripple current and the DC load
current. The ripple component has three times the ripple
frequency of each individual channel current. Each PWM
pulse is terminated 1/3 of a cycle after the PWM pulse of the
previous phase. The peak-to-peak current waveforms for
each phase is about 7A, and the dc components of the
inductor currents combine to feed the load.
( V IN – V OUT ) V OUT
I L, PP = ----------------------------------------------------L fS V
IN
(EQ. 1)
In Equation 1, VIN and VOUT are the input and output
voltages respectively, L is the single-channel inductor value,
and fS is the switching frequency.
( V IN – N V OUT ) V OUT
I PP = -----------------------------------------------------------L fS V
IN
(EQ. 2)
The output capacitors conduct the ripple component of the
inductor current. In the case of multi-phase converters, the
capacitor current is the sum of the ripple currents from each
of the individual channels. Compare Equation 1 to the
expression for the peak-to-peak current after the summation
of N symmetrically phase-shifted inductor currents in
Equation 2. Peak-to-peak ripple current decreases by an
amount proportional to the number of channels. Output
voltage ripple is a function of capacitance, capacitor
equivalent series resistance (ESR), and inductor ripple
current. Reducing the inductor ripple current allows the
designer to use fewer or less costly output capacitors.
Another benefit of interleaving is to reduce input ripple
current. Input capacitance is determined in part by the
maximum input ripple current. Multi-phase topologies can
improve overall system cost and size by lowering input ripple
current and allowing the designer to reduce the cost of input
capacitance. The example in Figure 3 illustrates input
currents from a three-phase converter combining to reduce
the total input ripple current.
Input-capacitor current, 10A/DIV
IL1 + IL2 + IL3, 7A/DIV
IL3, 7A/DIV
Channel 3
input current
10A/DIV
PWM3, 5V/DIV
IL2, 7A/DIV
PWM2, 5V/DIV
IL1, 7A/DIV
Channel 2
input current
10A/DIV
Channel 1
input current
10A/DIV
PWM1, 5V/DIV
1μs/div
FIGURE 2. PWM AND INDUCTOR-CURRENT WAVEFORMS
FOR 3-PHASE CONVERTER
7
1μs/div
FIGURE 3. CHANNEL INPUT CURRENTS AND INPUTCAPACITOR RMS CURRENT FOR 3-PHASE
FN9093.1
March 20, 2007
ISL6219A
The converter depicted in Figure 3 delivers 36A to a 1.5V
load from a 12V input. The RMS input capacitor current is
5.9A. Compare this to a single-phase converter also down
12V to 1.5V at 36A. The single-phase converter has 11.9A
rms input capacitor current. The single-phase converter
must use an input capacitor bank with twice the RMS current
capacity as the equivalent three-phase converter.
Figures 14 and 15 in the section entitled can be used to
determine the input-capacitor rms current based on load
current, duty cycle, and the number of active channels. They
are provided as aids in determining the optimal input
capacitor solution. Figure 16 shows the single phase inputcapacitor rms current for comparisson.
PWM OPERATION
The number of active channels selected determines the
timing for each channel. By default, the timing mode for the
ISL6219A is 3-phase. The designer can select 2-phase
timing by connecting PWM3 to VCC.
One switching cycle for the ISL6219A is defined as the time
between PWM1 pulse termination signals (the internal signal
that initiates a falling edge on PWM1). The cycle time is the
inverse of the switching frequency selected by the resistor
connected between the FS/EN pin and ground (see
Switching Frequency). Each cycle begins when a clock signal
commands the channel-1 PWM output to go low. This
signals the channel-1 MOSFET driver to turn off the channel1 upper MOSFET and turn on the channel-1 synchronous
MOSFET. If two-channel operation is selected, the PWM2
pulse terminates 1/2 of a cycle later. If three channels are
selected the PWM2 pulse terminates 1/3 of a cycle after
PWM1, and the PWM3 output will follow after another 1/3 of
a cycle.
Once a channel’s PWM pulse terminates, it remains low for
a minimum of 1/4 cycle. This forced off time is required to
assure an accurate current sample as described in Current
Sensing. Following the 1/4-cycle forced off time, the
controller enables the PWM output. Once enabled, the PWM
output transitions high when the sawtooth signal crosses the
adjusted error-amplifier output signal, VCOMP as illustrated
in Figures 1 and 5. This is the signal for the MOSFET driver
to turn off the synchronous MOSFET and turn on the upper
MOSFET. The output will remain high until the clock signals
the beginning of the next cycle by commanding the PWM
pulse to terminate.
CURRENT SENSING
Intersil multi-phase controllers sense current by sampling the
voltage across the lower MOSFET during its conduction
interval. MOSFET rDS(ON) sensing is a no-added-cost
method to sense current for load-line regulation, channelcurrent balance, module current sharing, and overcurrent
protection. If desired, an independent current-sense resistor
in series with the lower-MOSFET source can serve as a
sense element in place of the MOSFET rDS(ON).
8
VIN
In
r DS ( ON )
I
SEN = I L ------------------------R ISEN
CHANNEL N
UPPER MOSFET
IL
SAMPLE
&
HOLD
ISEN(n)
-
RISEN
+
I
+
r
L DS ( ON )
CHANNEL N
LOWER MOSFET
ISL6219A INTERNAL CIRCUIT
EXTERNAL CIRCUIT
FIGURE 4. INTERNAL AND EXTERNAL CURRENT-SENSING
CIRCUITRY
The ISEN input for each channel uses a ground-referenced
amplifier to reproduce a signal proportional to the channel
current (Figure 4). After sufficient settling time, the sensed
current is sampled, and the sample is used for current
balance, load-line regulation and overcurrent protection. The
ISL6219A samples channel current once each cycle.
Figure 4 shows how the sampled current, In, is created from
the channel current IL. The circuitry in Figure 4 represents
the current measurement and sampling circuitry for channel
n in an N-channel converter. This circuitry is repeated for
each channel in the converter but will not be active in
unused channels.
CHANNEL-CURRENT BALANCE
Another benefit of multi-phase operation is the thermal
advantage gained by distributing the dissipated heat over
multiple devices and greater area. By doing this, the
designer avoids the complexity of driving multiple parallel
MOSFETs and the expense of using expensive heat sinks
and exotic magnetic materials.
In order to fully realize the thermal advantage, it is important
that each channel in a multi-phase converter be controlled to
deliver about the same current at any load level. Intersil
multi-phase controllers guarantee current balance by
comparing each channel’s current to the average current
delivered by all channels and making an appropriate
adjustment to each channel’s pulse width based on the error.
Intersil’s patented current-balance method is illustrated in
Figure 5 where the average of the 2 or 3 sampled channel
currents combines with the channel 1 sample, I1, to create
an error signal IER. The filtered error signal modifies the
pulse width commanded by VCOMP to correct any
unbalance and force IER toward zero.
FN9093.1
March 20, 2007
ISL6219A
VCOMP
+
+
-
OUTPUT CURRENT, 20A/DIV
PWM1
SAWTOOTH SIGNAL
f(jω)
I3
IER
IAVG
-
÷N
+
0A
Σ
OUTPUT VOLTAGE,
500mV/DIV
I2
I1
FIGURE 5. CHANNEL-1 PWM FUNCTION AND CURRENTBALANCE ADJUSTMENT
In some circumstances, it may be necessary to deliberately
design some channel-current unbalance into the system. In
a highly compact design, one or two channels may be able
to cool more effectively than the other(s) due to nearby air
flow or heat sinking components. The other channel(s) may
have more difficulty cooling with comparatively less air flow
and heat sinking. The hotter channels may also be located
close to other heat-generating components tending to drive
their temperature even higher. In these cases, a proper
selection of the current sense resistors (RISEN in Figure 4)
introduces channel current unbalance into the system.
Increasing the value of RISEN in the cooler channels and
decreasing it in the hotter channels moves all channels into
thermal balance at the expense of current balance.
0V
5ms/DIV
FIGURE 6. OVERCURRENT BEHAVIOR IN HICCUP MODE
The integrating compensation network shown in Figure 7
assures that the steady-state error in the output voltage is
limited to the error in the reference voltage (output of the
DAC) plus offset errors in the error amplifier. Intersil
specifies the guaranteed tolerance of the ISL6219A to
include all variations in the amplifiers and reference so that
the output voltage remains within the specified system
tolerance.
EXTERNAL CIRCUIT
RC
CC
ISL6219A INTERNAL CIRCUIT
COMP
OVERCURRENT PROTECTION
The average current, IAVG in Figure 5, is continually
compared with a constant 75μA reference current. If the
average current at any time exceeds the reference current,
the comparator triggers the converter to shut down. All PWM
signals are placed in a high-impedance state which signals
the drivers to turn off both upper and lower MOSFETs. The
system remains in this state while the controller counts 2048
phase-clock cycles.
This is followed by a soft-start attempt (see Soft-Start). If the
soft-start attempt is successful, operation will continue as
normal. Should the soft-start attempt fail, the ISL6219A
repeats the 2048-cycle wait period and follows with another
soft-start attempt. This hiccup mode of operation continues
indefinitely as shown in Figure 6 as long as the controller is
enabled or until the overcurrent condition resolves.
ERROR AMPLIFIER
FB
RFB
+
+
VDROOP
IAVG
-
VCOMP
REFERENCE
VOLTAGE(VDAC)
VSEN
VOUT
FIGURE 7. OUTPUT-VOLTAGE AND LOAD-LINE
REGULATION
VOLTAGE REGULATION
The ISL6219A uses a digital to analog converter (DAC) to
generate a reference voltage based on the logic signals at
pins VID4 to VID0. The DAC decodes the a 5-bit logic signal
(VID) into one of the discrete voltages shown in Table 1. Each
VID input offers a 20mA pull up to 2.5V for use with opendrain outputs. External pull-up resistors or active-high outputstages can augment the pull-up current sources, but a slight
accuracy error can occur if they are pulled above 2.9V.
9
FN9093.1
March 20, 2007
ISL6219A
TABLE 1. VOLTAGE IDENTIFICATION CODES
MOSFETs to turn on. The ISL6219A will continue to protect
the load in this fashion as long as the overvoltage repeats.
VID4
VID3
VID2
VID1
VID0
VDAC
1
1
1
1
1
Off
1
1
1
1
0
1.100
1
1
1
0
1
1.125
1
1
1
0
0
1.150
After detecting an overvoltage condition, the ISL6219A
terminates normal PWM operation until it is reset by one of
two methods. Either by pulling VCC below the POR falling
threshold and restoring it above the POR rising threshold or
cycling FS/EN.
1
1
0
1
1
1.175
Under-Voltage
1
1
0
1
0
1.200
1
1
0
0
1
1.225
1
1
0
0
0
1.250
The VSEN pin also detects when the CORE voltage drops
below the VID programmed under-voltage falling threshold.
This causes PGOOD to go low, but has no other effect on
operation and is not latched.
1
0
1
1
1
1.275
1
0
1
1
0
1.300
1
0
1
0
1
1.325
1
0
1
0
0
1.350
1
0
0
1
1
1.375
1
0
0
1
0
1.400
1
0
0
0
1
1.425
1
0
0
0
0
1.450
0
1
1
1
1
1.475
0
1
1
1
0
1.500
0
1
1
0
1
1.525
0
1
1
0
0
1.550
0
1
0
1
1
1.575
0
1
0
1
0
1.600
0
1
0
0
1
1.625
0
1
0
0
0
1.650
0
0
1
1
1
1.675
0
0
1
1
0
1.700
0
0
1
0
1
1.725
0
0
1
0
0
1.750
ENABLE AND DISABLE
0
0
0
1
1
1.775
0
0
0
1
0
1.800
0
0
0
0
1
1.825
Three separate input conditions must be met before the
ISL6219A is released from shut-down mode. The PWM
outputs are held in a high-impedance state to assure the
drivers remain off during shut-down.
0
0
0
0
0
1.850
OVERVOLTAGE PROTECTION
If the ISL6219A detects output voltages above 115% of VID,
the controller will immediately commands all PWM outputs
low. This directs the Intersil drivers to turn on the lower
MOSFETs and protect the load by preventing any further
increase in output voltage. Once the output voltage falls to
the level set by the VID code, the PWM outputs enter highimpedance mode. The Intersil drivers respond by turning off
both upper and lower MOSFETs. If the overvoltage condition
reoccurs, the ISL6219A will again command the lower
10
LOAD-LINE REGULATION
In applications with high transient current slew rates, the
lowest-cost solution for maintaining regulation often requires
some kind of controlled output impedance. A current
proportional to the average current of all active channels is
steered into the inverting input of the error amplifier. There is
no DC return path connected to the FB pin except for the
feedback resistor, RFB. Therefore, the average current,
IAVG, produces a voltage drop across the feedback resistor,
RFB, proportional to the output current. In Figure 7, the
steady-state value of VDROOP is simply
V DROOP = I AVG R FB
(EQ. 3)
In the case that each channel uses the same value for RISEN to
sense channel current, a more complete expression for
VDROOP can be determined from the expression for IAVG as it
is derived from Figures 4 and 5.
I OUT
I AVG = ------------N
r DS ( ON )
---------------------R ISEN
I OUT
V DROOP = ------------N
r DS ( ON )
---------------------- R FB
R ISEN
(EQ. 4)
The internal power-on reset circuit (POR) prevents the
ISL6219A from starting before the bias voltage at VCC
reaches the POR-rising threshold as defined in Electrical
Specifications. The rising threshold is high enough to
guarantee that all parts of the ISL6219A can perform their
functions properly. There is enough hysteresis in the PORfalling threshold to prevent nuisance tripping.
FN9093.1
March 20, 2007
ISL6219A
VCC
1.23V
+
-
+
EXTERNAL CIRCUIT
The soft-start time, tSS, is determined by an 11-bit counter
that increments with every pulse of the phase clock. For
example, a converter switching at 300kHz has a soft-start
time of :
2048
2 11
T SS = ---------- = --------------------- = 6.8ms
300kHz
f SW
FS/EN
S1
ENABLE
SIGNAL
(EQ. 5)
Figure 9 shows the waveforms when the regulator is
operating at 300kHz. Note that the soft-start duration is a
function of the Channel Frequency as explained previously.
DYNAMIC VID
FIGURE 8. EXTERNAL ENABLE SIGNAL CIRCUIT
The frequency select/enable input (FS/EN) has a 1V threshold
which must be exceeded before the internal oscillator begins
running. An external enable signal should be used to control the
gate of an external MOSFET tied to the FS/EN pin, see Figure
8. This MOSFET must pull FS/EN below the 1V threshold to
disable the controller. When enabling the controller, this
external enable circuit must release the FS/EN pin to float to the
designed 1.23V level.
The 11111 VID code is reserved as a signal to the controller
that no load is present. The controller will enter shut-down
mode after receiving this code and will start up upon
receiving any other code.
To enable the controller, VCC must be greater than the POR
threshold; FS/EN must be greater than 1V; and VID cannot
be equal to 11111. Once these conditions are true, the
controller immediately initiates a soft start sequence.
SOFT-START
After the POR function is completed with VCC reaching
4.38V, the soft-start sequence is initiated. Soft-Start, by its
slow rise of CORE voltage from zero, avoids an over-current
condition by slowly charging the output capacitors. This
voltage rise is initiated by an internal DAC that slowly raises
the reference voltage to the error amplifier input. The voltage
rise is controlled by the oscillator frequency and the DAC
within the controller, therefore, the output voltage is
effectively regulated as it rises to the final programmed
CORE voltage value.
For the first 32 PWM switching cycles, the DAC output
remains inhibited and the PWM outputs remain in a
high-impedance state. From the 33rd cycle and for another,
approximately 150 cycles the PWM output remains low,
clamping the lower output MOSFETs to ground. The time
variability is due to the error amplifier, sawtooth generator and
comparators moving into their active regions. After this short
interval, the PWM outputs are enabled and increment the
PWM pulse width from zero duty cycle to operational pulse
width, thus allowing the output voltage to slowly reach the
CORE voltage. The CORE voltage will reach its programmed
value before the 2048 cycles, but the PGOOD output will not
be initiated until the 2048th PWM switching cycle.
11
The ISL6219A is capable of executing on-the-fly
output-voltage changes. At the beginning of the phase-1
switching cycle (defined in the section entitled PWM
Operation), the ISL6219A checks for a change in the VID
code. The VID code is the bit pattern present at pins
VID4-VID0 as outlined in Voltage Regulation. If the new
code remains stable for another full cycle, the ISL6219A
begins incrementing the reference by making 25mV change
every two switching cycles until it reaches the new VID code.
Since the ISL6219A recognizes VID-code changes only at
the beginning of a switching cycle, up to one full cycle may
pass before a VID change registers. This is followed by a
one-cycle wait before the output voltage begins to change.
Thus, the total time required for a VID change, tDV, is
dependent on the switching frequency (fS), the size of the
change (ΔVID), and the time before the next switching cycle
begins. The one-cycle uncertainty in Equation 6 is due to the
possibility that the VID code change may occur up to one full
cycle before being recognized. The time required for a
converter running with fS = 500kHz to make a 1.5V to 1.7V
reference-voltage change is between 30μs and 32μs as
calculated using Equation 6. This example is also illustrated
in Figure 10.
SS Interval
VCOMP, 1V/div
0V
VCORE, 1V/div
0V
FS/EN, 2V/div
0V
PGOOD, 5V/div
0V
1ms/div
FIGURE 9. START-UP OF 3 PHASE SYSTEM OPERATING AT
300kHz
FN9093.1
March 20, 2007
ISL6219A
LOWER MOSFET POWER CALCULATION
01110
The calculation for heat dissipated in the lower MOSFET is
simple, since virtually all of the heat loss in the lower
MOSFET is due to current conducted through the channel
resistance (rDS(ON)). In Equation 7, IM is the maximum
continuous output current; IL,PP is the peak-to-peak inductor
current (see Equation 1); d is the duty cycle (VOUT/VIN); and
L is the per-channel inductance.
VID, 5V/div
00110
VID CHANGE OCCURS
ANYWHERE HERE
VREF, 100mV/div
1.5V
2
I L ,PP
(1 – d)
⎛ I M⎞ 2
-----------------------------(
1
–
d
)
+
P LOW ,1 = r DS ( ON ) ⎜ ----⎟
12
⎝ N⎠
VOUT, 100mV/div
1.5V
An additional term can be added to the lower-MOSFET loss
equation to account for additional loss accrued during the
dead time when inductor current is flowing through the
lower-MOSFET body diode. This term is dependent on the
diode forward voltage at IM, VD(ON); the switching
frequency, fS; and the length of dead times, td1 and td2, at
the beginning and the end of the lower-MOSFET conduction
interval respectively.
5μs/div
FIGURE 10. DYNAMIC-VID WAVEFORMS FOR 500KHz
ISL6219A BASED MULTI-PHASE BUCK
CONVERTER
.
⎞
1 ⎛ 2 ΔV ID
1 ⎛ 2 ΔV ID⎞
----- ⎜ ---------------- – 1⎟ < t DV ≤ ----- ⎜ -----------------⎟
f S ⎝ 0.025
f S ⎝ 0.025 ⎠
⎠
(EQ. 6)
General Design Guide
This design guide is intended to provide a high-level
explanation of the steps necessary to create a multi-phase
power converter. It is assumed that the reader is familiar with
many of the basic skills and techniques referenced below. In
addition to this guide, Intersil provides complete reference
designs that include schematics, bills of materials, and
example board layouts for all common microprocessor
applications.
Power Stages
The first step in designing a multi-phase converter is to
determine the number of phases. This determination
depends heavily on the cost analysis which in turn depends
on system constraints that differ from one design to the next.
Principally, the designer will be concerned with whether
components can be mounted on both sides of the circuit
board; whether through-hole components are permitted on
either side; and the total board space available for powersupply circuitry. Generally speaking, the most economical
solutions will be for each phase to handle between 15 and
20A. All-surface-mount designs will tend toward the lower
end of this current range and, if through-hole MOSFETs can
be used, higher per-phase currents are possible. In cases
where board space is the limiting constraint, current can be
pushed as high as 30A per phase, but these designs require
heat sinks and forced air to cool the MOSFETs.
MOSFETs
The choice of MOSFETs depends on the current each
MOSFET will be required to conduct; the switching frequency;
the capability of the MOSFETs to dissipate heat; and the
availability and nature of heat sinking and air flow.
12
(EQ. 7)
⎛ I M I PP⎞
⎛ IM I ⎞
PP-⎟ t
P LOW , 2 = V D ( ON ) f S ⎜ ----- + ---------⎟ t d1 + ⎜ ----- – -------2 ⎠
2 ⎠ d2
⎝N
⎝N
(EQ. 8)
Thus the total power dissipated in each lower MOSFET is
approximated by the summation of PL and PD.
UPPER MOSFET POWER CALCULATION
In addition to rDS(ON) losses, a large portion of the upperMOSFET losses are due to currents conducted across the
input voltage (VIN) during switching. Since a substantially
higher portion of the upper-MOSFET losses are dependant
on switching frequency, the power calculation is somewhat
more complex. Upper MOSFET losses can be divided into
separate components involving the upper-MOSFET
switching times; the lower-MOSFET body-diode reverserecovery charge, Qrr; and the upper MOSFET rDS(ON)
conduction loss.
When the upper MOSFET turns off, the lower MOSFET does
not conduct any portion of the inductor current until the
voltage at the phase node falls below ground. Once the
lower MOSFET begins conducting, the current in the upper
MOSFET falls to zero as the current in the lower MOSFET
ramps up to assume the full inductor current. In Equation 9,
the required time for this commutation is t1and the
associated power loss is PUP,1.
⎛ I M I L ,PP⎞ ⎛ t 1 ⎞
P UP,1 ≈ V IN ⎜ ----- + -------------⎟ ⎜ ---- ⎟ f S
2 ⎠⎝ 2⎠
⎝N
(EQ. 9)
Similarly, the upper MOSFET begins conducting as soon as
it begins turning on. In Equation 10, this transition occurs
over a time t2, and the approximate the power loss is PUP,2.
FN9093.1
March 20, 2007
ISL6219A
.
ΔT 2
R ISEN ,2 = R ISEN ---------ΔT 1
⎛ I M I L ,PP⎞ ⎛ t 2 ⎞
P UP, 2 ≈ V IN ⎜ ----- – -------------⎟ ⎜ ---- ⎟ f S
2 ⎠⎝ 2⎠
⎝N
(EQ. 10)
A third component involves the lower MOSFET’s reverserecovery charge, Qrr. Since the inductor current has fully
commutated to the upper MOSFET before the lowerMOSFET’s body diode can recover all of Qrr, it is conducted
through the upper MOSFET across VIN. The power
dissipated as a result is PUP,3 and is simply:
P UP,3 = V IN Q rr f S
(EQ. 11)
Finally, the resistive part of the upper MOSFET’s is given in
Equation 12 as PUP,4.
2
I PP2
⎛ I M⎞
P UP,4 = r DS ( ON ) ⎜ -----⎟ d + ---------12
⎝ N⎠
(EQ. 12)
In this case, of course, rDS(ON) is the on resistance of the
upper MOSFET.
The total power dissipated by the upper MOSFET at full load
can now be approximated as the summation of the results
from Equations 9, 10, 11 and 12. Since the power equations
depend on MOSFET parameters, choosing the correct
MOSFETs can be an iterative process that involves
repetitively solving the loss equations for different MOSFETs
and different switching frequencies until converging upon the
best solution.
Current Sensing
Pins 23, 20 and 19 are the ISEN pins denoted ISEN1, ISEN2
and ISEN3, respectively. The resistors connected between
these pins and the phase nodes determine the gains in the
load-line regulation loop and the channel-current balance
loop. Select the values for these resistors based on the room
temperature rDS(ON) of the lower MOSFETs; the full-load
operating current, IFL; and the number of phases, N
according to Equation 13 (see also Figure 4).
.
r DS ( ON ) I FL
- -------R ISEN = ---------------------50 ×10 – 6 N
(EQ. 13)
In certain circumstances, it may be necessary to adjust the
value of one or more of the ISEN resistors. This can arise
when the components of one or more channels are inhibited
from dissipating their heat so that the affected channels run
hotter than desired (see the section entitled Channel-Current
Balance). In these cases, chose new, smaller values of RISEN
for the affected phases. Choose RISEN,2 in proportion to the
desired decrease in temperature rise in order to cause
proportionally less current to flow in the hotter phase.
13
(EQ. 14)
In Equation 14, make sure that ΔT2 is the desired temperature
rise above the ambient temperature, and ΔT1 is the measured
temperature rise above the ambient temperature. While a
single adjustment according to Equation 14 is usually
sufficient, it may occasionally be necessary to adjust RISEN
two or more times to achieve perfect thermal balance
between all channels.
Load-Line Regulation Resistor
The load-line regulation resistor is labeled RFB in Figure 7.
Its value depends on the desired full-load droop voltage
(VDROOP in Figure 7). If Equation 13 is used to select each
ISEN resistor, the load-line regulation resistor is as shown
in Equation 15.
V DROOP
R FB = ------------------------–6
50 ×10
(EQ. 15)
If one or more of the ISEN resistors was adjusted for thermal
balance as in Equation 14, the load-line regulation resistor
should be selected according to Equation16 where IFL is the
full-load operating current and RISEN(n) is the ISEN resistor
connected to the nth ISEN pin.
V DROOP
R FB = -------------------------------I FL r DS ( ON )
∑ RISEN ( n )
n
(EQ. 16)
Compensation
The two opposing goals of compensating the voltage
regulator are stability and speed. Depending on whether the
regulator employs the optional load-line regulation as
described in Load-Line Regulation, there are two distinct
methods for achieving these goals.
COMPENSATING A LOAD-LINE REGULATED
CONVERTER
The load-line regulated converter behaves in a similar
manner to a peak-current mode controller because the two
poles at the output-filter L-C resonant frequency split with
the introduction of current information into the control loop.
The final location of these poles is determined by the system
function, the gain of the current signal, and the value of the
compensation components, RC and CC.
Since the system poles and zero are effected by the values
of the components that are meant to compensate them, the
solution to the system equation becomes fairly complicated.
Fortunately there is a simple approximation that comes very
close to an optimal solution. Treating the system as though it
were a voltage-mode regulator by compensating the L-C
poles and the ESR zero of the voltage-mode approximation
yields a solution that is always stable with very close to ideal
transient performance.
FN9093.1
March 20, 2007
ISL6219A
Once selected, the compensation values in Equations 17
assure a stable converter with reasonable transient performance. In most cases, transient performance can be
improved by making adjustments to RC. Slowly increase the
value of RC while observing the transient performance on an
oscilloscope until no further improvement is noted. Normally,
CC will not need adjustment. Keep the value of CC from
Equations 17 unless some performance issue is noted.
C2 (OPTIONAL)
CC
COMP
FB
+
RFB
VDROOP
ISL6219A
RC
The optional capacitor C2, is sometimes needed to bypass
noise away from the PWM comparator (see Figure 5). Keep
a position available for C2, and be prepared to install a highfrequency capacitor of between 22pF and 150pF in case any
jitter problem is noted.
VSEN
COMPENSATION WITHOUT LOAD-LINE REGULATION
FIGURE 11. COMPENSATION CONFIGURATION FOR
LOAD-LINE REGULATED ISL6219A CIRCUIT
The feedback resistor, RFB, has already been chosen as outlined in Load-Line Regulation Resistor. Select a target bandwidth for the compensated system, f0. The target bandwidth
must be large enough to assure adequate transient performance, but smaller than 1/3 of the per-channel switching frequency. The values of the compensation components
depend on the relationships of f0 to the L-C pole frequency
and the ESR zero frequency. For each of the three cases
defined in the following, there is a separate set of equations
for the compensation components
.
1
------------------- > f 0
2π LC
In the solutions to the compensation equations, there is a single degree of freedom. For the solutions presented in Equations 18, RFB is selected arbitrarily. The remaining
compensation components are then selected according to
Equation 18.
2πf 0 V pp LC
R C = R FB -----------------------------------0.75V
IN
0.75V IN
C C = -----------------------------------2πV PP R FB f 0
Case 2:
The first step is to choose the desired bandwidth, f0, of the
compensated system. Choose a frequency high enough to
assure adequate transient performance but not higher than
1/3 of the switching frequency. The type-III compensator has
an extra high-frequency pole, fHF. This pole can be used for
added noise rejection or to assure adequate attenuation at
the error-amplifier high-order pole and zero frequencies. A
good general rule is to chose fHF = 10 f0, but it can be higher
if desired. Choosing fHF to be lower than 10 f0 can cause
problems with too much phase shift below the system bandwidth.
1
1
------------------- ≤ f 0 < -----------------------------2πC ( ESR )
2π LC
V PP ( 2π ) 2 f 02 LC
R C = R FB -------------------------------------------0.75 V
C2
(EQ. 17)
RC
IN
0.75V IN
C C = ------------------------------------------------------------2
( 2π ) f 02 V PP R FB LC
Case 3:
CC
COMP
FB
1
f 0 > -----------------------------2πC ( ESR )
C1
2π f 0 V pp L
R C = R FB -----------------------------------------0.75 V IN ( ESR )
R1
+
RFB
VDROOP
ISL6219A
Case 1:
The non load-line regulated converter is accurately modeled
as a voltage-mode regulator with two poles at the L-C
resonant frequency and a zero at the ESR frequency. A type
III controller, as shown in Figure 12, provides the necessary
compensation.
-
VSEN
0.75V IN ( ESR ) C
C C = ------------------------------------------------2πV PP R FB f 0 L
In Equations 17, L is the per-channel filter inductance divided
by the number of active channels; C is the sum total of all output capacitors; ESR is the equivalent-series resistance of the
bulk output-filter capacitance; and VPP is the peak-to-peak
sawtooth signal amplitude as described in Figure 5 and
Electrical Specifications on page 5.
14
FIGURE 12. COMPENSATION CIRCUIT FOR ISL6219A BASED
CONVERTER WITHOUT LOAD-LINE
REGULATION.
FN9093.1
March 20, 2007
ISL6219A
Neglecting the contribution of inductor current and regulator
response, the output voltage initially deviates by an amount:
.
LC – C ( ESR )
C 1 = ----------------------------------------R FB
di
ΔV ≈ ( ESL ) ----- + ( ESR ) ΔI
dt
2
V PP ⎛ 2π⎞ f 0 f HF LC
⎝ ⎠
R C = --------------------------------------------------------------------0.75 V IN 2π f HF ⎛⎝ LC – 1⎞⎠
The filter capacitor must have sufficiently low ESL and ESR
so that ΔV < ΔVMAX.
C ( ESR )
R 1 = R FB ----------------------------------------LC – C ( ESR )
Most capacitor solutions rely on a mixture of high-frequency
capacitors with relatively low capacitance in combination
with bulk capacitors having high capacitance but limited
high-frequency performance. Minimizing the ESL of the
high-frequency capacitors allows them to support the output
voltage as the current increases. Minimizing the ESR of the
bulk capacitors allows them to supply the increased current
with less output voltage deviation.
0.75V IN
C 2 = ------------------------------------------------------------------2
( 2π ) f 0 f HF LCR FB V PP
0.75V IN
C C = ---------------------------------------------------------------------------------⎛
⎞
1
2πV PP R f 0 ⎜ 1 – -----------------------------⎟
FB ⎜
2πf HF LC⎟⎠
⎝
(EQ. 18)
In Equation 18, L is the per-channel filter inductance divided
by the number of active channels; C is the sum total of all
output capacitors; ESR is the equivalent-series resistance of
the bulk output-filter capacitance; and VPP is the peak-topeak sawtooth signal amplitude as described in Figure 5 and
Electrical Specifications on page 5.
OUTPUT FILTER DESIGN
The output inductors and the output capacitor bank together
form a low-pass filter responsible for smoothing the pulsating
voltage at the phase nodes. The output filter also must
provide the transient energy during the interval of time after
the beginning of the transient until the regulator can fully
respond. Because it has a low bandwidth compared to the
switching frequency, the output filter necessarily limits the
system transient response leaving the output capacitor bank
to supply or sink load current while the current in the output
inductors increases or decreases to meet the demand.
In high-speed converters, the output capacitor bank is
usually the most costly (and often the largest) part of the
circuit. Output filter design begins with minimizing the cost of
this part of the circuit. The critical load parameters in
choosing the output capacitors are the maximum size of the
load step, ΔI; the load-current slew rate, di/dt; and the
maximum allowable output-voltage deviation under transient
loading, ΔVMAX. Capacitors are characterized according to
their capacitance, ESR, and ESL (equivalent series
inductance).
At the beginning of the load transient, the output capacitors
supply all of the transient current. The output voltage will
initially deviate by an amount approximated by the voltage
drop across the ESL. As the load current increases, the
voltage drop across the ESR increases linearly until the load
current reaches its final value. The capacitors selected must
have sufficiently low ESL and ESR so that the total output
voltage deviation is less than the allowable maximum.
15
(EQ. 19)
The ESR of the bulk capacitors also creates the majority of
the output-voltage ripple. As the bulk capacitors sink and
source the inductor ac ripple current (see Interleaving and
Equation 2), a voltage develops across the bulk-capacitor
ESR equal to IPP (ESR). Thus, once the output capacitors
are selected, the maximum allowable ripple voltage,
VPP(MAX), determines the a lower limit on the inductance.
⎛V – N V
⎞
OUT⎠ V OUT
⎝ IN
L ≥ ( ESR ) -----------------------------------------------------------f S V IN V PP( MAX )
(EQ. 20)
Since the capacitors are supplying a decreasing portion of
the load current while the regulator recovers from the
transient, the capacitor voltage becomes slightly depleted.
The output inductors must be capable of assuming the entire
load current before the output voltage decreases more than
ΔVMAX. This places an upper limits on inductance.
2NCVO
L ≤ --------------------- ΔV MAX – ΔI ( ESR )
( ΔI ) 2
( 1.25 ) NC
L ≤ -------------------------- ΔV MAX – ΔI ( ESR ) ⎛ V IN – V O⎞
⎝
⎠
( ΔI ) 2
(EQ. 21)
(EQ. 22)
Equation 22 gives the upper limit on L for the cases when the
trailing edge of the current transient causes a greater outputvoltage deviation than the leading edge. Equation 21
addresses the leading edge. Normally, the trailing edge dictates
the selection of L because duty cycles are usually less than
50%. Nevertheless, both inequalities should be evaluated, and
L should be selected based on the lower of the two results. In
each equation, L is the per-channel inductance, C is the total
output capacitance, and N is the number of active channels.
FN9093.1
March 20, 2007
ISL6219A
Switching Frequency
[11.09 – 1.13 log ( f S ) ]
(EQ. 23)
Figures 14 and 15 can be used to determine the input-capacitor
rms current as of duty cycle, maximum sustained output current
(IO), and the ratio of the combined peak-to-peak inductor
current (IL,PP) to IO. Figure 16 is provided as a reference to
demonstrate the dramatic reductions in input-capacitor rms
current upon the implementation of the multiphase topology.
Input Capacitor Selection
The input capacitors are responsible for sourcing the ac
component of the input current flowing into the upper
MOSFETs. Their rms current capacity must be sufficient to
handle the ac component of the current drawn by the upper
MOSFETs which is related to duty cycle and the number of
active phases.
Figures 14 and 15 can be used to determine the input-capacitor
RMS current as of duty cycle, maximum sustained output
current (IO), and the ratio of the combined peak-to-peak
inductor current (IL,PP) to IO. Figure 16 is provided as a
reference to demonstrate the dramatic reductions in inputcapacitor rms current upon the implementation of the
multiphase topology.
0.2
0.1
IPP = 0
IPP = 0.5 IO
IPP = 0.75 IO
0
0
0.2
0.4
0.6
0.8
1.0
DUTY CYCLE (VO /VIN)
FIGURE 14. NORMALIZED INPUT-CAPACITOR RMS
CURRENT VS DUTY CYCLE FOR 2-PHASE
CONVERTER
0.3
INPUT-CAPACITOR CURRENT (IRMS / IO)
RT = 10
INPUT-CAPACITOR CURRENT (IRMS / IO)
0.3
There are a number of variables to consider when choosing the
switching frequency. There are considerable effects on the
upper-MOSFET loss calculation and, to a lesser extent, the
lower-MOSFET loss calculation. These effects are outlined in
MOSFETs, and they establish the upper limit for the switching
frequency. The lower limit is established by the requirement for
fast transient response and small output-voltage ripple as
outlined in Output Filter Design. Choose the lowest switching
frequency that allows the regulator to meet the transientresponse requirements. Switching frequency is determined by
the selection of the frequency-setting resistor, RT (see the
figure Typical Application on page 3). Figure 13 and Equation
23 are provided to assist in the selecting the correct value for
RT.
IPP = 0
IPP = 0.5 IO
IPP = 0.25 IO
IPP = 0.75 IO
0.2
0.1
0
0
0.2
0.4
0.6
0.8
1.0
DUTY CYCLE (VIN / VO)
FIGURE 15. NORMALIZED INPUT-CAPACITOR RMS
CURRENT VS DUTY CYCLE FOR 3-PHASE
0.6
INPUT-CAPACITOR CURRENT (IRMS / IO)
RT (kΩ)
1000
100
0.4
0.2
IPP = 0
IPP = 0.5 IO
IPP = 0.75 IO
0
10
10
100
1000
SWITCHING FREQUENCY (KHZ)
FIGURE 13. RT VS SWITCHING FREQUENCY
16
10000
0
0.2
0.4
0.6
DUTY CYCLE (VIN / VO)
0.8
1.0
FIGURE 16. NORMALIZED INPUT-CAPACITOR RMS
CURRENT VS DUTY CYCLE FOR SINGLE-PHASE
CONVERTER
FN9093.1
March 20, 2007
ISL6219A
Shrink Small Outline Plastic Packages (SSOP)
Quarter Size Outline Plastic Packages (QSOP)
M28.15
N
INDEX
AREA
H
0.25(0.010) M
28 LEAD SHRINK SMALL OUTLINE PLASTIC PACKAGE
(0.150” WIDE BODY)
B M
E
1
2
INCHES
GAUGE
PLANE
-B-
SYMBOL
3
L
0.25
0.010
SEATING PLANE
-A-
A
D
h x 45°
-C-
α
e
A2
A1
B
C
0.10(0.004)
0.17(0.007) M
C A M
B S
NOTES:
1. Symbols are defined in the “MO Series Symbol List” in Section 2.2
of Publication Number 95.
2. Dimensioning and tolerancing per ANSI Y14.5M-1982.
MIN
MAX
MILLIMETERS
MIN
MAX
NOTES
A
0.053
0.069
1.35
1.75
-
A1
0.004
0.010
0.10
0.25
-
A2
-
0.061
-
1.54
-
B
0.008
0.012
0.20
0.30
9
C
0.007
0.010
0.18
0.25
-
D
0.386
0.394
9.81
10.00
3
E
0.150
0.157
3.81
3.98
4
e
0.025 BSC
0.635 BSC
-
H
0.228
0.244
5.80
6.19
-
h
0.0099
0.0196
0.26
0.49
5
L
0.016
0.050
0.41
1.27
6
N
α
28
0°
28
8°
0°
7
8°
3. Dimension “D” does not include mold flash, protrusions or gate
burrs. Mold flash, protrusion and gate burrs shall not exceed
0.15mm (0.006 inch) per side.
Rev. 1 6/04
4. Dimension “E” does not include interlead flash or protrusions. Interlead flash and protrusions shall not exceed 0.25mm (0.010 inch)
per side.
5. The chamfer on the body is optional. If it is not present, a visual index feature must be located within the crosshatched area.
6. “L” is the length of terminal for soldering to a substrate.
7. “N” is the number of terminal positions.
8. Terminal numbers are shown for reference only.
9. Dimension “B” does not include dambar protrusion. Allowable dambar protrusion shall be 0.10mm (0.004 inch) total in excess of “B”
dimension at maximum material condition.
10. Controlling dimension: INCHES. Converted millimeter dimensions
are not necessarily exact.
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
17
FN9093.1
March 20, 2007
Similar pages