an1132

ISL6559EVAL1: Voltage Regulator Module
Solution for AMD Hammer Family Processors
®
Application Note
June 2004
AN1132
Author: Thomas Victorin
Introduction
ISL6559 VRM Reference Design
The AMD Hammer family microprocessors feature higher
clock speeds and greater device density than previous
product families. The power management solution for this
next generation family of microprocessors must contend with
lower core voltages, tighter transient specifications, and
higher peak current demands. Responding to the changing
power management needs of its customers, Intersil
introduces the ISL6559 controller to power the AMD
Hammer family microprocessors.
The evaluation kit consists of the ISL6559EVAL1 board,
associated data sheets on the ISL6559 controller and
ISL6605 driver, as well as this application note. The
evaluation kit also includes the Elcon VRM test board which
has an edged connector for the VRM to plug into. The
evaluation kit provides convenient test points, a banana jack
for power supply connectors, and an on-board transient load
generator to facilitate the evaluation process. The
ISL6559EVAL1 board and test board is configured to run off
of a single 12V supply.
Intersil ISL6559 and ISL6605
The ISL6559EVAL1 is a versatile voltage regulator-module
(VRM) design. The evaluation board comes configured for
4-phase multi-phase buck operation, designed to meet AMD
Hammer Family Desktop Processor specifications. The
board can easily be modified to support evaluation at lower
current specifications. The ISL6559 controller functions are
specifically designed to compliment and support the
Hammer Family feature set with ISL6605 drivers. The
chipset forms a highly integrated solution for AMD Hammer
processor applications.
The ISL6559 regulates output voltage and balances load
currents for two to four synchronous buck converter
channels. The controller features a 5-bit DAC, which
provides a digital interface for accurate voltage programming
over the entire Hammer Family range of 0.800V to 1.550V.
New multi-phase family features include differential remote
output voltage sensing, to improve regulation tolerance;
pin-adjustable reference offset, for ease of implementation;
VID-on-the-Fly, to respond to DAC changes during
operation; and optional load line regulation. For a more
detailed description of the ISL6559 functionality, refer to the
data sheet [1].
The ISL6605 driver is chosen to drive two N-Channel power
MOSFETs in a synchronous-rectified buck converter
channel. Each channel has a single logic input that controls
the upper and lower MOSFETs. Dead time is optimized on
both switching edges to provide shoot-thru protection.
Internal bootstrap circuitry only requires an external
capacitor and provides better enhancement of the upper
MOSFET. For a more detailed description of the ISL6605,
refer to the data sheet [2].
The Intersil multi-phase family controller and driver portfolio
continues to expand with new selections to better fit our
customer’s needs. Refer to our website for updated
information, www.intersil.com.
1
TABLE 1. 4-PHASE VRM DESIGN PARAMETERS
PARAMETER
MIN
MAX
Static Regulation
1.109V
1.250V
Transient Regulation
1.109V
1.250V
3A
100A
Continuous Load Current
Load Current Step
Load Current Transient
100A
~560A/µs
The evaluation board meets the output voltage and current
specifications, shown in Table 1, with the VID DIP switch (set
to 01100 (1.250V). The 1U VRM board is fabricated using 6
layers with 3oz copper on outer and 4oz copper on inner
layers. The test board is implemented in 4-layer, 2oz copper.
Layout plots and part lists are provided at the end of the
application note for this design.
Quick Start Evaluation
Circuit Setup
The ISL6559EVAL1 board will arrive with the VID DIP switch
(U2) set to 01100 (1.250V). If another output voltage level is
desired, refer to the ISL6559 data sheet for the complete
DAC table and change the VID switches accordingly. Note
that changing the U2 VID states will change the dynamics of
the load generator.
Input Power Connections
A single power supply connection is provided on the VRM
test board. Insure connection is secure.
Two female banana jacks are provided for connection of the
bench top power supply. Connect the +12V terminal to J5,
and the common ground to terminal J6.
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Copyright © Intersil Americas Inc. 2004. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
Application Note 1132
Power Output Connections
900
The ISL6559EVAL1 output can be exercised using either
resistive or electronic loads. Copper alloy terminal lugs
provide connection points for loading. Tie the positive load
connection to VCORE, terminal J2 or J3, and the negative to
ground, terminal J4 and J10. A shielded scope probe test
point, J8, allows for inspection of the output voltage,
VCORE.
800
LOAD di/dt (A/µs)
700
Enabling the Controller
The state of VCC, EN, and FS/DIS dictate the beginning of a
soft-start interval. The FS/DIS pin is used to set the per
phase switching frequency on the evaluation board. Once
the input and output terminal connections are made, remove
the shunt across the jumper (J11) pins 3, 4 labeled OUT_EN
if installed. The EN signal is released to rise above the
ENABLE threshold of 1.23V nominal. Once the ENABLE
threshold is exceeded, a soft-start interval is initiated. The
output voltage will ramp in a controlled manner.
A resistor divider from the +12V input is connected to EN on
the controller and the drivers to insure that the drivers and
controller come up at the same time.
On-Board Load Transient Generator
Most bench-top electronic loads are not capable of
producing the current slew rates required to emulate modern
microprocessors. For this reason, a discrete transient load
generator is provided on the VRM test board for evaluation.
The VRM test board is designed to work in conjunction with
the ISL6559 eval board. The VRM test board schematic is
located in later pages of this application note. In addition to
the transient load generator, the board consists of a card
edge connector (J1), pull up resistors for the VID pins, and
scope probes as well as turrets for monitoring the input and
output voltage. This board comes configured with an all
ceramic output filter, but you have the option to add Oscon
or larger ceramic capacitors.
The on board transient circuit can be modified to operate at
different frequencies or have different load steps. As
received the on-board transient is designed to operate at
33Hz. The current step is dependent on the di/dt of the
transient load which is dependent on the output voltage and
the number of switches being used as seen in Figure 1.
Where:
(EQ. 1)
• di/dt = Vout x N/ (trise x REQ)
• di/dt is the transient slew rate
• N is the number of switches
• trise is the rise time
• REQ is the equivalent resistance
• VOUT is the output voltage
2
600
N=4
500
N=3
400
N=2
300
200
N=1
100
0
0.80
0.90
1.00
1.10
1.20
1.30
1.40
1.50
1.60
VOUT (V)
FIGURE 1. PLOT OF TRANSIENT LOAD CIRCUIT
The load step can be verified by measuring the voltage at J7
of the test board. Once you have that value you can
calculate your current step. The di/dt can be verified by
measuring the rise time of the load step. Rise time is
measured from 10% and 90% of the transient voltage. Plug
that value into equation 1 to calculate the di/dt. The rise time
can be improved by switching to thin film resistors from the
wire wound resistors.
The low frequency transient is running at 33Hz but can be
modified to run faster by simply adjusting the values of R6,
R7 and C80. Frequency can be increased by decreasing the
value of C80 (currently 10µF). If you want to change the duty
cycle, ON time is proportional to R7 (402Ω) and the OFF
time is proportional to R6 (46.7kΩ). It may be necessary to
decrease the ON time at high frequency. If the duty cycle is
too high, the switching transistor and sense resistors will
overheat. Do not use less than 10Ω for R7 or the max pulsed
current in Q1 will exceed its rating.
The load resistor values are 120mΩ stacked 3 high that
gives effectively 40mΩ, the rDS(ON) of the FETs is 16mΩ.
Thus, the equivalent resistance for each switch is 56mΩ.
.
Application Note 1132
ISL6559 VRM Performance
current of the converter and effectively creates an output
voltage droop; the output impedance is 0.91mΩ.
Soft-Start Interval
The typical start-up waveforms for the ISL6559EVAL1 are
shown in Figure 2. The DAC is set to 01100 (1.250V) and the
converter is started into a 100A load. The OUT_EN jumper is
removed and the voltage on EN quickly rises above the
ISL6559 enable threshold, triggering a soft-start interval. The
switching frequency of the converter is 600kHz, therefore the
soft-start interval (SS Interval) is approximately 3.4ms per
the datasheet. On this evaluation board the 5V linear supply
that is used to power up the controller is disabled when the
enable pin is tied low. This causes the PGOOD pin to float
high until VCC rises above the POR threshold of the
controller and pulls the PGOOD pin low.
The rising edge transient response of the ISL6559EVAL1 to
the aforementioned maximum load conditions is shown in
Figure 3. A bench-top electronic load draws 0A continuously
from the converter, while the on-board load generator
provides a ~100A load step. This design incorporates an all
ceramic output filter which reduces the effective ESR/ESL
resulting in an excellent transient response with a measured
bandwidth of 140kHz.
The output undervoltage threshold is defined as the DAC
setting minus 350mV. Once this threshold is surpassed, the
internal pull down on the PGOOD pin is released.
VOUT
PGOOD
FIGURE 3. RISING EDGE TRANSIENT RESPONSE
ENABLE
Figure 4 shows the load release response of the converter.
There is no overshoot due to the low ESR and ESL of the all
ceramic output capacitor bank and small output inductors
(100nH) employed in this design.
FIGURE 2. SOFT-START INTERVAL WAVEFORMS
Transient Response
The transient slew rate is designed for a nominal 560A/µs,
but can be adjusted as described previously. During a
transient, the core voltage is required to remain within the
static window of ±50mV around the DAC setting. The
on-board load generator and a bench-top electronic load
simulate these conditions.
The OFS pin allows the user to positively offset the DAC
reference voltage by placing a correctly sized resistor from
this pin to ground, R14. For this design, the resistor value is
0Ω, which equates to no offset at no-load. Load-line
regulation is supported by the ISL6559. The average current
of the four active channels flows out IOUT. When this pin is
connected to FB, this average current creates a voltage drop
across R9. This voltage drop is proportional to the output
3
FIGURE 4. FALLING EDGE TRANSIENT RESPONSE
Application Note 1132
Overcurrent Protection
VID on the Fly
The ISL6559 monitors the output current level by averaging
the sampled current from each ISEN pin. The RISEN
resistors (R1, R2, R3, R4) are selected such that the current
sourced by the ISEN pins is 50µA at maximum load current.
The average of the sampled currents is compared with an
overcurrent trip level of 90µA. Once the average current
meets or exceeds the OC reference current, the controller
immediately places all PWM signals in a high-impedance
state, quickly removing gate drive to the ISL6605 drivers.
This forces the core voltage to decay as the output
capacitors discharge. The PGOOD signal transitions low
when the core voltage drops below the UV threshold.
The AMD Hammer Family microprocessors can change VID
inputs at any time while the regulator is in operation. The
power management solution is required to monitor the DAC
inputs and respond to VID voltage transitions in a controlled
manner, supervising the safe output voltage transition within
the DAC range of the processor without discontinuity or
disruption. The ISL6559 checks the five VID inputs at the
beginning of each switching cycle. If the VID code has
changed, the controller waits one complete switching cycle
to validate the new code. If the new code is stable during this
one cycle delay, then the controller begins incrementing the
reference voltage toward the new DAC code in 25mV steps,
every two switching-cycles, until the new DAC code is
reached.
After the overcurrent event is detected, the controller waits a
short delay time before initiating a soft-start interval to allow
the disturbance to clear. The delay time is equivalent to the
soft-start interval and for this design is 3.4ms. If during the
soft-start interval another overcurrent trip is detected, the
PWM signals are again placed in a high impedance state
and PGOOD remains low. The controller waits another
3.4ms before another soft-start interval is attempted. This
hiccup mode of operation repeats up to six times, with a
seventh successive event causing the converter to latch off.
Figure 5 shows the hiccup mode operation of the converter
when a hard short is applied across the output terminals of
the evaluation board. The converter quickly places the PWM
signals in a high-impedance state and the core voltage
decays quickly. The short is not removed, resulting in the
controller latching off after the seventh attempt. The hiccup
mode is explained more thoroughly in the datasheet.
1.0V
FIGURE 6. VID-ON-THE-FLY TRANSITION FROM 1.55V TO
1.30V
VCORE, 1V/DIV
LOAD CURRENT, 20A/DIV
0A
PWM1, 10V/DIV
0V
PWM2, 10V/DIV
0V
PWM3, 10V/DIV
0V
10ms/DIV
FIGURE 5. OVERCURRENT PROTECTION
4
Figure 6 shows a 250mV DAC change prompted by
changing VID3 and VID1 simultaneously. Originally at
1.550V (00000), the core voltage ramps to the new DAC
setting of 1.300V (01010). The VID-on-the-Fly transition is
completed in 30µs, well within the 100µs maximum window
allowed. The converter is supporting a 26A load during the
transition. The cursors on the scope shot reflect only a
230mV transition because the transition happened very fast
and the final voltage was not captured.
Figure 7 shows the converter returning to a DAC level of
1.550V after the VID3 and VID1 states are returned to
ground. Again, the converter is loaded at 26A during the
DAC change.
Application Note 1132
cost is reduced thermal and efficiency performance of the
solution. Select an upper MOSFET with an rDS(ON) no larger
than 12mΩ and keep the total gate charge below 15nC. This
combined with a lower MOSFET of no more than 7mΩ with a
total gate charge of 50nC to 70nC can provide a cost
effective and thermally acceptable solution.
Summary
The ISL6559EVAL1 is an adaptable evaluation tool which
showcases the performance of the ISL6559 and ISL6605
chip set. Designed to meet the performance requirements of
AMD’s Hammer Family Desktop microprocessors, the board
allows the user the flexibility to configure the board for
current as well as future microprocessor offerings. The
following pages provide a schematic of the board, bill of
materials and layout drawings to support implementation of
this solution.
FIGURE 7. VID-ON-THE-FLY TRANSITION FROM 1.30V TO
1.55V
Intersil documents are available on the web at
http://www.intersil.com/.
Efficiency
The efficiency of the ISL6559EVAL1 board, loaded up to
100A is plotted in Figure 8. Measurements were performed
at room temperature and taken at thermal equilibrium with
400 LFM of air and heatsink. The design exceeds the AMD
Hammer Desktop minimum requirements of 50% efficiency
under minimum loading and 80% efficiency at maximum
loading.
Additional testing was performed in a wind tunnel where we
were able to achieve a 120A constant load at 45°C ambient
and 300LFM of airflow. The board temperature was
monitored and stabilized at around 100°C.
.
90
85
1.25V
EFFICIENCY (%)
80
75
70
65
60
55
50
0
References
10
20
30
40
50
60
70
80
90
100
LOAD (I)
FIGURE 8. VRM EFFICIENCY vs LOAD CURRENT
Adapting Circuit Performance
Higher rDS(ON) MOSFETs can be employed in the design, if
the cost curve must be tilted lower. The tradeoff for lowering
5
[1] ISL6559 Data Sheet, Intersil Corporation, File No.
FN9084.
[2] ISL6605 Data Sheet, Intersil Corporation, File No.
FN9091.
Schematic
6
Application Note 1132
Application Note 1132
ISL6559EVAL1 Layout
FIGURE 9. TOP
FIGURE 10. BOTTOM
7
VRM Test Board Schematic
8
Application Note 1132
VRM Test Board Schematic
9
Application Note 1132
Application Note 1132
Bill of Materials
QTY
REFERENCE
1
C22
6
1
5
4
C1-C4, C17, C24
C21
C19, C25-C28
C5-C8
COMPONENT
DESCRIPTION/COMMENT
MFG NAME
H1044-00103-25V8020-T Capacitor, SMD, 0402, 0.01µF, 25V, Panasonic
+80-20%, Y5V
Venkel
H1045-00105-16V20-T
H1045-00151-50V5-T
H1045-00222-50V10-T
H1045-00224-10V10-T
C23
1
C20
8
C9-C16
4
H1045-00332-50V10-T
L1-L4
FP4-100
C0402Y5V250-103ZNE
Murata
GRM188R61C105KA12D
Venkel
C0603Y5V160-105MNE
Capacitor, SMD, 0603, 150pF, 50V,
5%, NPO
Panasonic
ECJ-1VC1H151J
Venkel
C0603C0G500-151JNE
Capacitor, SMD, 0603, 2200pF, 50V, Panasonic
10%, X7R
Samsung
CL10B222KBNC
C1608X7R1H222K
Venkel
C0603X7R500-222KNE
Capacitor, SMD, 0603, 3300pF, 50V, BC Components
10%, X7R
Venkel
Capacitor, SMD, 1210, 22µF, 16V,
20%, X5R
ECJ-1VB1H222K
TDK
Capacitor, SMD, 0603, 0.22µF, 10V, AVX
10%, X7R
TDK
H1046-00106-6R3V10-T Capacitor, SMD, 0805, 10µF, 6.3V,
10%, X5R
H1082-00226-16V20-T
ECJ-0EF1E103Z
Capacitor, SMD, 0603, 1µF, 16V,
20%, Y5V
Venkel
1
MFG NUMBER
0603YC224KAT2A
C1608X7R1C224K
C0603X7R100-224KNE
0603B332K500BT
C0603X7R500-332KNE
Venkel
C0805X5R6R3-106KNE
AVX
1210YD226MAT2A
Murata
GRM32ER61C226ME20L
Taiyo Yuden
EMK325BJ226MM (X7R)
TDK
C3225X5R1C226M
Venkel
C1210X5R160-226MNE
Coil-Pwr Inductor, SMD, 10X6.8mm, Cooper Bussmann
FP4-100
0.1µH, 64A
Cooper Electronic Tech. FP4-100
BI Technologies
HM00-03852
1
L5
PM1210-150J
Coil-Inductor, SMD, 1210, 15µH,
10% @ 2.52MHz
J.W. Miller
PM1210-150J
2
D1, D2
MBR0540T1-T
Diode-Rectifier, TH, TO220, 2PIN,
45V, 7.5A
Motorola
MBR0540T1-T
1
U1
ISL6559CR
IC-2-4 Phase Buck Controller, 32P,
MLFP, 5X5
Intersil
ISL6559CR
4
U2-U5
ISL6605CR
IC-P6 HV Synch Buck MOSFET, 8P, Intersil
QFN, 3X3
ISL6605CR
1
U8
LT1616ES6
IC-Switching Regulator, 6P, SOT23, Linear Technology
0.6A, 1.4
LT1616ES6
1
U6
MAX6509HAUK-T
IC-Temp.Switch, 5P, SOT23, 2.75.5V
MAX6509HAUK
1
U7
MC74VHC1G07DT
IC-Non-Inverting Buffer, 5P, S0T23-5 On Semiconductor
MC74VHC1G07DT
8
Q2, Q4, Q6, Q8, Q10,
Q12, Q14, Q16
IRF6607
Transis-PwrMOS, N-Channel, SMD, International Rectifier
2P, S0-8, 30V
International Rectifier
IRF6607
International Rectifier
IRF6618
10
Maxim
IRF6603
Application Note 1132
Bill of Materials
(Continued)
QTY
REFERENCE
COMPONENT
4
Q1, Q3, Q5, Q7
IRF6608
5
R16, R25, R28-R30
1
R21
3
5
1
2
R11, R12, R31
R1-R4, R9
R19
R15, R24
DESCRIPTION/COMMENT
MFG NUMBER
International Rectifier
IRF6608
H2511-00010-1/16W5-T Resistor, SMD, 0603, 1Ω, 1/16W,
5%, TF
Venkel
CR0603-16W-1R0JT
H2511-00620-1/10W5-T Resistor, SMD, 0603, 62Ω, 1/10W,
5%, TF
Panasonic
ERJ-3GEYJ620V
Venkel
CR0603-16W-620JT
H2511-00R00-1/16W-T
Transist-MOS, N-Channel, SMD,
DIRECTFET, 30V
MFG NAME
Resistor, SMD, 0603, 0Ω, 1/16W, 5%, Panasonic
TF
Venkel
H2511-01001-1/16W1-T Resistor, SMD, 0603, 1K, 1/16W,
1%, TF
ERJ-3GEY0R00V
CR0603-16W-000T
Panasonic
ERJ-3EKF1001
Samsung
RC1608F1001CS
Venkel
CR0603-16W-1001FT
Cal-chip
RM06F1002CT
Panasonic
ERJ-3EKF1002V
Venkel
CR0603-16W-1002FT
H2511-01003-1/16W1-T Resistor, SMD, 0603, 100K, 1/16W,
1%, TF
Panasonic
ERJ-3EKF1003
Venkel
CR0603-16W-1003FT
H2511-01002-1/16W1-T Resistor, SMD, 0603, 10K, 1/16W,
1%, TF
1
R13
H2511-01003-1/16W5-T Resistor, SMD, 0603, 100K, 1/16W,
5%, TF
Dale
CRCW0603-104JRT1
1
R22
H2511-01402-1/16W1-T Resistor, SMD, 0603, 14K, 1/16W,
1%, TF
NIC Comp Corp.
NRC06F1402TR
Panasonic
ERJ-3EKF1402V
H2511-01601-1/16W5-T Resistor, SMD, 0603, 1.6K, 1/16W, Panasonic
5%, TF
Venkel
ERJ-3GEYJ162V
H2511-03402-1/16W1-T Resistor, SMD, 0603, 34K, 1/16W,
1%, TF
Panasonic
ERJ-3EKF3402V
Venkel
CR0603-16W-3402FT
Yageo
9C06031A3402FKHFT
Panasonic
ERJ-3GEYJ393V
Venkel
CR0603-16W-393JT
1
1
1
1
4
2
R17
R18
R20
R23
R5-R8
R26, R27
H2511-03902-1/10W5-T Resistor, SMD, 0603, 39K, 1/10W,
5%, TF
H2511-04021-1/16W1-T Resistor, SMD, 0603, 4.02kΩ, 1/16W, Panasonic
1%,TF
Venkel
ERJ-3EKF4021V
H2511-04993-1/16W1-T Resistor, SMD, 0603, 499K, 1/16W,
1%, TF
Panasonic
ERJ-3EKF4993V
Venkel
CR0603-16W-4993FT
H2511-051R1-1/16W1-T Resistor, SMD, 0603, 51.1Ω, 1/16W, Panasonic
1%, TF
Venkel
Vishay
1
R10
H2511-07681-1/16W1-T Resistor, SMD, 0603, 7.68K, 1/16W, Panasonic
1%, TF
Venkel
Yageo
1
CR0603-16W-1601JT
Heatsink
CR0603-16W-4021FT
ERJ-3EKF51R1V
CR0603-16W-51R1FT
CRCW060351R1F100
ERJ-3EKF7681V
CR0603-16W-7681FT
9C06031A7681FKHFT
Wakefield
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 the Application Note or Technical Brief is current before proceeding.
For information regarding Intersil Corporation and its products, see www.intersil.com
11
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