ISL6260CRZ [INTERSIL]

Multiphase Core Regulator for IMVP-6 Mobile CPUs;
ISL6260CRZ
型号: ISL6260CRZ
厂家: Intersil    Intersil
描述:

Multiphase Core Regulator for IMVP-6 Mobile CPUs

开关 输出元件
文件: 总26页 (文件大小:578K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
ISL6260, ISL6260B  
®
Data Sheet  
January 3, 2006  
FN9162.1  
Multiphase Core Regulator for IMVP-6  
Mobile CPUs  
Features  
• Precision Multiphase Core Voltage Regulation  
- 0.5% System Accuracy Over Temperature  
- Enhanced Load Line Accuracy  
The ISL6260 and ISL6260B provide microprocessor core  
voltage regulation by driving up to 3 channels in parallel. The  
multiphase buck converter architecture uses interleaved  
channels to multiply the output voltage ripple frequency and  
reduce output channel currents. The reduction in ripple results  
in fewer components, lower component cost, reduced power  
dissipation, and smaller implementation area. The ISL6260,  
ISL6260B multiphase controller together with the ISL6208 gate  
drivers form the basis for a portable power supply solution to  
power Intel's next generation mobile microprocessors. The  
modulator at the heart of this power system is derived from  
• Microprocessor Voltage Identification Input  
- 7-Bit VID Input  
- 0.300V to 1.500V in 12.5mV Steps  
- Supports VID Changes On-The-Fly  
• Multiple Current Sensing Approaches Supported  
- Lossless DCR Current Sensing  
- Precision Resistive Current Sensing  
• Supports PSI# and Narrow VDC for Enhanced Battery Life  
(EBL) Initiatives  
• Superior Noise Immunity and Transient Response  
• Thermal Monitor  
3
Intersil's Robust Ripple Regulator technology, (R ) Compared  
3
with the traditional multiphase buck regulator, the R  
technology multiphase converter has faster transient response.  
This is due to the R modulator commanding variable switching  
frequency during load transients.  
• Differential Remote Voltage Sensing  
3
• High Efficiency Across Entire Load Range  
• Programmable 1, 2 or 3 Power Channels  
• Balanced Channel Loading Including Transients  
• Small Footprint QFN 40 Lead 6x6 Package  
• Pb-Free Plus Anneal Available (RoHS Compliant)  
Intel Mobile Voltage Positioning is a smart voltage regulation  
technology, which effectively reduces power dissipation in Intel  
Pentium processors. The ISL6260 and ISL6260B support the  
IMVP-6 mobile processor voltage regulation specifications.  
ISL6260 and ISL6260B are pin-to-pin compatible. ISL6260B  
responds to PSI# signal by adding or dropping PWM2 and  
adjusting overcurrent protection accordingly. To improve  
audible noise, the DPRSLPVR signal can be used to reduce  
slew rates entering and exiting Deeper Sleep.  
Applications  
• Mobile laptop computers  
Pinout  
ISL6260CRZ, ISL6260BCRZ (QFN)  
TOP VIEW  
The ISL6260 and ISL6260B have several other key features.  
Current sensing can be done using either DCR sensing or  
discrete precision resistor sensing. A single NTC thermistor  
thermally compensates both the gain and time constant of  
the DCR variation. A unity gain, differential amplifier is  
provided for remote CPU die sensing. This allows the  
voltage on the CPU die to be accurately measured and  
regulated per Intel IMVP-6 specifications.  
40 39 38 37 36 35 34 33 32 31  
1
2
30  
VID2  
PSI#  
PGD_IN  
RBIAS  
VR_TT#  
NTC  
29 VID1  
28 VID0  
3
Ordering Information  
4
27  
26  
25  
24  
23  
22  
PWM1  
PWM2  
PWM3  
FCCM  
ISEN1  
ISEN2  
TEMP.  
PART NUMBER  
(Note)  
PART  
MARKING  
RANGE  
(°C)  
PACKAGE  
(Pb-FREE)  
PKG.  
DWG. #  
5
GND PAD  
(BOTTOM)  
6
SOFT  
OCSET  
VW  
ISL6260CRZ  
ISL6260CRZ -10 to 100 40 Ld 6x6 QFN L40.6x6  
7
ISL6260CRZ-T ISL6260CRZ -10 to 100 40 Ld 6x6 QFN L40.6x6  
ISL6260BCRZ ISL6260BCRZ -10 to 100 40 Ld 6x6 QFN L40.6x6  
ISL6260BCRZ-T ISL6260BCRZ -10 to 100 40 Ld 6x6 QFN L40.6x6  
8
9
COMP  
FB  
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.  
10  
21 ISEN3  
11 12 13 14 15 16 17 18 19 20  
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.  
Copyright © Intersil Americas Inc. 2005, 2006. All Rights Reserved  
1
All other trademarks mentioned are the property of their respective owners.  
ISL6260, ISL6260B  
VW  
Functional Pin Description  
A resistor from this pin to COMP programs the switching  
frequency. (7kΩ gives approximately 300kHz). VW pin  
sources current.  
40 39 38 37 36 35 34 33 32 31  
COMP  
This pin is the output of the error amplifier.  
1
2
30  
VID2  
PSI#  
PGD_IN  
RBIAS  
VR_TT#  
NTC  
FB  
29 VID1  
28 VID0  
This pin is the inverting input of error amplifier.  
3
VDIFF  
4
27  
26  
25  
24  
23  
22  
PWM1  
PWM2  
PWM3  
FCCM  
ISEN1  
ISEN2  
This pin is the output of the differential amplifier.  
5
GND PAD  
(BOTTOM)  
VSEN  
6
SOFT  
OCSET  
VW  
Remote core voltage sense input. Connect to micro-  
processor die.  
7
8
RTN  
9
Remote voltage sensing return. Connect to ground at micro-  
processor die.  
COMP  
FB  
10  
21 ISEN3  
DROOP  
11 12 13 14 15 16 17 18 19 20  
Output of droop amplifier. Output = VO + DROOP.  
DFB  
Inverting input to droop amplifier.  
PSI#  
Low load current indicator input. When asserted low,  
indicates a reduced load-current condition. For ISL6260B,  
when PSI# is asserted low, PWM2 will be disabled.  
VO  
An input to the IC that reports the local output voltage.  
VSUM  
This pin is connected to the current summation junction.  
PGD_IN  
Digital Input. When asserted high, indicates VCCP and  
VCC_MCH voltages are within regulation. PGD_IN signal  
high is needed for the CLK_EN# to be low and PGOOD to  
be high.  
VIN  
Battery supply voltage, used for feed forward.  
VSS  
Signal ground; Connect to local controller ground.  
RBIAS  
VDD  
147K Resistor to VSS sets internal current reference.  
5V bias power.  
VR_TT#  
ISEN3  
Thermal overload output indicator.  
Individual current sensing for channel 3.  
NTC  
ISEN2  
Thermistor input to VRTT# circuit.  
Individual current sensing for channel 2.  
SOFT  
ISEN1  
A capacitor from this pin to Vss sets the maximum slew rate  
of the output voltage. Soft pin is the non-inverting input of the  
error amplifier.  
Individual current sensing for channel 1.  
FCCM  
OCSET  
Forced Continuous Conduction Mode (FCCM) enable pin to  
MOSFET drivers. It will disable diode emulation.  
Overcurrent set input. A resistor from this pin to VO sets  
DROOP voltage limit for OC trip. A 10µA current source is  
connected internally to this pin.  
PWM3  
PWM output for channel 3.  
FN9162.1  
January 3, 2006  
2
ISL6260, ISL6260B  
PWM2  
VR_ON  
PWM output for channel 2. For ISL6260B, PSI# low will  
make this output tri-state.  
Voltage Regulator enable input. A high level logic signal on  
this pin enables the regulator.  
PWM1  
DPRSLPVR  
PWM output for channel 1.  
Deeper Sleep Enable signal. A high level logic signal on this  
pin indicates that the micro-processor is in Deeper Sleep  
Mode and indicates that slow entry and exit from C4 should  
occur. DPRSLPVR low indicates large charging or  
discharging soft pin current, and therefore fast output  
voltage transitions.  
VID0, VID1, VID2, VID3, VID4, VID5, VID6  
VID input with VID0 = LSB.  
CLK_EN#  
Digital output to enable System PLL Clock; Goes active  
10µs after PG_IN is active and Vcore is within 10% of Boot  
Voltage.  
DPRSTP#  
Deeper Sleep Enable signal. A low level logic signal on this  
pin indicates that the micro-processor is in Deeper Sleep  
Mode.  
PGOOD  
Power Good open-drain output. Will be pulled up externally  
by a 680Ω resistor to VCCP or 1.9kΩ to 3.3V.  
3V3  
3.3V supply voltage for CLK_EN# logic, such an  
implementation will improve power consumption from 3.3V  
compared to open drain circuit other wise.  
FN9162.1  
January 3, 2006  
3
ISL6260, ISL6260B  
Absolute Maximum Ratings  
Thermal Information  
Supply Voltage, VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 - +7V  
Battery Voltage, VIN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +25V  
Open Drain Outputs, PGOOD, VR_TT# . . . . . . . . . . . . . -0.3 - +7V  
ALL OTHER PINS . . . . . . . . . . . . . . . . . . . . . -0.3V to (VDD + 0.3V)  
Thermal Resistance  
θ
(°C/W)  
30  
θ
(°C/W)  
5.5  
JA  
JC  
QFN Package (Notes 1, 2) . . . . . . . . .  
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . 150°C  
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C  
Maximum Lead Temperature (Soldering, 10s). . . . . . . . . . . . +300°C  
Operating Conditions  
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . .-10°C to 100°C  
Supply Voltage Range (Typical). . . . . . . . . . . . . . . . . . . . . +5V ±5%  
CAUTION: Stresses 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 sections of this specification is not implied.  
NOTES:  
1. θ is measured with the component mounted on a low effective thermal conductivity test board in free air. See Tech Brief TB379 for details.  
JA  
2. For θ , the “case temp” location is the center of the exposed metal pad on the package underside.  
JC  
Electrical Specifications Operating Conditions: VDD = 5V, T = -10°C to +100°C, unless otherwise noted.  
A
PARAMETER  
INPUT POWER SUPPLY  
+5V Supply Current  
SYMBOL  
TEST CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
I
VR_ON = 3.3V  
2.9  
3.5  
1
mA  
µA  
µA  
µA  
kΩ  
V
VDD  
VR_ON = 0V  
+3.3V Supply Current  
Battery Supply Current  
VIN Input Resistance  
Power-On-Reset Threshold  
I
No load on CLK_EN#  
VR_ON = 0V  
1
3V3  
I
1
VIN  
R
VR_ON = 3.3V  
900  
4.35  
4.15  
VIN  
POR  
V
V
rising  
falling  
4.5  
r
DD  
DD  
POR  
4.00  
-0.5  
V
f
SYSTEM AND REFERENCES  
System Accuracy  
%Error  
No load; closed loop, active mode range  
VID = 0.75V - 1.50V  
+0.5  
%
(V  
)
CC_CORE  
VID = 0.5V - 0.7375V  
VID = 0.3 - 0.4875V  
-8  
+8  
mV  
mV  
V
-15  
+15  
V
1.176  
1.200  
1.500  
0.300  
0.0  
1.224  
BOOT  
Maximum Output Voltage  
Minimum Output Voltage  
VID Off State  
V
VID = [0000000]  
VID = [1100000]  
VID = [1111111]  
V
CC_CORE(max)  
V
V
CC_CORE(min)  
V
R
Voltage  
R
= 147kΩ  
BIAS  
1.45  
1.47  
1.49  
V
BIAS  
CHANNEL FREQUENCY  
Nominal Channel Frequency  
Adjustment Range  
f
Rfset = 7kΩ, 3 channel operation, Vcomp = 2V  
285  
200  
300  
315  
500  
kHz  
kHz  
SW(nom)  
See Equation 4 Rfset selection  
AMPLIFIERS  
Droop Amplifier Offset  
Error Amp DC Gain  
-0.3  
+0.3  
150  
mV  
dB  
A
90  
18  
10  
v0  
Error Amp Gain-Bandwidth Product  
FB Input Current  
GBW  
C = 20pF  
MHz  
nA  
L
I
IN(FB)  
FN9162.1  
January 3, 2006  
4
ISL6260, ISL6260B  
Electrical Specifications Operating Conditions: VDD = 5V, T = -10°C to +100°C, unless otherwise noted. (Continued)  
A
PARAMETER  
SYMBOL  
TEST CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
ISEN  
Imbalance Voltage  
Maximum of ISENs - Minimum of ISENs  
2
mV  
nA  
Input Bias Current  
20  
SOFT CURRENT  
Soft-start current  
I
-46  
±175  
-46  
-41  
±200  
-41  
-36  
±225  
-36  
μA  
μA  
μA  
μA  
μA  
SS  
SOFT Geyserville Current  
SOFT Deeper Sleep Entry Current  
SOFT Deeper Sleep Exit Current  
SOFT Deeper Sleep Exit Current  
I
|SOFT-VDAC| >100mV  
DPRSLPVR = 3.3V  
DPRSLPVR = 3.3V  
DPRSLPVR = 0V  
GV  
I
C4  
I
I
36  
41  
46  
C4EA  
C4EB  
175  
200  
225  
POWER GOOD AND PROTECTION MONITORS  
PGOOD Low Voltage  
V
I
= 4mA  
PGOOD  
0.26  
0.4  
1
V
OL  
PGOOD Leakage Current  
PGOOD Delay  
I
PGOOD = 3.3V  
-1  
5.5  
μA  
ms  
mV  
V
OH  
tpgd  
CLK_ENABLE# LOW to PGOOD HIGH  
VO rising above setpoint for >1ms  
VO rising for >2µs  
6.8  
200  
1.7  
10  
8.1  
240  
1.725  
10.2  
4
Overvoltage Threshold  
Severe Overvoltage Threshold  
OCSET Reference Current  
OC Threshold Offset  
OV  
160  
1.675  
9.8  
H
OV  
HS  
I(Rbias) = 10µA  
μA  
mV  
mV  
mV  
DROOP rising above OCSET for >150μs  
One ISEN above another ISEN for >1.2ms  
VO falling below setpoint for >1.2ms  
-2  
Current Imbalance Threshold  
9
Undervoltage Threshold  
(VDIFF/SOFT)  
UV  
-355  
-295  
-235  
1.0  
f
LOGIC THRESHOLDS  
VR_ON, DPRSLPVR and PGD_IN  
Input Low  
V
V
V
V
V
IL(3.3V)  
VR_ON, DPRSLPVR and PGD_IN  
Input High  
V
2.3  
0.7  
IH(3.3V)  
VID0-VID6, PSI#, DPRSTP# Input  
Low  
V
0.3  
IL(1.0V)  
VID0-VID6, PSI#, DPRSTP# Input  
High  
V
IH(1.0V)  
PWM  
PWM (PWM1-PWM3) Output Low  
FCCM Output Low  
V
Sinking 5mA  
Sinking 3mA  
Sourcing 5mA  
1.0  
1.0  
V
V
V
OL(5.0V)  
VOL_FCCM  
PWM (PWM1-PWM3) and FCCM  
Output High  
V
3.5  
-1  
OH(5.0V)  
PWM Tri-State Leakage  
PWM = 2.5V  
1
μA  
THERMAL MONITOR  
NTC Source Current  
NTC = 1.3V  
V (NTC) falling  
I = 20mA  
53  
60  
1.18  
6.5  
67  
1.2  
9
μA  
V
Over-Temperature Threshold  
VR_TT# Low Output Resistance  
CLK_EN# OUTPUT LEVELS  
CLK_EN# High Output Voltage  
CLK_EN# Low Output Voltage  
1.165  
R
Ω
TT  
V
3V3 = 3.3V, I = -4mA  
I = 4mA  
2.9  
3.1  
V
V
OH  
V
0.26  
0.4  
OL  
FN9162.1  
January 3, 2006  
5
ISL6260, ISL6260B  
Typical Operating Performance 3 Phase, DCR Sense, (1) 7821, (2) 7832 per phase, 300kHz, 0.5µH  
1.46  
1.44  
1.42  
1.4  
100  
Vin =8.0V  
Vin =12.6V  
Vin =19.0V  
90  
80  
1.38  
1.36  
1.34  
1.32  
70  
Vin=8.0V  
Vin=12.6V  
Vin=19.0V  
60  
50  
1
10  
100  
0
10  
20  
30  
40  
50  
I
(A)  
OUT  
I
(A)  
OUT  
FIGURE 1. ACTIVE MODE EFFICIENCY, 3 PHASE, CCM,  
PSI# = HIGH, VID = 1.4375V  
FIGURE 2. ACTIVE MODE LOAD LINE, 3 PHASE, CCM,  
PSI# = HIGH VID= 1.435V  
1.44  
100  
90  
1.43  
Vin = 8.0V  
Vin = 12.6V  
1.42  
Vin = 19.0V  
1.41  
80  
1.4  
1.39  
1.38  
1.37  
1.36  
70  
60  
50  
Vin = 8.0V  
Vin = 12.6V  
Vin = 19.0V  
0.1  
1
10  
0
10  
20  
30  
I
(A)  
Iout (A)  
)  
OUT  
FIGURE 3. DEEPER SLEEP MODE EFFICIENCY, 3 PHASE,  
DCM OPERATION, PSI# = LOW, VID = 1.4375V  
FIGURE 4. DEEPER SLEEP MODE LOAD LINE, 3 PHASE,  
CCM, PSI# = LOW VID= 1.435V  
100  
90  
0.76  
Vin = 8.0V  
0.75  
Vin = 12.6V  
0.74  
Vin = 19.0V  
0.73  
0.72  
0.71  
0.7  
80  
70  
Vin = 8.0V  
60  
Vin = 12.6V  
0.69  
0.68  
Vin = 19.0V  
50  
0.1  
1
10  
0
10  
20  
30  
Iout (A)  
Iout(A)  
FIGURE 5. DEEPER SLEEP MODE EFFICIENCY, 3 PHASE,  
DCM OPERATION, PSI# = LOW, VID = 0.75V  
FIGURE 6. DEEPER SLEEP MODE LOAD LINE, 3 PHASE,  
DCM OPERATION, PSI# = LOW, VID = 0.75V  
FN9162.1  
January 3, 2006  
6
ISL6260, ISL6260B  
Typical Operating Performance 3 Phase, DCR Sense, (1) 7821, (2) 7832 per phase, 300kHz, 0.5µH (Continued)  
100  
90  
80  
70  
60  
50  
100  
90  
80  
70  
60  
50  
Vin =8.0V  
Vin =12.6V  
Vin =19.0V  
Vin =8.0V  
Vin = 12.6V  
Vin = 19.0V  
1
10  
100  
0.1  
1
10  
Iout (A)  
Iout (A)  
FIGURE 7. ACTIVE MODE EFFICIENCY, 2 PHASE, CCM,  
PSI# = HIGH, VID = 1.4375V  
FIGURE 8. DEEPER SLEEP MODE EFFICIENCY, 2 PHASE,  
DCM OPERATION, PSI# = LOW, VID = 1.4375V  
100  
90  
1.44  
Vin = 8.0V  
1.42  
Vin = 12.6V  
Vin = 19.0V  
1.4  
80  
1.38  
1.36  
1.34  
1.32  
70  
Vin = 8.0V  
60  
50  
Vin = 12.6V  
Vin = 19.0V  
0
10  
20  
30  
40  
50  
0.1  
1
10  
Iout (A)  
Iout (A)  
FIGURE 9. DEEPER SLEEP MODE EFFICIENCY, 2 PHASE,  
DCM OPERATION, PSI# = LOW, VID = 0.75V  
FIGURE 10. ACTIVE MODE LOAD LINE, 2 PHASE, CCM,  
PSI# = HIGH, VID = 1.435V  
0.76  
1.44  
0.75  
1.43  
Vin =8.0V  
Vin = 8.0V  
Vin =12.6V  
0.74  
1.42  
Vin = 12.6V  
Vin =19.0V  
0.73  
0.72  
0.71  
0.7  
Vin = 19.0V  
1.41  
1.4  
1.39  
1.38  
1.37  
1.36  
0.69  
0.68  
0
10  
20  
30  
0
10  
20  
30  
Iout (A)  
Iout (A)  
FIGURE 11. DEEPER SLEEP MODE LOAD LINE, 2 PHASE,  
DCM OPERATION, PSI# = LOW, VID = 1.4375V  
FIGURE 12. DEEPER SLEEP MODE LOAD LINE, 2 PHASE, DCM  
OPERATION, PSI# = LOW, VID = 0.75V  
FN9162.1  
January 3, 2006  
7
ISL6260, ISL6260B  
Typical Operating Performance  
Vout@1.4375V  
Vsoft  
Vout@1.2V  
Vout  
VR_ON  
PGD_IN  
IMVP-6 Pgood  
CLK_EN#  
FIGURE 13. SOFT-START WAVEFORM SHOWING SLEW RATE  
OF 2mV/µs, 0V TO 1.2V (BOOT VOLTAGE)  
FIGURE 14. SOFT-START WAVEFORM SHOWING CLK_EN#  
AND IMVP-6 PGOOD  
Vout  
Vin  
Vout  
FIGURE 15. 12V-18V INPUT LINE TRANSIENT RESPONSE  
FIGURE 16. SOFT-START INRUSH CURRENT, V = 8V  
IN  
FIGURE 17. 3 PHASE CURRENT BALANCE, FULL LOAD = 50A  
FIGURE 18. 2 PHASE CURRENT BALANCE, FULL LOAD = 50A  
FN9162.1  
January 3, 2006  
8
ISL6260, ISL6260B  
Typical Operating Performance (Continued)  
Vout  
COMP PIN  
FIGURE 19. TRANSIENT LOAD RESPONSE, 40A LOAD STEP  
@ 200A/µs, 3 PHASE  
FIGURE 20. TRANSIENT LOAD 3 PHASE OPERATION -  
CURRENT BALANCE  
FIGURE 21. TRANSIENT LOAD 3 PHASE OPERATION, ZOOM  
OF RISING EDGE CURRENT BALANCE  
FIGURE 22. TRANSIENT LOAD 3 PHASE OPERATION, ZOOM  
OF FALLING EDGE CURRENT BALANCE  
VID MSB  
VID MSB  
Vout  
Vout  
FIGURE 23. ISL6260, VID MSB BIT CHANGE FROM 1.4375V  
TO 0.65V SHOWING 9mV/µs SLEW RATE,  
DPRSLPVR = 0, DPRSTP# = 1  
FIGURE 24. SLEW RATE ENTERING C4, VID MSB BIT  
CHANGE FROM 1.4375V TO 0.65V SHOWING  
2mV/µs SLEW RATE, DPRSLPVR = 1, DPRSTP# = 0  
FN9162.1  
January 3, 2006  
9
ISL6260, ISL6260B  
Typical Operating Performance (Continued)  
Vout  
Vout @ 1.7V  
PWM  
DPRSTP# AND PSI#  
Vout @ 0.85V  
DPRSLPVR AND MSB  
FIGURE 25. C4 ENTRY AND EXIT SLEW RATES WITH  
DPRSLPVR AND DPRSTP# (ISL6260)  
FIGURE 26. 1.7V OVP SHOWING OUTPUT PULLED LOW TO  
0.85V AND PWM TRI_STATE  
PWM  
PWM  
Vout  
Iphase  
Pgood  
Vout  
Pgood  
FIGURE 27. UNDERVOLTAGE RESPONSE SHOWING PWM  
TRI-STATE, VOUT < VID - 300mV  
FIGURE 28. OCP - RESPONSE  
PWM  
PSI#  
CLK_EN#  
Iphase  
Vout  
Vout  
Pgood  
Phase 2  
FIGURE 29. OCP - SHORT CIRCUIT PROTECTION  
FIGURE 30. ISL6260B, PHASE ADDING AND DROPPING IN  
ACTIVE MODE, LOAD CURRENT = 15A  
FN9162.1  
January 3, 2006  
10  
ISL6260, ISL6260B  
Typical Operating Performance (Continued)  
Phase 3 current  
PSI#  
CLK_EN#  
PHASE 1 CURRENT  
Vout  
PHASE 2  
CURRENT  
PHASE 2  
PHASE 2  
FIGURE 31. ISL6260B PHASE ADDING AND DROPPING IN  
DEEPER SLEEP MODE, LOAD CURRENT = 4.35A  
FIGURE 32. ISL6260B, INDUCTOR CURRENT WAVEFORM  
WITH PHASE ADDING AND DROPPING IN DCM  
OR DEEPER SLEEP MODE  
PHASE 3  
CURRENT  
PHASE 1 CURRENT  
PHASE 2 CURRENT  
PHASE 1 CURRENT  
PHASE 2 CURRENT  
Pgood  
PHASE 2  
FIGURE 33. ISL6260B, INDUCTOR CURRENT WAVEFORM  
WITH PHASE ADDING AND DROPPING IN CCM  
OR ACTIVE MODE  
FIGURE 34. ISL6260B, OVERCURRENT DUE TO PHASE  
DROPPING  
FN9162.1  
January 3, 2006  
11  
ISL6260, ISL6260B  
Simplified Application Circuit for DCR Current Sensing  
Figure 35 shows a simplified application circuit for the  
ISL6260 or ISL6260B converter. Both the MOSFET driver IC  
and main control IC are shown. The driver has a force-  
continuous-conduction-mode (FCCM) input, that when  
disabled, allows the regulator to operate in Diode Emulation  
for improved light load efficiency.  
V+5  
VIN V+3.3  
VIN  
VDD  
RBIAS  
VIN  
3V3  
V+5  
VCC  
BOOT  
NTC  
PWM1  
PWM  
UGATE  
LO  
ISEN1  
VR_TT#  
VR_TT#  
ISL6208  
SOFT  
VIDs  
PHASE  
7
CL  
RL  
FCCM  
LGATE  
GND  
VID<0:6>  
DPRSTP#  
ISEN1  
DPRSTP#  
VO'  
VSUM  
ISL6260  
DPRSLPVR  
DPRSLPVR  
VIN  
VO  
PSI#  
PSI#  
V+5  
PGD_IN  
MCHOK  
VCC  
BOOT  
CO  
PWM2  
ISEN2  
PWM  
CLK_EN#  
VR_ON  
CLK_ENABLE#  
UGATE  
LO  
VR_ON  
ISL6208  
PHASE  
IMVP6_PWRGD  
PGOOD  
VSEN  
CL  
RL  
FCCM  
LGATE  
GND  
Remote  
Sense  
at CPU  
CORE  
ISEN2  
RTN  
VSUM  
VO'  
FCCM  
Ri  
VIN  
VDIFF  
R3  
R1  
C3  
V+5  
VCC  
FB  
BOOT  
PWM3  
ISEN3  
PWM  
C1  
C2  
UGATE  
LO  
COMP  
ISL6208  
RFSET  
VSUM  
PHASE  
VSUM  
VW  
FCCM  
GND  
CL  
RL  
LGATE  
OCSET  
GND  
DFB DROOP VO  
ISEN3  
VSUM  
VO'  
CC  
RN  
S
VO'  
FIGURE 35. TYPICAL APPLICATION CIRCUIT FOR DCR SENSING  
FN9162.1  
January 3, 2006  
12  
ISL6260, ISL6260B  
Simplified Application Circuit for Resistive Current Sensing  
Figure 36 shows a simplified application circuit for the  
ISL6260 or ISL6260B converter. Both the MOSFET drivers  
and main control IC are shown. The driver has a force  
continuous-conduction-mode (FCCM) input, that when  
disabled, allows the regulator to operate in Diode Emulation  
for improved light load efficiency.  
V
+5 V+3.3 VIN  
VIN  
VDD  
RBIAS  
3V3  
VIN  
V+5  
VCC  
BOOT  
NTC  
PWM1  
ISEN1  
PWM  
UGATE  
LO  
RSEN  
VR_TT#  
VR_TT#  
ISL6208  
SOFT  
VIDs  
PHASE  
VSUM  
7
RL  
FCCM  
LGATE  
GND  
VID<0:6>  
DPRSTP#  
DPRSLPVR  
PSI#  
ISEN1  
CL  
DPRSTP#  
VO'  
ISL6260  
DPRSLPVR  
VIN  
VO  
PSI#  
V+5  
PGD_IN  
MCHOK  
VCC  
BOOT  
CO  
PWM2  
ISEN2  
PWM  
CLK_EN#  
VR_ON  
CLK_ENABLE#  
UGATE  
LO  
RSEN  
VR_ON  
ISL6208  
PHASE  
VSUM  
IMVP6_PWRGD  
PGOOD  
VSEN  
RL  
FCCM  
LGATE  
GND  
Remote  
Sense at  
CPU  
ISEN2  
CL  
RTN  
VO'  
FCCM  
Ri  
CORE  
VIN  
VDIFF  
R3  
C3  
V+5  
VCC  
FB  
BOOT  
R1  
PWM3  
ISEN3  
PWM  
C1  
C2  
UGATE  
LO  
RSEN  
COMP  
ISL6208  
RFSET  
PHASE  
VSUM  
ISEN3  
RL  
CL  
VW  
VSUM  
VSUM  
FCCM  
LGATE  
GND  
OCSET  
GND  
DFB DROOP VO  
VO'  
VO'  
FIGURE 36. TYPICAL APPLICATION CIRCUIT FOR DISCRETE RESISTOR CURRENT SENSING  
FN9162.1  
January 3, 2006  
13  
Functional Block Diagram  
VDD  
RBIAS  
PGD_IN  
PGOOD  
3V3 CLK_EN# VIN  
ISEN1 ISEN2 ISEN3  
VIN  
VO  
VID0  
VID1  
54µA 6µA  
POWER  
IBAL  
CURRENT  
BALANCE  
CLK_EN#  
LOGIC  
PROTECTION  
GOOD  
VID2  
MONITOR  
VID3  
DAC  
DACOUT  
NTC  
VID4  
VID5  
IBAL VDIFF  
OC  
FLT  
VR_TT#  
FAST_OC OR  
WAY-OC  
1.18V  
1.2V  
-
VID6  
-
+
+
OC  
VIN  
VO  
MODE  
CONTROL  
FCCM  
2X  
VO  
VR_ON  
PSI#  
FLT  
MODULATOR  
MODE  
PWM1  
PWM2  
PWM3  
SOFT  
CONTROL  
DPRSLPVR  
DPRSTP#  
OC  
VIN  
VO  
NUMBER OF  
PHASES  
10µA  
GAIN SELECT  
(ISL6260B ONLY)  
(1, 2/3, or 1/2)  
FLT  
MODULATOR  
OCSET  
-
OC  
+
OC  
VIN  
VO  
+
VSUM  
DFB  
DROOP  
-
FLT  
MODULATOR  
+
DROOP  
+
-
1
E/A  
+
-
VO  
NUMBER OF  
PHASES  
CHANNEL  
SELECT  
+
+
CLOCK  
1
MODE  
CONTROL  
-
VIN VO  
V O VSEN  
RTN  
VDIFF  
SOFT FB  
COMP  
VW  
GND  
FIGURE 37. SIMPLIFIED BLOCK DIAGRAM  
ISL6260, ISL6260B  
Theory of Operation  
V
DD  
Operational Description  
The ISL6260 and ISL6260B are multiphase regulators  
implementing Intel® IMVP-6 protocol. They can be  
programmed for one-, two- or three-channel operation for  
microprocessor core applications up to 70A. With their  
mating gate driver, the ISL6208, the SL6260 and ISL6260B  
give optimum steady-state and transient performance.  
10mV/µs  
2mV/µs  
VR_ON  
100µs  
VBOOT  
VID COMMANDED  
VOLTAGE  
SOFT & VO  
20µs  
3
At the heart of the ISL6260 and ISL6260B is the patented R  
3
PGD_IN  
(Robust Ripple Regulator®) modulator. The R ® modulator  
combines the best features of fixed frequency PWM and  
hysteretic PWM while eliminating many of their  
CLK_EN#  
shortcomings. The ISL6260 and ISL6260B modulator  
internally synthesize an analog of the inductor ripple currents  
and use hysteretic comparators on those signals to  
determine PWM pulse widths. Operating on these large-  
amplitude, noise-free synthesized signals allows the  
ISL6260 and ISL6260B to achieve lower output ripple and  
lower phase jitter than conventional hysteretic and fixed  
PWM controllers. Unlike conventional hysteretic converters,  
the ISL6260 and ISL6260B have an error amplifier that  
allows the controller to maintain a 0.5% voltage tolerance.  
IMVP-6 PGOOD  
~7ms  
FIGURE 38. SOFT-START WAVEFORMS USING A 20nF SOFT  
CAPACITOR  
Start-up Timing  
With the controller's +5V VDD voltage above the POR  
threshold, the start-up sequence begins when VR_ON  
exceeds the 3.3V logic HIGH threshold. Approximately  
100µs later SOFT and VOUT start ramping up to the boot  
voltage of 1.2V. During this interval, the SOFT capacitor is  
charged with approximately 40µA. Therefore, if the SOFT  
capacitor is selected to be 20nF, the SOFT ramp will be at  
about 2mV/µs for a soft-start time of 600µs. Once VOUT is  
within 10% of the boot voltage and PGD_IN is HIGH for six  
PWM cycles (20µs for frequency = 300kHz), then CLK_EN#  
is pulled LOW and the SOFT capacitor is charged up with  
approximately 200µA. Therefore, VOUT slews at +10mV/µs  
to the voltage set by the VID pins. Approximately seven  
milliseconds later, PGOOD is asserted HIGH. A typical start-  
up timing is shown in Figure 38. Similar results occur if  
VR_ON or PGD_IN or both are tied to VDD, with the soft-  
start sequence starting 120µs after VDD crosses the POR  
threshold.  
The hysteresis window voltage rides on the error amplifier  
output such that a load current transient results in an  
3
increase in switching frequency to give the R regulator a  
faster response than conventional fixed frequency PWM  
controllers. The sharing of the hysteretic window voltage  
also inherently shares the transient load current between the  
phases. The individual average phase voltages are  
monitored and controlled to equally share the static current  
among the phases.  
ISL6260B disables PWM2 when PSI# is asserted low.  
ISL6260 does not drop phase with PSI# signal.  
PGD_IN - LATCH  
It should be noted that PGD_IN going low will cause the  
converter to latch off. This state will be cleared when VR_ON  
is toggled. This feature allows the converter to respond to  
other system voltage outages immediately. For ISL6260B  
only, PGD_IN de-assertion (0) during normal operation will  
make CLK_EN# go high.  
FN9162.1  
January 3, 2006  
15  
ISL6260, ISL6260B  
When using inductor DCR current sensing, a single NTC  
Static Operation  
element is used to compensate the positive temperature  
coefficient of the copper winding thus sustaining the load-line  
accuracy. Procedures to follow in determining component  
values are covered in the “Component Selection and  
Application” section of the datasheet.  
After the start sequence, the output voltage will be regulated  
to the value set by the VID inputs per Table 1. This Table is  
presented in its entirety in the Intel IMVP-6™ specification.  
The ISL6260, ISL6260B will control the no-load output voltage  
to an accuracy of ±0.5% over the range of 0.75V to 1.5V.  
In addition to the total current which is used for DROOP and  
OC, the individual channel average currents are also  
monitored and are used for balancing the load between the  
channels. The IBAL circuit will adjust the channel pulse-  
widths up or down relative to the other channels to cause the  
voltages presented to the ISEN pins to be equal.  
TABLE 1. TRUNCATED VID TABLE FOR INTEL IMVP-6™  
SPECIFICATION  
VID6  
0
VID5  
0
VID4  
0
VID3  
0
VID2  
0
VID1  
0
VID0 VOUT  
0
1
1
1
0
1
0
0
0
1
0
0
0
0
1
0
1.500V  
1.4875  
1.4375  
1.4125  
1.4000  
1.2875  
1.2000  
1.1500  
1.0000  
0.9625  
0.7500  
0.6500  
0.5000  
0.300  
Off  
0
0
0
0
0
0
0
0
0
0
1
0
The ISL6260 and ISL6260B controller can be configured for  
three-, two- or single-channel operation. To disable channel  
two and/or channel three, its PWM output pin should be tied  
to +5V VDD and the ISEN pins should be grounded. If the  
ISL6208 gate driver is populated in an unused channel, its  
PWM input pin should be opened in order to turn off its  
output. In three-channel operation, the three channel PWM's  
are 120 degrees apart, and in two-channel operation they  
are 180 degrees apart. The channel PWM frequency is  
determined by the value of RFSET as shown in the  
“Component Selection and Application” section of this  
document.  
0
0
0
0
1
1
0
0
0
1
0
0
0
0
1
0
0
0
0
0
1
1
0
0
0
0
1
1
1
0
0
1
0
1
0
0
0
1
0
1
0
1
0
1
1
1
1
0
1
0
0
0
1
0
If the controller is kept in continuous conduction mode  
(CCM), the switching frequency may not be constant but it  
can maintain the switching ripple within spec. However, it will  
be very close to the set value at high input voltage and  
heavy load conditions. Selected by setting DPRSLPVR high,  
DPRSTP# low, together with PSI# signal (see Table 2),  
discontinuous conduction mode (DCM) is allowed. In DCM,  
the ISL6260, ISL6260B commands the ISL6208 to turn off  
the lower FET after its channel current decays to zero. As  
load is further reduced, channel switching frequency will  
drop, providing optimized efficiency even at light loading.  
1
0
1
0
0
0
1
1
0
0
0
0
1
1
0
0
0
0
1
1
0
0
0
1
Off  
...  
1
Off  
1
1
1
1
1
1
1
1
1
1
0
1
Off  
1
Off  
A fully-differential amplifier allows CPU die voltage sensing  
for precise voltage control at the microprocessor die. The  
inputs to the amplifier are the VSEN and RTN pins.  
Dynamic Operation  
Refer to Figure 39. The ISL6260 and ISL6260B respond to  
changes in VID command voltage by slewing to new  
voltages with a dV/dt set by the SOFT capacitor and by the  
state of DPRSLPVR. With CSOFT = 20nF and DPRSLPVR  
HIGH, the output voltage will move at ±2mV/µs for large  
changes in voltage. For DPRSLPVR LOW, the large signal  
dV/dt will be ±10mV/µs. As the output approaches the VID  
command voltage, the dV/dt rate moderates to prevent  
overshoot. During Geyserville III transitions where there is  
one LSB VID step each 5µs, the controller will follow the VID  
command with its dV/dt rate of ±2.5mV/µs.  
As the load current increases from zero, the output voltage  
will droop from the VID table value by an amount  
proportional to current to achieve the IMVP-6 load line. The  
ISL6260 and ISL6260B provide for current to be measured  
using resistors in series with the channel inductors as shown  
in the application circuit of Figure 36 or using the intrinsic  
series resistance of the inductors as shown in the application  
circuit of Figure 35. In both cases, signals representing the  
inductor currents are summed at VSUM which is the non-  
inverting input to the DROOP amplifier shown in the block  
diagram of Figure 37. The voltage at the DROOP pin minus  
the output voltage, VO´ is thus a high-bandwidth analog of  
the total inductor current. This value is used as an input to  
the differential amplifier to achieve the IMVP-6 load line as  
well as the input to the overcurrent circuit.  
FN9162.1  
January 3, 2006  
16  
ISL6260, ISL6260B  
When PSI# is de-asserted low, ISEN2 pin is connected to  
Vout  
the ISEN pins of the operational phases internally to keep  
proper current balance and less current overshoot and  
undershoot when the disabled phase is enabled again.  
10mV/us  
-2mV/us  
DPRSTP#  
PSI#  
2mV/us  
TABLE 2. ISL6260 ISL6260B MODE OF OPERATIONS  
DPRS DPR  
LPVR STP# PSI#  
CPU  
MODE  
ISL6260  
ISL6260B  
IMVP-6  
Logic  
0
0
1
1
1
0
1
0
1
N phase CCM N phase CCM Active  
N phase CCM N-1 phase CCM Active  
DPRSLPVR  
MSB of VID  
N phase CCM N phase DCM Deeper  
sleep  
FIGURE 39. DEEPER SLEEP TRANSITION SHOWING  
DPRSLPVR’s EFFECT ON EXIT SLEW RATE  
1
0
0
N phase DCM N-1 phase DCM Deeper  
sleep  
Keeping DPRSLPVR HIGH during VID transitions will result  
in reduced dV/dt output voltage changes with resulting  
minimized audio noise. For fastest recovery from Deeper  
Sleep to Active mode, DPRSLPVR LOW achieves maximum  
dV/dt. Therefore, the ISL6260 and ISL6260B are IMVP-6  
compliant for DPRSTP# and DPRSLPVR logic.  
Other  
Logic  
0
0
1
1
0
0
1
1
1
0
1
0
N phase CCM N phase CCM  
N phase CCM N-1 phase CCM  
N phase CCM N phase CCM  
N phase CCM N-1phase CCM  
Protection  
3
Intersil's R intrinsically has voltage-feed-forward. High-  
The ISL6260 and ISL6260B provide overcurrent, overvoltage,  
and undervoltage protection. Overcurrent protection is tied to  
the voltage droop which is determined by the resistors  
selected as described in the “Component Selection and  
Application” section. After the load-line is set, the OCSET  
resistor can be selected to detect overcurrent at any level of  
droop voltage. For overcurrent less that twice the OCSET  
level, the overload condition must exist for 120µs in order to  
trip the OC fault latch. This is shown in Figure 28.  
speed input voltage steps result in insignificant output  
voltage perturbations. Refer to Figure 15 in the “Typical  
Operating Performance” section of this document for Input  
Transient Performance.  
In response to load current step increases, the ISL6260 and  
ISL6260B will transiently raise the switching frequency so  
that response time is decreased and current is shared by all  
the channels.  
For overload exceeding twice the set level, the PWM outputs  
will immediately shut off and PGOOD will go low to maximize  
protection due to hard shorts. This protection was referred to  
as way-overcurrent.  
Modes of Operation Programmed by Logic Signals  
The operational modes of ISL6260 and ISL6260B are  
related to the control signals of DPRSLPVR, DPRSTP#, and  
PSI#. ISL6260B responds PSI# signal by adding or dropping  
PWM2 and adjusting the overcurrent protection level  
accordingly. ISL6260 does not drop phases while in  
operation. For example, if the ISL6260B is initially used as  
three phase, the PSI# signal will add or drop PWM2 and  
leave PWM1 and PWM3 always in operation. Meanwhile,  
after PWM2 is dropped, the phase shift between the PWM1  
and PWM3 is adjusted from 120 degree to 180 degree and  
the overcurrent and the way-overcurrent protection level will  
be adjusted to 2/3 of the initial value. If the ISL6260B is  
initially used as two phase operation, it is suggested that  
PWM1 and PWM2 pair, not PWM1 and PWM3 pair, should  
be used such that PSI# signal will enable or disable PWM2  
with PWM1 in operation always. The overcurrent and way-  
overcurrent protection level in two-to-one phase mode  
operation will be adjusted as two to one as well. For  
ISL6260B, the DCM mode is independent of PSI#, it just  
responds to the DPRSLPVR and DPRSTP#. The following  
table shows the operation modes of ISL6260 and ISL6260B  
with combinations of control logic.  
In addition, excessive phase unbalance due to gate driver  
failure will be detected and will shut down the controller after  
1ms. The phase unbalance is detected by the voltage on the  
ISEN pins if the difference is greater than 9mV.  
Undervoltage protection is independent of the overcurrent  
limit. If the output voltage is less than the VID set value by  
300mV or more, a fault will latch after 1ms in that condition.  
The PWM outputs will turn off and PGOOD will go low. This  
is shown in Figure 27. Note that most practical core  
regulators will have the overcurrent set to trip before the -  
300mV undervoltage limit.  
There are two levels of overvoltage protection and response.  
For output voltage exceeding the set value by +200mV for  
1ms, a fault is declared. All of the above faults have the  
same action taken: PGOOD is latched low and the upper  
and lower power FETs are turned off so that inductor current  
will decay through the FET body diodes. This condition can  
be reset by bringing VR_ON low or by bringing VDD below  
POR threshold. When these inputs are returned to their high  
operating levels, a soft-start will occur.  
FN9162.1  
January 3, 2006  
17  
ISL6260, ISL6260B  
TABLE 3. SUMMARY OF THE FAULT PROTECTION AND RESET OPERATIONS OF ISL6260, ISL6260B  
FAULT DURATION  
PRIOR TO  
PROTECTION  
PROTECTION  
ACTIONS  
FAULT RESET  
VR_ON toggle or VDD toggle  
VR_ON toggle or VDD toggle  
VDD toggle  
Overcurrent  
120µs  
PWMs tri-state, Pgood latched low  
PWMs tri-state, Pgood latched low  
Way-Overcurrent  
Overvoltage 1.7V  
<2µs  
Immediately  
Low side MOSFET on until Vcore <0.85V, then PWM  
tri-state, Pgood latched low.  
Overvoltage +200mV  
Undervoltage -300mV  
Phase Current Unbalance  
Over Temperature  
1ms  
PWMs tri-state, Pgood latched low  
PWMs tri-state, Pgood latched low  
PWMs tri-state, Pgood latched low  
VR_TT# goes low  
VR_ON toggle or VDD toggle  
VR_ON toggle or VDD toggle  
VR_ON toggle or VDD toggle  
N/A  
1ms  
1ms  
Immediately  
Refer to Figure 26. The second level of overvoltage  
commanded system voltage. Depending on the state of the  
system, i.e. Start-Up or Active mode, and the state of the  
DPRSLPVR pin, one of the two currents shown in Figure 40  
will be used to charge or discharge this capacitor, thereby  
controlling the slew rate of the commanded voltage. These  
currents can be found under the Soft Current section of the  
Electrical Specification Table.  
protection behaves differently. If the output exceeds 1.7V, an  
OV fault is immediately declared, PGOOD is latched low and  
the low-side FETs are turned on. The low-side FETs will  
remain on until the output voltage is pulled down below  
0.85V at which time all FETs are turned off. If the output  
again rises above 1.7V, the process is repeated. This affords  
the maximum amount of protection against a shorted high-  
side FET while preventing output ringing below ground. The  
1.7V OV is not reset with VR_ON, but requires that VDD be  
lowered to reset. The 1.7V OC detector is active at all times  
that the controller is enabled including after one of the other  
faults occurs so that the processor is protected against high-  
side FET leakage while the FETs are commanded off.  
ISL6260(B)  
I
ERROR  
AMPLIFIER  
SS  
I
2
+
The ISL6260 and ISL6260B have a thermal throttling  
feature. If the voltage on the NTC pin goes below the 1.18V  
OT threshold, the VR_TT# pin is pulled low indicating the  
need for thermal throttling to the system oversight processor.  
No other action is taken within the ISL6260 and ISL6260B in  
response to NTC pin voltage.  
SOFT  
+
V
C
REF  
SOFT  
Fault protection is summarized in Table 3.  
FIGURE 40. SOFT PIN CURRENT SOURCES FOR FAST AND  
SLOW SLEW RATES  
Component Selection and Application  
The first current, labeled I , is given in the Specification  
SS  
Soft-Start and Mode Change Slew Rates  
Table as 41μA. This current is used during Soft-Start. The  
The ISL6260 and ISL6260B use 2 slew rates for various  
modes of operation. The first is a slow slew rate, used to  
reduce inrush current on start-up. It is also used to reduce  
audible noise when entering or exiting Deeper Sleep Mode.  
A faster slew rate is used to exit out of Deeper Sleep and to  
increase system performance by achieving active mode  
regulation more quickly. Note that the SOFT cap current is  
bidirectional and is flowing into the SOFT capacitor when the  
output voltage is commanded to rise, and out of the SOFT  
capacitor when the output voltage is commanded to fall.  
second current, I sums with I to get the larger of the two  
2
SS  
currents, labeled I  
in the Electrical Specification Table.  
GV  
This total current is typically 200μA with a minimum of  
175μA.  
The IMVP-6™ specification reveals the critical timing  
associated with regulating the output voltage. The symbol,  
Slewrate, as given in the IMVP-6™ specification, will  
determine the choice of the SOFT capacitor, C  
following equation:  
, by the  
SOFT  
I
The two slew rates are determined by commanding 1 of 2  
currents onto the SOFT pin. As can be seen in Figure 40, the  
SOFT pin has a capacitance to ground. Also, the SOFT pin  
is the input to the error amplifier and is, therefore, the  
GV  
-----------------------------------  
C
=
SOFT  
SLEWRATE  
FN9162.1  
January 3, 2006  
18  
ISL6260, ISL6260B  
Using a SLEWRATE of 10mV/μs, and the typical I  
GV  
given in the Electrical Specification Table of 200μA, C  
value,  
is  
regulation, as indicated by PGD_IN going high, CLK_EN#  
goes low, triggering an internal timer for the IMVP6_PWRGD  
signal. This timer allows IMVP6_PWRGD to go high  
approximately 7ms after CLK_EN# goes low.  
SOFT  
200μA  
-----------------  
= 0.020μF  
C
=
(EQ. 2)  
SOFT  
10mV  
----------------  
1μs  
Static Mode of Operation - Processor Die Sensing  
A choice of 0.015μF would guarantee a SLEWRATE of  
Die sensing is the ability of the controller to regulate the  
Core output voltage at a remotely sensed point. This allows  
the Voltage Regulator to compensate for various resistive  
drops in the power path and insure that the voltage seen at  
the CPU die is the correct level independent of load current.  
10mV/μs is met for minimum I  
value, given in the  
GV  
Electrical Specification Table.  
Now this choice of C  
SOFT  
will then control the start-up  
slewrate as well. One should expect the output voltage to  
slew to the Boot value of 1.2V at a rate given by the following  
The VSEN and RTN pins of the ISL6260 and ISL6260B are  
connected to Kelvin sense leads at the die of the processor  
through the processor socket. These signal names are  
Vcc_sense and Vss_sense respectively. This allows the  
Voltage Regulator to tightly control the processor voltage at  
the die, independent of layout inconsistencies and drops.  
This Kelvin sense technique provides for extremely tight load  
line regulation.  
equation:  
I
dV  
41μA  
0.015μF  
mV  
μs  
SS  
(EQ. 3)  
-------  
-------------------  
----------------------  
--------  
=
=
= 2.73  
dt  
C
SOFT  
Generally, when output voltage is approaching its steady  
state, its dv/dt will slow down to prevent overshoot. In order  
to compensate the slow-down effect, faster initial dv/dt slew  
rates can be used with small soft capacitors such as 10nF to  
achieve the desired overall dv/dt in the allocated time  
interval.  
These traces should be laid out as noise sensitive traces.  
For optimum load line regulation performance, the traces  
connecting these two pins to the Kelvin sense leads of the  
processor must be laid out away from rapidly rising voltage  
nodes (switching nodes) and other noisy traces. To achieve  
optimum performance, place common mode and differential  
mode RC filters to analog ground on VSEN and RTN as  
shown in Figure 42. The filter resistors should be in order of  
10Ω so that they do not interact with the 50kΩ input  
resistance of the differential amplifier.  
Selecting R  
BIAS  
To properly bias the ISL6260 and ISL6260B, a reference  
current is established by placing a 147kΩ, 1% tolerance  
resistor from the R  
pin to ground. This will provide a  
BIAS  
highly accurate, 10μA current source from which OCSET  
reference current can be derived.  
Care should be taken in layout that the resistor is placed  
very close to the R  
pin and that a good quality signal  
BIAS  
ground is connected to the opposite side of the R  
Due to the fact that the voltage feedback to the switching  
regulator is sensed at the processor die, there exists the  
potential of an overvoltage due to an open circuited  
feedback signal, should the regulator be operated without  
the processor installed. Due to this fact, we recommend the  
use of the Ropn1 and Ropn2 connected to Vout and ground  
as shown in Figure 42. These resistors will provide voltage  
feedback in the event that the system is powered up without  
a processor installed. These resistors are typically 100Ω.  
BIAS  
resistor. Do not connect any other components to this pin as  
this would negatively impact performance. Capacitance on  
this pin would create instabilities and is to be avoided.  
Start-up Operation - CLK_EN# and PGOOD  
The ISL6260 and ISL6260B provide a 3.3V logic output pin  
for CLK_EN#. The 3V3 pin allows for a system 3.3V source  
to be connected to separated circuitry inside the ISL6260  
and ISL6260B, solely devoted to the CLK_EN# function. The  
output is a 3.3V CMOS signal with 4mA of source and  
sinking capability. This implementation removes the need for  
an external pull-up resistor on this pin, and due to the normal  
level of this signal being a low, removes the leakage path  
from the 3.3V supply to ground through the pull-up resistor.  
This reduces 3.3V supply current, that would occur under  
normal operation with a pull-up resistor, and prolongs battery  
life. The 3.3V supply should be decoupled to digital ground,  
not to analog ground for noise immunity.  
Setting the Switching Frequency - FSET  
The R modulator scheme is not a fixed frequency PWM  
3
architecture. The switching frequency can increase during  
the application of a load to improve transient performance.  
However, it also varies slightly due changes in input and  
output voltage and output current, but this variation is  
normally less than 10% in continuous conduction mode.  
Refer to Figure 35. A resistor connected between the VW  
and COMP pins of the ISL6260 and ISL6260B adjusts the  
switching window, and therefore adjusts the switching  
frequency. The Rfset resistor that sets up the switching  
frequency of the converter operating in CCM can be  
As mentioned in the “Theory of Operation” section of this  
datasheet, CLK_EN# is logic level high at start-up until 20μs  
after the system Vccp and Vcc_mch supplies are within  
regulation, and the Vcc-core is in regulation at the Boot level.  
Approximately 20μs after these voltages are within  
FN9162.1  
January 3, 2006  
19  
ISL6260, ISL6260B  
determined using the following relationship, where Rfset is in  
kΩ and the switching period is in μs.  
eventually go up. If NTC voltage increases to 1.20V, the  
comparator will then be able to flip back. The external  
resistance difference in these two conditions is:  
(EQ. 4)  
Rfset(kΩ) = (Periods) 0.29) × 2.33  
1 .2 V  
1 .18 V  
= 2 .56 K  
54 μ A  
60 μ A  
In discontinuous conduction mode, (DCM), the ISL6260,  
ISL6260B runs in period stretching mode. It should be noted  
that the switching frequency in the Electric Table is tested  
with the error amplifier output or Comp pin voltage at 2V.  
When Comp pin voltage is lower, the switching frequency will  
not be at the tested value.  
Therefore, proper NTC thermistor has to be chosen such  
that 2.56K resistor change will be corresponding to required  
temperature hysteresis. Regular external resistor may need  
to be in series with NTC resistors to meet the threshold  
voltage values.  
Voltage Regulator Thermal Throttling  
The following is an example.  
®
®
lntel IMVP-6 technology supports thermal throttling of the  
processor to prevent catastrophic thermal damage to the  
voltage regulator. The ISL6260 and ISL6260B feature a  
thermal monitor which senses the voltage change across an  
externally placed negative temperature coefficient (NTC)  
thermistor, see Figure 41. Proper selection and placement of  
the NTC thermistor allows for detection of a designated  
temperature rise by the system.  
For Panasonic NTC with B = 4700, its resistance will drop to  
0.03322 of its nominal at 105°C, and drop to 0.03956 of its  
nominal at 100 C°. If the requirement for the temperature  
hysteresis is (105-100) C°, the required resistance of NTC  
will be:  
2 .56 K Ω  
= 404 K Ω  
(0 .03956 0 .03322  
)
Figure 41 shows the thermal throttling feature with  
hysteresis. At low temperature, SW1 is on and SW2  
connects to the 1.18V side. The total current going from NTC  
pin is 60µA. The voltage on NTC pin is higher than threshold  
voltage of 1.18V and the comparator output is low. VR_TT#  
is pulling up high by the external resistor.  
Therefore a larger value thermistor, such as 470 K NTC  
should be used.  
At 105°C, 470K NTC resistance becomes  
(0.03322*470K) = 15.6K. With 60µA on NTC pin, the voltage  
is only (15.6K*60µA) = 0.937V. This value is much lower  
than the threshold voltage of 1.18V. Therefore, a resistor is  
needed to be in series with the NTC. The required resistance  
can be calculated by:  
54µA  
6µA  
1 .18 V  
15 .6 K Ω = 4 .06 K Ω  
60 uA  
VR_TT#  
SW1  
NTC  
4.02K is a standard resistor value. Therefore, the NTC  
branch should have a 470K NTC and 4.02K resistor in  
series. The part number for the NTC thermistor is  
ERTJ0EV474J. It is a 0402 package. NTC thermistor will be  
placed in the hot spot of the board. A thermistor in an 0402  
package costs less than in an 0603 package.  
-
+
+
V
R
NTC  
NTC  
-
SW2  
1.20V  
R
s
1.18V  
INTERNAL TO  
ISL6260  
FIGURE 41. CIRCUITRY ASSOCIATED WITH THE THERMAL  
THROTTLING FEATURE OF THE ISL6260  
When temperature increases, the NTC resistor on NTC pin  
decreases. The voltage on NTC pin decreases to a level  
lower than 1.18V. The comparator changes polarity and  
turns SW1 off and throws SW2 to 1.20V. This pulls VR_TT#  
low and sends the signal to start thermal throttle. There is a  
6µA current reduction on NTC pin and 20mV voltage  
increase on threshold voltage of the comparator in this state.  
The VR_TT# signal will be used to change the CPU  
operation and decrease the power consumption. When the  
temperature goes down, the NTC thermistor voltage will  
FN9162.1  
January 3, 2006  
20  
ISL6260, ISL6260B  
Iphase1  
IS EN 1  
ISEN 2  
ISEN 3  
V dcr1  
D C R  
L1  
+
-
ISEN 3  
IS EN 2  
10uA  
IS EN 1  
O C  
R S 1  
R O C S ET  
C L1  
VSU M  
O C SE T  
R L1  
R O 1  
VO '  
-
+
ISEN 1  
L2  
VSU M  
D FB  
Iphase2  
VO '  
V SU M  
+
D C R  
Vdcr2 -  
D R O O P  
Internal to  
ISL6260  
-
R S 2  
+
R L2  
VSU M  
R O 2  
D R O O P  
+
1
1
-
+
ISEN 2  
C L2  
Σ
VO '  
+
+
-
Iphase3  
Vdcr3  
L3  
Vout  
+
-
VSE N  
R TN  
D C R  
VSU M  
VO '  
R L3  
ISEN 3  
R S3  
VD IFF  
V O '  
C bulk  
0.01uF  
R O 3  
C L3  
0.22uF  
10  
R opn1  
VO '  
to Vout  
ESR  
To Processor  
Socket K elvin  
C onnections  
VC C _S EN S E  
VSS _S EN S E  
R opn2  
FIGURE 42. EQUIVALENT MODEL FOR DROOP AND DIE SENSING USING DCR SENSING  
Figure 43 shows the simplified model of the droop circuitry.  
Essentially one resistor can replace the RO resistors of each  
phase and one RS resistor can replace the RS resistors of  
each phase. The total DCR drop due to load current can be  
replaced by a DC source, the value of which is given by  
Equation 5.  
Static Mode of Operation - Static Droop using DCR  
Sensing  
As previously mentioned, the ISL6260 and ISL6260B have  
an internal differential amplifier which provides for extremely  
accurate voltage regulation at the die of the processor. The  
load line regulation is also very accurate, and the process of  
selecting the components for the appropriate load line droop  
is explained here.  
Iout × DCR  
(EQ. 5)  
-------------------------------  
=
Vdcr  
EQV  
N
where N is the number of channels designed for Active  
operation. N = 3 for this example. Another simplification can  
be done by reducing the NTC network comprised of Rntc,  
Rseries and Rparallel, given in Figure 43, to a single resistor  
given as Rn.  
For DCR sensing, the process of compensation for DCR  
resistance variation to achieve the desired load line droop  
has several steps and is somewhat iterative. Refer to  
Figure 42.  
In Figure 42 we show a 3 phase solution using DCR  
sensing. There are two resistors around the inductor of each  
phase. These are labeled RS and RO. These resistors are  
used to arrive at the DC voltage drop across each inductor.  
Each inductor will have a certain level of DC current flowing  
through it, this current when multiplied by the DCR of the  
inductor creates a small DC level of voltage. When this  
voltage is summed with the other channels DC voltages, the  
total DC load current can be derived.  
The first step in droop load line compensation is to adjust  
Rn, RO  
and RS such that sufficient droop voltage  
EQV  
EQV  
exists even at light loads between the VSUM and VO’ nodes.  
We recognize that these components form a voltage divider.  
As a rule of thumb we start with the voltage drop across the  
Rn network, VN, to be 0.57 x Vdcr. This ratio provides for a  
fairly reasonable amount of light load signal from which to  
arrive at droop.  
First we calculate the equivalent NTC network resistance,  
Rn. Typical values that provide good performance are,  
Rseries = 3.57K_1%, Rpar = 4.53K_1% and Rntc = 10kΩ  
NTC, ERT-J1VR103J from Panasonic. Rn is then given by  
Equation 6.  
RO is typically 5 to 10Ω. This resistor is used to tie the  
outputs of all channels together and thus create a summed  
average of the local CORE voltage output. RS is determined  
through an understanding of both the DC and transient load  
currents. This value will be covered in the next section.  
(Rseries + Rntc) × Rpar  
Rseries + Rntc + Rpar  
(EQ. 6)  
--------------------------------------------------------------------  
Rn =  
= 3.4kΩ  
However, it is important to keep in mind that the output of  
each of these RS resistors are tied together to create the  
VSUM voltage node. With both the outputs of RO and RS  
tied together, the simplified model for the droop circuit can  
be derived. This is presented in Figure 43.  
In our second step we calculate the series resistance from  
each phase to the Vsum node, labeled RS1, RS2 and RS3  
in Figure 42.  
FN9162.1  
January 3, 2006  
21  
ISL6260, ISL6260B  
10uA  
OCSET  
-
+
RS  
N
OC  
RS  
=
EQV  
VSUM  
DFB  
VSUM  
+
DROOP  
-
Internal to  
ISL6260  
DCR  
N
Vdcr  
= Iout ×  
EQV  
DROOP  
+
+
VN  
-
1
1
-
+
Σ
(
Rntc + Rseries  
Rntc + Rseries  
)
)
× Rpar  
+ Rpar  
Rn =  
+
+
-
(
VO'  
RTN  
VSEN  
VDIFF  
VO'  
RO  
N
RO  
=
EQV  
FIGURE 43. EQUIVALENT MODEL FOR DROOP AND DIE SENSING USING DCR SENSING  
We do this using the assumption that we desire  
approximately a 0.57 gain from the DCR voltage, Vdcr, to the  
Rn network. We call this gain, G1.  
Rdrp2 is selected to be a 8.25k_1% resistor. Note, we  
choose to ignore the RO resistors because they do not add  
significant error.  
(EQ. 7)  
G1 = 0.57  
These values are extremely sensitive to layout and coupling  
factor of the NTC to the inductor. As only one NTC is  
required in this application, this NTC should be placed as  
close to the Channel 1 inductor as possible and PCB traces  
sensing the inductor voltage should be go directly to the  
inductor pads.  
After simplification, then RS  
equation:  
is given by the following  
EQV  
(EQ. 8)  
1
G1  
-------  
RS  
=
1 Rn = 2.56kΩ  
EQV  
Once the board has been laid out, some adjustments may  
be required to adjust the full load droop voltage. This is fairly  
easy and can be accomplished by allowing the system to  
achieve thermal equilibrium at full load, and then adjusting  
Rdrp2 to obtain the appropriate load line slope.  
The individual resistors from each phase to the VSUM node,  
labeled RS1, RS2 and RS3 in Figure 42, are then given by  
Equation 9, where N is 3, for the number of channels in  
active operation.  
To see whether the NTC has compensated the temperature  
change of the DCR, the user can apply full load current and  
wait for the thermal steady state and see how much the  
output voltage will deviate from the initial voltage reading. A  
good compensation can limit the drift to 2mV. If the output  
voltage is decreasing with temperature increase, that ratio  
between the NTC thermistor value and the rest of the  
resistor divider network has to be increased. The user  
should follow the component values and layout of NTC on  
evaluation board as much as possible to minimize  
engineering time.  
RS = N × RS  
= 7.69kΩ  
(EQ. 9)  
EQV  
Choosing RS = 7.68k_1% is a good choice. Once we know  
the attenuation of the RS and RN network, we can then  
determine the Droop amplifier Gain required to achieve the  
load line. Setting Rdrp1 = 1k_1%, then Rdrp2 is can be  
found using Equation 10.  
N × Rdroop  
DCR × G1  
(EQ. 10)  
--------------------------------  
Rdrp2 =  
1 × Rdrp1  
Setting N = 3 for 3 channel operation, Droop Impedance  
(Rdroop) = 0.0021 (V/A) as per the Intel IMVP-6  
specification, DCR = 0.0012Ω typical, Rdrp1 = 1kΩ and the  
attenuation gain (G1) = 0.57, Rdrp2 is then  
The 2.1mV/A load line should be adjusted by Rdrp2 based on  
maximum current steps, not based on small current steps like  
10A, as the droop gain might vary slightly between each 10A  
steps. Basically, if the max current is 40A, the required droop  
voltage is 84mV. The user should have 40A load current on  
the converter and look for 84mV droop. If the droop voltage is  
3 × 0.0021  
(EQ. 11)  
-----------------------------------  
Rdrp2 =  
1 × 1K = 8.21kΩ  
0.0012 × 0.57  
FN9162.1  
January 3, 2006  
22  
ISL6260, ISL6260B  
less than 84mV, for example, 80mV. The new value will be  
calculated by:  
small and vice versa. It is better to have the cap value a little  
bigger to cover the tolerance of the inductor to prevent the  
output voltage from going lower than the spec. This cap  
needs to be a high grade cap like X7R with low tolerance.  
There is another consideration in order to achieve better  
time constant match mentioned above. The NPO/COG  
(class-I) capacitors have only 5% tolerance and a very good  
thermal characteristics. But those caps are only available in  
small capacitance values. In order to use such capacitors,  
the resistors and thermistors surrounding the droop voltage  
sensing and droop amplifier has to be resized up to 10X to  
reduce the capacitance by 10X. But attention has to be paid  
in balancing the impedance of droop amplifier in this case.  
84 mV  
80 mV  
Rdrp 2 _ new  
=
(Rdrp 1 + Rdrp 2 ) Rdrp 1  
For the best accuracy, the effective resistance on the DFB  
and VSUM pins should be identical so that the bias current  
of the droop amplifier does not cause an offset voltage. In  
the example above, the resistance on the DFB pin is Rdrp1  
in parallel with Rdrop2, that is, 1K in parallel with 8.21K or  
890Ω. The resistance on the VSUM pin is Rn in parallel with  
RSeqv or 3.4K in parallel with 2.56K or 1460Ω. The  
mismatch in the effective resistances is 1460-890 = 570Ω.  
Do not let the mismatch get larger than 600Ω. To reduce the  
mismatch, multiply both Rdrp1 and Rdrp2 by the appropriate  
factor. The appropriate factor in the example is  
Dynamic Mode of Operation - Compensation  
Parameters  
1460/890 = 1.64.  
Considering the voltage regulator as a black box with a  
voltage source controlled by VID and a series impedance, in  
order to achieve the 2.1mV/A load line, the impedance  
needs to be 2.1mΩ. The compensation design has to ensure  
the output impedance of the converter be lower than 2.1mΩ.  
There is a mathematical calculation file available to the user.  
The power stage parameters such as L and Cs are needed  
as the input to calculate the compensation component  
values. Attention has be paid to the input resistor to the FB  
pin. Too high of a resistor will cause an error to the output  
voltage regulation because of bias current flowing in the FB  
pin. It is better to keep this resistor below 3K when using this  
file.  
Dynamic Mode of Operation - Dynamic Droop  
using DCR Sensing  
Droop is very important for load transient performance. If the  
system is not compensated correctly, the output voltage  
could sag excessively upon load application and potentially  
create a system failure. The output voltage could also take a  
long period of time to settle to its final value. This could be  
problematic if a load dump were to occur during this time.  
This situation would cause the output voltage to rise above  
the no load setpoint of the converter and could potentially  
damage the CPU.  
The L/DCR time constant of the inductor must be matched to  
the Rn*Cn time constant as shown in the following equation:  
Static Mode of Operation - Current Balance using  
DCR or Discrete Resistor Current Sensing  
Rn × RS  
L
EQV  
(EQ. 12)  
(EQ. 13)  
Current Balance is achieved in the ISL6260 and ISL6260B  
through the matching of the voltages present on the ISEN  
pins. The ISL6260 and ISL6260B adjust the duty cycles of  
each phase to maintain equal potentials on the ISEN pins.  
RL and CL around each inductor, or around each discrete  
current resistor, are used to create a rather large time  
constant such that the ISEN voltages have minimal ripple  
voltage and represent the DC current flowing through each  
channel’s inductor. For optimum performance, RL is chosen  
to be 10kΩ and CL is selected to be 0.22µF. When discrete  
resistor sensing is used, a capacitor of 10nF should be  
placed in parallel with RL to properly compensate the current  
balance circuit.  
-------------  
----------------------------------  
=
× Cn  
DCR  
Rn + RS  
EQV  
Solving for Cn we now have the following equation:  
L
-------------  
DCR  
----------------------------------------  
Cn =  
Rn × RS  
EQV  
----------------------------------  
Rn + RS  
EQV  
Note, RO was neglected. As long as the inductor time  
constant matches the Cn, Rn and Rs time constants as  
given above, the transient performance will be optimum. As  
in the Static Droop Case, this process may require a slight  
adjustment to correct for layout inconsistencies. For the  
example of L = 0.5μH, Cn is calculated below.  
ISL6260 and ISL6260B uses RC filter to sense the average  
voltage on phase node and forces the average voltage on  
the phase node to be equal for current balance. Even though  
the ISL6260, ISL6260B forces the ISEN voltages to be  
almost equal, the inductor currents will not be exactly equal.  
Take DCR current sensing as example, two errors have to  
be added to find the total current imbalance. 1) Mismatch of  
DCR: If the DCR has a 5% tolerance then the resistors could  
mismatch by 10% worst case. If each phase is carrying 20A  
then the phase currents mismatch by 20A*10% = 2A. 2)  
Mismatch of phase voltages/offset voltage of ISEN pins. The  
0.5μH  
-----------------  
0.0012  
------------------------------------------------  
(EQ. 14)  
Cn =  
= 28.5nF  
3.4kΩ × 2.56kΩ  
------------------------------------------  
3.4kΩ + 2.56kΩ  
The value of this capacitor is selected to be 27nF. As the  
inductors tend to have 20% to 30% tolerances, this cap  
generally will be tuned on the board by examining the  
transient voltage. If the output voltage transient has an initial  
dip, lower than the voltage required by the load line, and  
slowly increases back to the steady state, the cap is too  
FN9162.1  
January 3, 2006  
23  
ISL6260, ISL6260B  
phase voltages are within 2mV of each other by current  
balance circuit. The error current that results is given by  
current sensing resistors, and therefore is populated with a  
47pF capacitor.  
2mV/DCR. If DCR = 1mΩ then the error is 2A.  
The Rs values in the previous section, Rs = 7.68k_1% are  
sufficient for this approach.  
In the above example, the two errors add to 4A. For a two  
phase DC/DC, the currents would be 22A in one phase and  
18A in the other phase. In the above analysis, the current  
balance can be calculated with 2A/20A = 10%. This is the  
worst case calculation, for example, the actual tolerance of  
two 10% DCRs is 10%*sqrt(2) = 7%.  
Now, the input to the Droop amplifier is the Vrsense voltage.  
This voltage is given by the following equation:  
Rsense  
(EQ. 15)  
---------------------  
Vrsense =  
× Iout  
N
There are provisions to correct the current imbalance due to  
layout or to purposely divert current to certain phase for better  
thermal management. Customer can put a resistor in parallel  
with the current sensing capacitor on the phase of interest in  
order to purposely increase the current in that phase. But it is  
highly recommended for symmetrical layout.  
The gain of the Droop amplifier, G2, must be adjusted for the  
ratio of the Rsense to Droop impedance, Rdroop. We use  
the following equation:  
Rdroop  
----------------------  
(EQ. 16)  
G2 =  
× N  
Rsense  
Assuming N = 3, Rdroop = 0.0021(V/A) as per the Intel  
IMVP-6 specification, Rsense = 0.001Ω, we obtain G2 = 6.3.  
In the case the PC board trace resistance from the inductor  
to the microprocessor are not the same on all three phases,  
the current will not be balanced. On the phases that have too  
much trace resistance a resistor can be added in parallel  
with the ISEN capacitor that will correct for the poor layout.  
But it is highly recommended for symmetrical layout.  
The values of Rdrp1 and Rdrp2 are selected to satisfy two  
requirements. First, the ratio of Rdrp2 and Rdrp1 determine  
the gain G2 = (Rdrp2/Rdrp1)+1. Second, the parallel  
combination of Rdrp1 and Rdrp2 should equal the parallel  
combination of the Rs resistors. Combining these  
requirements gives:  
An estimate of the value of the resistor is:  
Rtweak = Risen* [2*Rdcr - (Rtrace - Rmin)]/[2(Rtrace - Rmin)]  
Rdrp1 = G2/(G2-1) * Rs/N  
Rdrp2 = (G2-1) * Rdrp1  
where Risen is the resistance from the phase node to the  
ISEN pin; usually 10kΩ. Rdcr is the DCR resistance of the  
inductor. Rtrace is the trace resistance from the inductor to  
the microprocessor on the phase that needs to be tweaked.  
It should be measured with a good microΩ meter. Rmin is  
the trace resistance from the inductor to the microproccessor  
on the phase with the least resistance.  
In the example above, Rs = 7.68K, N = 3, and G2 = 6.3 so  
Rdrp 3K and Rdrp2 is 15.8kΩ.  
These values are extremely sensitive to layout. Once the  
board has been laid out, some tweaking may be required to  
adjust the full load Droop. This is fairly easy and can be  
accomplished by allowing the system to achieve thermal  
equilibrium at full load, and then adjusting Rdrp2 to obtain  
the desired Droop value.  
For example, if the PC board trace on one phase is 0.5mΩ  
and on another trace is 0.3mΩ; and if the DCR is 1.2mΩ;  
then the tweaking resistor is Rtweak = 10kΩ * [1.2*2 -  
(0.5-0.3)]/[2*(0.5-0.3)] = 55kΩ.  
Fault Protection - Overcurrent Fault Setting  
Droop using Discrete Resistor Sensing - Static/  
Dynamic Mode of Operation  
As previously described, the overcurrent protection of the  
ISL6260, ISL6260B is related to the Droop voltage.  
Previously we have calculated that the Droop Voltage =  
ILoad * Rdroop, where Rdroop is the load line slope  
specified as 0.0021 (V/A) in the Intel IMVP-6 specification.  
Knowing this relationship, the overcurrent protection  
threshold can be set up as a voltage Droop level. Knowing  
this voltage droop level, one can program in the appropriate  
drop across the Roc resistor. This voltage drop will be  
referred to as Voc. Once the droop voltage is greater than  
Voc, the PWM drives will turn off and PGOOD will go low.  
When choosing current sense resistor, not only the tolerance  
of the resistance is important, but also the TCR. And its  
combined tolerance at a wide temperature range should be  
calculated.  
Figure 44 shows the equivalent circuit of a discrete current  
sense approach. Figure 36 shows a more detailed  
schematic of this approach. Droop is solved the same way  
as the DCR sensing approach with a few slight  
modifications.  
First, there is no NTC required for thermal compensation,  
therefore, the Rn resistor network in the previous section is  
not required. Secondly, there is no time constant matching  
required, therefore, the Cn component is not matched to the  
L/DCR time constant, but this component does indeed  
provide noise immunity, especially due to the ESL of the  
The selection of Roc is given below in Equation 17.  
Assuming we desire an overcurrent trip level, Ioc, of 55A,  
and knowing from the Intel Specification that the load line  
FN9162.1  
January 3, 2006  
24  
ISL6260, ISL6260B  
Voc  
10uA  
OCSET  
Roc  
-
+
OC  
RS  
N
RSEQV  
=
VSUM  
DFB  
VSUM  
+
DROOP  
-
Internal to  
ISL6260  
DROOP  
Rsense  
N
+
+
VN  
-
1
1
VrsenseEQV = Iout×  
-
+
Σ
+
+
-
RO  
VO'  
RTN  
VSEN  
ROEQV  
=
VDIFF  
VO'  
N
FIGURE 44. EQUIVALENT MODEL FOR DROOP AND DIE SENSING USING DISCRETE RESISTOR SENSING  
slope, Rdroop is 0.0021 (V/A), we can then calculate for Roc  
as shown in Equation 17.  
Ioc × Rdroop  
55 × 0.0021  
10x10  
------------------------------------  
------------------------------  
= 11.5KΩ  
(EQ. 17)  
Roc =  
=
6  
10μA  
Note, if the droop load line slope is not -0.0021 (V/A) in the  
application, the overcurrent setpoint will differ from  
predicted.  
A capacitor may be added in parallel with Roc to improve  
noise rejection but the Roc*capacitor time constant cannot  
exceed 20µs. Do not remove Roc if overcurrent protection is  
not desired. The maximum Roc is 30K.  
FN9162.1  
January 3, 2006  
25  
ISL6260, ISL6260B  
Quad Flat No-Lead Plastic Package (QFN)  
Micro Lead Frame Plastic Package (MLFP)  
L40.6x6  
40 LEAD QUAD FLAT NO-LEAD PLASTIC PACKAGE  
(COMPLIANT TO JEDEC MO-220VJJD-2 ISSUE C)  
2X  
0.15  
C A  
MILLIMETERS  
D
A
SYMBOL  
MIN  
NOMINAL  
MAX  
1.00  
0.05  
1.00  
NOTES  
9
D/2  
A
A1  
A2  
A3  
b
0.80  
0.90  
-
D1  
-
-
-
-
D1/2  
2X  
-
9
N
0.15 C  
B
6
0.20 REF  
9
INDEX  
AREA  
1
2
3
E1/2  
E/2  
9
0.18  
3.95  
3.95  
0.23  
0.30  
4.25  
4.25  
5, 8  
D
6.00 BSC  
-
E1  
E
B
D1  
D2  
E
5.75 BSC  
9
2X  
4.10  
7, 8  
0.15 C  
B
6.00 BSC  
-
2X  
TOP VIEW  
E1  
E2  
e
5.75 BSC  
9
0.15 C  
A
4.10  
7, 8  
0
A2  
4X  
C
A
/ /  
0.10 C  
0.08 C  
0.50 BSC  
-
k
0.25  
0.30  
-
-
0.40  
-
-
-
L
0.50  
0.15  
8
SEATING PLANE  
A3 A1  
SIDE VIEW  
9
L1  
N
10  
5
40  
10  
10  
-
2
NX b  
0.10 M C A B  
4X P  
Nd  
Ne  
P
3
D2  
D2  
8
7
3
NX k  
(DATUM B)  
-
-
0.60  
12  
9
2
N
θ
-
9
4X P  
1
Rev. 1 10/02  
(DATUM A)  
2
3
(Ne-1)Xe  
REF.  
NOTES:  
E2  
6
1. Dimensioning and tolerancing conform to ASME Y14.5-1994.  
2. N is the number of terminals.  
INDEX  
AREA  
7
8
E2/2  
NX L  
8
3. Nd and Ne refer to the number of terminals on each D and E.  
4. All dimensions are in millimeters. Angles are in degrees.  
N
e
9
(Nd-1)Xe  
REF.  
CORNER  
OPTION 4X  
5. Dimension b applies to the metallized terminal and is measured  
between 0.15mm and 0.30mm from the terminal tip.  
BOTTOM VIEW  
6. The configuration of the pin #1 identifier is optional, but must be  
located within the zone indicated. The pin #1 identifier may be  
either a mold or mark feature.  
A1  
NX b  
5
7. Dimensions D2 and E2 are for the exposed pads which provide  
improved electrical and thermal performance.  
C
L
SECTION "C-C"  
8. Nominal dimensionsare provided toassistwith PCBLandPattern  
Design efforts, see Intersil Technical Brief TB389.  
C
L
9. Features and dimensions A2, A3, D1, E1, P & θ are present when  
Anvil singulation method is used and not present for saw  
singulation.  
L
L
10  
10  
L1  
L1  
10. Depending on the method of lead termination at the edge of the  
package, a maximum 0.15mm pull back (L1) maybe present. L  
minus L1 to be equal to or greater than 0.3mm.  
e
e
C
C
TERMINAL TIP  
FOR ODD TERMINAL/SIDE  
FOR EVEN TERMINAL/SIDE  
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  
FN9162.1  
January 3, 2006  
26  

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