2/3/4 Phase Buck Controller
for VR10 and VR11 Pentium
IV Processor Applications
The NCP5388 is a two−, three−, or four−phase buck controller
which combines differential voltage and current sensing, and
adaptive voltage positioning to power Intel’s most demanding
Pentium® IV Processors and low voltage, high current power
supplies. Dual−edge pulse−width modulation (PWM) combined with
inductor current sensing reduces system cost by providing the fastest
initial response to transient loads thereby requiring less bulk and
ceramic output capacitors to satisfy transient load−line requirements.
A high performance operational error amplifier is provided, which
allows for easy compensation of the system. The proprietary method
of Dynamic Reference Injection (Patent Pending) makes the error
amplifier compensation virtually independent of the system response
to VID changes, eliminating the need for tradeoffs between load
transients and Dynamic VID performance.
Features
• Meets Intel’s VR 10.0, 10.1, 10.2, and 11.0 Specifications
• Dual−Edge PWM for Fastest Initial Response to Transient Loading
• High Performance Operational Error Amplifier
• Supports both VR11 and Legacy VR10 Soft−Start Modes
• Dynamic Reference Injection (Patent Pending)
• 8−Bit DAC per Intel’s VR11 Specifications
• DAC Range from 0.5 V to 1.6 V
• "0.75% System Voltage Accuracy
• Remote Temperature Sensing per VR11
• 2, 3, or 4−Phase Operation
• True Differential Remote Voltage Sensing Amplifier
• Phase−to−Phase Current Balancing
• “Lossless” Differential Inductor Current Sensing
• Differential Current Sense Amplifiers for each Phase
• Adaptive Voltage Positioning (AVP)
• Fixed No−Load Voltage Positioning at –19 mV
• Frequency Range: 100 kHz–1.0 MHz
• Latched Overvoltage Protection (OVP)
• Threshold Sensitive Enable Pin for VTT Sensing
• Power Good Output with Internal Delays
• Programmable Soft−Start Time
• Operates from 12 V
• This is a Pb−Free Device*
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MARKING
DIAGRAM
1
1
40
40 PIN QFN, 7x7
MN SUFFIX
CASE 488AG
NCP5388 = Specific Device Code
AA= Assembly Location
WL= Wafer Lot
YY= Year
WW= Work Week
G/G= Pb−Free Package
*Pin 41 is the thermal pad on the bottom of the device.
ORDERING INFORMATION
DevicePackageShipping
NCP5388MNR2GQFN−40
(Pb−Free)
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specification
Brochure, BRD8011/D.
1ENPull this pin high to enable controller. Pull this pin low to disable controller. Either an open−collector output
2 – 9VID0–VID7Voltage ID DAC inputs.
10VR10/VR11VR select bit. Connect this pin to VTT (1.25 V) to select the VR11 DAC table. Ground this pin to select the
11SSA capacitor from this pin to ground programs the soft−start time.
12ROSCA resistance from this pin to ground programs the oscillator frequency. Also, this pin supplies a regulated
13ILIMOver current shutdown threshold. To program the shutdown threshold, connect this pin to the R
14AGNDPower supply return for the analog circuits that control output voltage.
15VS+Non−inverting input to the internal differential remote V
16VS−Inverting input to the internal differential remote V
17DIFFOUTOutput of the differential remote sense amplifier.
18COMPOutput of the error amplifier.
19VFBError amplifier inverting input. Connect a resistor from this pin to DIFFOUT. The value of this resistor and the
20VDRPCurrent signal output for Adaptive Voltage Positioning (AVP). The voltage of this pin minus 1.3 V is
21, 23,
CSxNInverting input to current sense amplifier #x, x = 1, 2, 3, 4.
25, 27
22, 24,
CSxNon−inverting input to current sense amplifier #x, x = 1, 2, 3, 4.
26, 28
29DRVONGate Driver enable output. This pin produces a logic HIGH to enable gate drivers and a logic LOW to disable
30 – 33G1 – G4PWM control signal outputs to gate drivers.
34VREFVoltage reference pin. This pin may be used to implement remote NTC temperature sensing as shown in the
35DGNDPower supply return for the digital circuits. Connect to AGND.
36VCCPower for the internal control circuits.
37VR_RDYVoltage Regulator Ready (PowerGood) output. Open drain type output with internal delays that will transition
38NTCRemote temperature sense connection. Connect an NTC thermistor from this pin to GND and a resistor from
39VR_FANOpen drain type of output that will be low impedance when the voltage at the NTC pin is above 1.416 V.
40VR_HOTOpen drain type of output that will be low impedance when the voltage at the NTC pin is above 1.086 V.
41THPADCopper pad on the bottom of the IC for heatsinking. This pin should be connected to the ground plane under
(with a pull−up resistor) or a logic gate (CMOS or totem−pole output) may be used to drive this pin. A Low to
High transition on this pin will initiate a soft start. If the Enable function is not required, this pin should be tied
directly to VREF.
VR10 DAC table with VR11 type startup. Connect this pin to V
legacy VR10 type startup.
(4 V) to select VR10 DAC table with
REF
2.0 V which may be used with a voltage divider to the ILIM pin to set the over current shutdown threshold as
shown in the Applications Schematics.
pin via a
resistor divider as shown in the Applications Schematics. To disable the over current feature connect this pin
directly to the R
generated by the R
amount of current from the droop resistor (R
load.
pin. To guarantee correct operation, this pin should only be connected to the voltage
OSC
pin – do not connect this pin to any externally generated voltages.
OSC
sense amplifier.
CORE
sense amplifier.
CORE
) will set the amount of output voltage droop (AVP) during
DRP
OSC
proportional to the output current. Connect a resistor from this pin to VFB to set the amount of AVP current
into the feedback resistor (RFB) to produce an output voltage droop. Leave this pin open for no AVP.
gate drivers and has an internal 70 k to ground.
Applications Schematic.
High when V
and Low when V
mV until VCC is removed.
this pin to V
is higher than 300 mV below DAC, Low when V
CORE
REF
is higher than DAC+185 mV. This output is latched Low if V
CORE
. As the NTC’s temperature increases the voltage on this pin will decrease.
is lower than 380 mV below DAC,
CORE
exceeds DAC+185
CORE
This pin will transition to a high impedance state when the voltage at the NTC pin decreases below 1.176 V.
This pin will transition to a high impedance state when the voltage at the NTC pin decreases below 0.846 V.
the IC.
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NCP5388
MAXIMUM RATINGS
RatingValueUnit
Operating Ambient Temperature Range0 to 70°C
Operating Junction Temperature Range0 to 85°C
Storage Temperature Range−55 to 150°C
Lead Temperature Soldering, Reflow (60 to 120 seconds minimum above 237°C):260°C
Thermal Resistance, Junction−to−Ambient (R
JEDEC Moisture Sensitivity Level≤ 3MSL
Maximum Voltage – VCC pin with respect to AGND15V
Maximum Voltage – all other pins with respect to AGND5.5V
Minimum Voltage – all pins with respect to AGND−0.3V
Maximum Current into pins: COMP, VDRP, DIFFOUT, VREF3.0mA
Maximum Current into pins: VR_RDY, G1, G2, G3, G4, SS, VR_FAN, VR_HOT, DRVON20mA
Maximum Current out of pins: COMP, VDRP, DIFFOUT, ROSC, VREF3.0mA
Maximum Current out of pins: G1, G2, G3, G420mA
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
NOTE: ESD Senstive Device.
) on a thermally conductive PCB in free air83°C/W
θ
JA
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Page 9
NCP5388
ELECTRICAL CHARACTERISTICS
(0°C < T
< 70°C; 0°C < T
A
ParameterTest ConditionsMinTy pMaxUnits
Error Amplifier
Input Bias Current−200−50−10nA
Inverting Input Voltage1.0 k between VFB and COMP Pins−1.3−V
Input Offset Voltage (Note 1)−1.0−1.0mV
Open Loop DC Gain (Note 1)CL = 60 pF to GND,
Open Loop Unity Gain Bandwidth
(Note 1)
Open Loop Phase Margin (Note 1)CL = 60 pF to GND,
Slew Rate (Note 1)Vin = 100 mV, G = −1.0 V/V,
Maximum Output VoltageI
Minimum Output VoltageI
Output Source Current (Note 1)V
Output Sink Current (Note 1)V
Remote Sense Differential Amplifier
VS+ Input Resistance (Note 1)DRVON = High
VS+ Input Open Circuit Voltage
(Note 1)
VS− Input Resistance (Note 1)VS+ = DAC Voltage
VS− Input Open Circuit Voltage
(Note 1)
Input Voltage Range−0.3−3.0V
Input Offset Voltage (Note 1)−1.0−1.0mV
−3dB Bandwidth (Note 1)CL = 80 pF to GND,
DC GainI
Slew Rate (Note 1)Vin = 1.0 V,
Maximum Output VoltageI
Minimum Output VoltageI
Output Source Current (Note 1)V
Output Sink Current (Note 1)V
1. Guaranteed by design. Not tested in production.
< 85°C; 10.8 V < VCC < 13.2 V; All DAC Codes; C
J
RL = 10 k to GND
CL = 60 pF to GND,
RL = 10 k to GND
RL = 10 k to GND
1.2 V < V
< 2.2 V,
out
CL = 60 pF,
DC Load = ±125 A
= 1.0 mA3.03.3−V
SOURCE
= 1.0 mA−0.91.0V
SINK
= 3.0 V−2.0−mA
out
= 1.0 V−2.0−mA
out
DRVON = Low
DRVON = High
DRVON = Low
DRVON = High
DRVON = High
VS+ = DAC Voltage
RL = 10 k to GND
= 100 A0.9821.0001.018V/V
DIFFOUT
V
= 1.0 V to 2.0 V,
out
CL = 80 pF to GND,
Load = ±125 A
= 1.0 mA3.0−−V
SOURCE
= 1.0 mA−−0.5V
SINK
= 2.1 V−25−mA
out
= 1.0 V−1.4−mA
out
= 0.1 F, FSW = 400 kHz, unless otherwise stated)
VCC
−78−dB
−15−MHz
−65−deg
−5.0−V/s
−
−
−
−
17
0.5
0.67
0.05
−
−
−
−
−10−k
=
0.333*DA
C
+ 0.433
−12−MHz
−10−V/s
k
V
V
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NCP5388
ELECTRICAL CHARACTERISTICS
(0°C < T
< 70°C; 0°C < T
A
ParameterUnitsMaxTypMinTest Conditions
V
Adaptive Voltage Positioning Amplifier
DRP
Current Sense Input to V
Current Sense Input to V
−3dB Bandwidth (Note 1)
Current Sense Input to V
Slew Rate (Note 1)
Current Summing Amp Output Offset
Voltage
Maximum V
Minimum V
Output VoltageCSx − CSxN = 0.12 V
DRP
Output VoltageCSx − CSxN = −0.12 V
DRP
Output Source Current (Note 1)VDRP = 2.9 V−9.0−mA
Output Sink Current (Note 1)VDRP = 1.0 V−2.0−mA
Current Sense Amplifiers
Input Bias CurrentCSx = CSxN = 1.4 V−200−100−nA
Common Mode Input Voltage Range
(Note 1)
Differential Mode Input Voltage Range−120−120mV
Input Offset Voltage (Note 1)CSx = CSxN = 1.0 V−3.0−3.0mV
Current Sense Input to
PWM Comparator Input Gain
Oscillator
Switching Frequency Range (Note 1)100−1000kHz
Switching Frequency Accuracy
(Note 1)
Switching Frequency AccuracyR
Switching Frequency AccuracyR
Switching Frequency AccuracyR
Switching Frequency Accuracy
(Note 1)
Switching Frequency AccuracyR
Switching Frequency AccuracyR
Switching Frequency AccuracyR
R
Output Voltage10 k < R
OSC
R
Output Voltage (Note 1)49.9 k < R
OSC
1. Guaranteed by design. Not tested in production.
< 85°C; 10.8 V < VCC < 13.2 V; All DAC Codes; C
J
Gain−60 mV < (CSx−CSxN)
DRP
DRP
Output
< +60 mV, T
CL = 330 pF to GND,
= 25°C
A
RL = 10 k to GND
DRP
Output
V(CSx−CSxN) = 25 mV (all phases),
1.3 V < V
< 1.9 V,
out
CL = 330 pF to GND,
Load = ±400 A
CSx – CSxN = 0, CSx =1.0 V−40−+40mV
(all phases),
I
SOURCE
= 1.0 mA
(all phases),
I
= 1.0 mA
SINK
0 mV < (CSx−CSxN) < 25 mV
T
= 25°C
A
R
= 100 k, 2 or 4−phase93.6104114.4kHz
OSC
= 49.9 k, 2 or 4−phase184.5205225.5kHz
OSC
= 24.9 k, 2 or 4−phase360400440kHz
OSC
= 10 k, 2 or 4−phase8299211013kHz
OSC
R
= 100 k, 3−phase9010011 0kHz
OSC
= 49.9 k, 3−phase178.2198217.8kHz
OSC
= 24.9 k, 3−phase351390429kHz
OSC
= 10 k, 3−phase8189091000kHz
OSC
< 49.9 k1.922.002.08V
OSC
< 100 k−2.00−V
OSC
= 0.1 F, FSW = 400 kHz, unless otherwise stated)
VCC
5.76.06.3V/V
−7.2−MHz
−3.7−V/s
3.02−−V
−−0.5V
−0.3−2.0V
5.76.06.3V/V
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NCP5388
ELECTRICAL CHARACTERISTICS
(0°C < T
< 70°C; 0°C < T
A
ParameterUnitsMaxTypMinTest Conditions
Modulators (PWM Comparators)
Minimum Pulse WidthFs = 400 kHz−3040ns
Magnitude of the PWM Ramp−1.0−V
0% Duty CycleCOMP voltage when the PWM
100% Duty CycleCOMP voltage when the PWM
Minimum PWM Linear Duty Cycle
(Note 1)
PWM Comparator Offset Mismatch
(Note 1)
Phase Angle ErrorBetween adjacent phases,
Propagation Delay (Note 1)Ramp/Comp crossing to Gx high−20−ns
Propagation Delay (Note 1)Ramp/Comp crossing to Gx low−20−ns
PWM Outputs
Output High VoltageSourcing 500 A3.34.04.7V
Output Low VoltageSinking 500 A−25100mV
Rise TimeCL = 20 pF, Vo = 0.3 to 2.0 V−10−ns
Fall TimeCL = 20 pF, Vo = Vmax to 0.7 V−10−ns
Output Impedance – LO StateResistance to GND (Gx = LO)−50−
1. Guaranteed by design. Not tested in production.
< 85°C; 10.8 V < VCC < 13.2 V; All DAC Codes; C
J
= 10 mA−−0.4V
SINK
C
= 20 pF,
LOAD
Vo = 10% to 90%
k to 5.0 V,
t
≤ 3 x t
R_VCC
100 s ≤ t
R_5V
R_VCC
,
≤ 20 ms
DAC = 1.3 V
VR_FAN output pulls low
VR_FAN output is open
External Pullup resistor of 2.0 k to 5.0
V,
t
≤ 3 x t
R_VCC
100 s ≤ t
= 4.0 mA−−0.3V
SINK
R_5V
R_VCC
,
≤ 20 ms
VR_FAN = 5.0 V
VR_HOT output pulls low
VR_HOT output is open
External Pullup resistor of 2.0 k to 5.0
V,
t
≤ 3 x t
R_VCC
100 s ≤ t
= 4.0 mA−−0.3V
SINK
R_5V
R_VCC
,
≤ 20 ms
VR_HOT = 5.0 V
= 0.1 F, FSW = 400 kHz, unless otherwise stated)
VCC
−−150ns
−−1.0V
−300−mV below
0.35180.36250.3737
0.28920.30250.3112
−−1.0V
−−1.0A
0.27320.28150.2897
0.21070.21900.2272
−−1.0V
−−1.0A
DAC
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NCP5388
ELECTRICAL CHARACTERISTICS
(0°C < T
< 70°C; 0°C < T
A
ParameterUnitsMaxTypMinTest Conditions
Soft−Start
SS Pin Source CurrentENABLE = HI, V
SS Pin Source CurrentENABLE = HI, V
Soft−Start Ramp TimeCSS = 0.01 F, DRVON = HI to V
SS Pin Discharge VoltageENABLE = LO−−50mV
Soft−Start Discharge TimeFrom ENABLE = LO to V
VR11 V
Threshold Voltage−1.081−V
BOOT
VR11 Dwell Time at V
Enable Input
Enable High Input Leakage CurrentEN = 3.0 V−−10A
Upper ThresholdV
Lower ThresholdV
Total HysteresisV
Enable Delay TimeEnable transitioning HI to start of SS
Disable Delay TimeEnable transitioning Low to
Current Limit
Current Sense Inputs to I
ILIM Pin Input Bias CurrentV
ILIM Pin Working Voltage Range0.3−2.0V
ILIM Input Offset Voltage−50−50mV
Overvoltage Protection
Overvoltage ThresholdDAC+160DAC+180DAC+200mV
Undervoltage Protection
UVLO Start Threshold8.29.09.5V
UVLO Stop Threshold7.28.08.5V
UVLO Hysteresis−1.0−V
VID Inputs
Upper ThresholdV
Lower ThresholdV
Input Bias CurrentV
Delay before Latching VID Change
(VID De−Skewing)
< 85°C; 10.8 V < VCC < 13.2 V; All DAC Codes; C
J
< 1.1 V−5.0−A
SS PIN
> 1.15 V, VR11
SS mode only
SS PIN
= 1.1 V
Discharge Voltage,
SS PIN
SS PIN
< max
= 0.1 F, FSW = 400 kHz, unless otherwise stated)
VCC
125−−A
1.52.23.0ms
−5.0−s
CSS = 0.01 F
(Note 1)50225900s
BOOT
UPPER
LOWER
UPPER
– V
LOWER
0.800.850.90V
0.670.750.83V
70100130mV
0.51.53.0ms
voltage rise
−−200ns
DRVON = Low
Gain20 mV < (CSx−CSxN) < 60 mV
LIM
T
= 25°C
A
(all CS channels together)
= 2.0 V−0.11.0A
ILIM
UPPER
LOWER
= 1.25 V−100500nA
VIDX
Measured from the 1st edge of a VID
5.76.06.3V/V
−−800mV
400−−mV
500−1000ns
change
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NCP5388
ELECTRICAL CHARACTERISTICS
(0°C < T
< 70°C; 0°C < T
A
ParameterUnitsMaxTypMinTest Conditions
VR10/VR11 Select
VR10/VR11 DAC Table Threshold0.4−0.775V
VR10 w/ Legacy SS/VR11 Threshold2.7−3.1V
Internal DAC Slew Rate Limiter
Positive Slew Rate LimitVID step range of +10mV to +500mV−7.3−mV/s
Negative Slew Rate LimitVID step range of −10mV to −500mV−7.3−mV/s
Voltage Reference (V
V
Output Voltage0 < I
REF
Input Supply Current
VCC Operating CurrentFSW = 400 kHz−20−mA
< 85°C; 10.8 V < VCC < 13.2 V; All DAC Codes; C
J
)
REF
< 250 A3.924.004.08V
VREF
= 0.1 F, FSW = 400 kHz, unless otherwise stated)
VCC
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NCP5388
ELECTRICAL CHARACTERISTICS
(0°C < T
< 70°C; 0°C < T
A
ParameterUnitsMaxTypMinTest Conditions
VR10 DAC
System Voltage Accuracy1.0 V < DAC < 1.6 V
No−Load Offset Voltage from
Nominal DAC Specification
VR10 VID Codes
VID4
400 mV
01010111.60000
01010101.59375
01011011.58750
01011001.58125
01011111.57500
01011101.56875
01100011.56250
01100001.55625
01100111.55000
01100101.54375
01101011.53750
01101001.53125
01101111.52500
01101101.51875
01110011.51250
01110001.50625
01110111.50000
01110101.49375
01111011.48750
01111001.48125
01111111.47500
01111101.46875
10000011.46250
10000001.45625
10000111.45000
10000101.44375
10001011.43750
10001001.43125
10001111.42500
10001101.41875
10010011.41250
10010001.40625
10010111.40000
10010101.39375
10011011.38750
10011001.38125
10011111.37500
< 85°C; 10.8 V < VCC < 13.2 V; All DAC Codes; C
J
0.8 V < DAC < 1.0 V
0.5 V < DAC < 0.8 V
With CS Input Vin = 0 V−19mV
VID3
200 mV
VID2
100 mV
VID1
50 mV
VID0
25 mV
= 0.1 F, FSW = 400 kHz, unless otherwise stated)
VCC
−−±0.75
±7.0
±8.0
VID5
12.5 mV
VID6
6.25 mV
%
mV
mV
Nominal DAC
Voltage (V)
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NCP5388
VR10 VID Codes
VID4
400 mV
10011101.36875
10100011.36250
10100001.35625
10100111.35000
10100101.34375
10101011.33750
10101001.33125
10101111.32500
10101101.31875
10110011.31250
10110001.30625
10110111.30000
10110101.29375
10111011.28750
10111001.28125
10111111.27500
10111101.26875
11000011.26250
11000001.25625
11000111.25000
11000101.24375
11001011.23750
11001001.23125
11001111.22500
11001101.21875
11010011.21250
11010001.20625
11010111.20000
11010101.19375
11011011.18750
11011001.18125
11011111.17500
11011101.16875
11100011.16250
11100001.15625
11100111.15000
11100101.14375
11101011.13750
11101001.13125
11101111.12500
11101101.11875
11110011.11250
11110001.10625
11110111.10000
11110101.09375
1111101OFF
1111100OFF
VID3
200 mV
VID2
100 mV
VID1
50 mV
VID0
25 mV
VID5
12.5 mV
VID6
6.25 mV
Nominal DAC
Voltage (V)
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NCP5388
VR10 VID Codes
VID4
400 mV
1111111OFF
1111110OFF
00000011.08750
00000001.08125
00000111.07500
00000101.06875
00001011.06250
00001001.05625
00001111.05000
00001101.04375
00010011.03750
00010001.03125
00010111.02500
00010101.01875
00011011.01250
00011001.00625
00011111.00000
00011100.99375
00100010.98750
00100000.98125
00100110.97500
00100100.96875
00101010.96250
00101000.95625
00101110.95000
00101100.94375
00110010.93750
00110000.93125
00110110.92500
00110100.91875
00111010.91250
00111000.90625
00111110.90000
00111100.89375
01000010.88750
01000000.88125
01000110.87500
01000100.86875
01001010.86250
01001000.85625
01001110.85000
01001100.84375
01010010.83750
01010000.83125
VID3
200 mV
VID2
100 mV
VID1
50 mV
VID0
25 mV
VID5
12.5 mV
VID6
6.25 mV
Nominal DAC
Voltage (V)
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NCP5388
ELECTRICAL CHARACTERISTICS
(0°C < T
< 70°C; 0°C < T
A
ParameterTest ConditionsMinTy pMaxUnits
VR 11 DAC
System Voltage Accuracy1.0 V < DAC < 1.6 V
No−Load Offset Voltage from
Nominal DAC Specification
Table 2: VR11 VID Codes
VID7
800 mV
00000000OFF00
00000001OFF01
000000101.6000002
000000111.5937503
000001001.5875004
000001011.5812505
000001101.5750006
000001111.5687507
000010001.5625008
000010011.5562509
000010101.550000A
000010111.543750B
000011001.537500C
000011011.531250D
000011101.525000E
000011111.518750F
000100001.5125010
000100011.5062511
000100101.5000012
000100111.4937513
000101001.4875014
000101011.4812515
000101101.4750016
000101111.4687517
000110001.4625018
000110011.4562519
000110101.450001A
000110111.443751B
000111001.437501C
000111011.431251D
000111101.425001E
000111111.418751F
001000001.4125020
001000011.4062521
001000101.4000022
001000111.3937523
001001001.3875024
VID6
400 mV
< 85°C; 10.8 V < VCC < 13.2 V; All DAC Codes; C
J
0.8 V < DAC < 1.0 V
0.5 V < DAC < 0.8 V
With CS Input Vin = 0 V−19mV
VID5
200 mV
VID4
100 mV
VID3
50 mV
VID2
25 mV
= 0.1 F, unless otherwise stated)
VCC
−−±0.75
VID1
12.5 mV
VID0
6.25 mV
±7.0
±8.0
Nominal
DAC
Voltage (V)
%
mV
mV
HEX
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NCP5388
Table 2: VR11 VID Codes
VID7
800 mV
001001011.3812525
001001101.3750026
001001111.3687527
001010001.3625028
001010011.3562529
001010101.350002A
001010111.343752B
001011001.337502C
001011011.331252D
001011101.325002E
001011111.318752F
001100001.3125030
001100011.3062531
001100101.3000032
001100111.2937533
001101001.2875034
001101011.2812535
001101101.2750036
001101111.2687537
001110001.2625038
001110011.2562539
001110101.250003A
001110111.243753B
001111001.237503C
001111011.231253D
001111101.225003E
001111111.218753F
010000001.2125040
010000011.2062541
010000101.2000042
010000111.1937543
010001001.1875044
010001011.1812545
010001101.1750046
010001111.1687547
010010001.1625048
010010011.1562549
010010101.150004A
010010111.143754B
010011001.137504C
010011011.131254D
010011101.125004E
010011111.118754F
010100001.1125050
010100011.1062551
010100101.1000052
VID6
400 mV
VID5
200 mV
VID4
100 mV
VID3
50 mV
VID2
25 mV
VID1
12.5 mV
VID0
6.25 mV
DAC
Voltage (V)
HEXNominal
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NCP5388
Table 2: VR11 VID Codes
VID7
800 mV
010100111.0937553
010101001.0875054
010101011.0812555
010101101.0750056
010101111.0687557
010110001.0625058
010110011.0562559
010110101.050005A
010110111.043755B
010111001.037505C
010111011.031255D
010111101.025005E
010111111.018755F
011000001.0125060
011000011.0062561
011000101.0000062
011000110.9937563
011001000.9875064
011001010.9812565
011001100.9750066
011001110.9687567
011010000.9625068
011010010.9562569
011010100.950006A
011010110.943756B
011011000.937506C
011011010.931256D
011011100.925006E
011011110.918756F
011100000.9125070
011100010.9062571
011100100.9000072
011100110.8937573
011101000.8875074
011101010.8812575
011101100.8750076
011101110.8687577
011110000.8625078
011110010.8562579
011110100.850007A
011110110.843757B
011111000.837507C
011111010.831257D
011111100.825007E
011111110.818757F
100000000.8125080
VID6
400 mV
VID5
200 mV
VID4
100 mV
VID3
50 mV
VID2
25 mV
VID1
12.5 mV
VID0
6.25 mV
DAC
Voltage (V)
HEXNominal
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NCP5388
Table 2: VR11 VID Codes
VID7
800 mV
100000010.8062581
100000100.8000082
100000110.7937583
100001000.7875084
100001010.7812585
100001100.7750086
100001110.7687587
100010000.7625088
100010010.7562589
100010100.750008A
100010110.743758B
100011000.737508C
100011010.731258D
100011100.725008E
100011110.718758F
100100000.7125090
100100010.7062591
100100100.7000092
100100110.6937593
100101000.6875094
100101010.6812595
100101100.6750096
100101110.6687597
100110000.6625098
100110010.6562599
100110100.650009A
100110110.643759B
100111000.637509C
100111010.631259D
100111100.625009E
100111110.618759F
101000000.61250A0
101000010.60625A1
101000100.60000A2
101000110.59375A3
101001000.58750A4
101001010.58125A5
101001100.57500A6
101001110.56875A7
101010000.56250A8
101010010.55625A9
101010100.55000AA
101010110.54375AB
101011000.53750AC
101011010.53125AD
101011100.52500AE
VID6
400 mV
VID5
200 mV
VID4
100 mV
VID3
50 mV
VID2
25 mV
VID1
12.5 mV
VID0
6.25 mV
DAC
Voltage (V)
HEXNominal
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NCP5388
Table 2: VR11 VID Codes
VID7
800 mV
101011110.51875AF
101100000.51250B0
101100010.50625B1
101100100.50000B2
11111110OFFFE
11111111OFFFF
VID6
400 mV
VID5
200 mV
VID4
100 mV
VID3
50 mV
VID2
25 mV
VID1
12.5 mV
VID0
6.25 mV
DAC
Voltage (V)
OFFB3 to FD
HEXNominal
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NCP5388
TYPICAL CHARACTERISTICS
13.6
13.4
13.2
13.0
12.8
, IC QUIESCENT CURRENT (mA)
CC
I
12.6
0
10203040
TA, AMBIENT TEMPERATURE (°C)
Figure 5. IC Quiescent Current vs. Ambient
Temperature
0.0198
0.0196
0.0194
0.0192
0.0190
0.0188
DAC OFFSET
0.0186
0.0184
0.0182
0.0180
10
9
8
, UNDERVOLTAGE LOCKOUT
THRESHOLD VOLTAGE (V)
CC
V
506070
7
020 3040506070
Figure 6. VCC Undervoltage Lockout
Threshold Voltage vs. Ambient Temperature
25°C
0°C
70°C
0.6
0.50.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4
VID
VCC Increasing Voltage
VCC Decreasing Voltage
10
TA, AMBIENT TEMPERATURE (°C)
1.5 1.6
Figure 7. Typical DAC Voltage Offset vs.
Temperature
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NCP5388
FUNCTIONAL DESCRIPTION
General
The NCP5388 dual edge modulated multiphase PWM
controller is specifically designed with the necessary
features for a high current VR10 or VR11 CPU power
system. The IC consists of the following blocks: Precision
Programmable DAC, Differential Remote Voltage Sense
Amplifier, High Performance Voltage Error Amplifier,
Differential Current Feedback Amplifiers, Precision
Oscillator and Triangle Wave Generators, and PWM
Comparators. Protection features include Undervoltage
Lockout, Soft−Start, Overcurrent Protection, Overvoltage
Protection, and Power Good Monitor.
Remote Output Sensing Amplifier (RSA)
A true differential amplifier allows the NCP5388 to
measure Vcore voltage feedback with respect to the Vcore
ground reference point by connecting the Vcore reference
point to VS+, and the Vcore ground reference point to VS−.
This configuration keeps ground potential differences
between the local controller ground and the Vcore ground
reference point from affecting regulation of Vcore between
Vcore and Vcore ground reference points. The RSA also
subtracts the DAC (minus VID offset) voltage, thereby
producing an unamplified output error voltage at the
DIFFOUT pin. This output also has a 1.3 V bias voltage to
allow both positive and negative error voltages.
Precision Programmable DAC
A precision programmable DAC is provided. This DAC
has 0.75% accuracy over the entire operating temperature
range of the part. The DAC can be programmed to support
either VR10 or VR11 specifications. A program selection pin
is provided to accomplish this. This pin also sets the startup
mode of operation. Connect this pin to 1.25 V to select the
VR11 DAC table, and the VR11 startup mode. Connect this
pin to ground to select the VR10 DAC table and the VR11
startup mode. Connect this pin to VREF to select the VR10
DAC table and the VR10 startup mode.
High Performance Voltage Error Amplifier
The error amplifier is designed to provide high slew rate
and bandwidth. Although not required when operating as
a voltage regulator for VR10 or VR11, a capacitor from
COMP to VFB is required for stable unity gain test
configurations.
Gate Driver Outputs and 2/3/4 Phase Operation
The part can be configured to run in 2−, 3−, or 4−phase
mode. In 2−phase mode, phases 1 and 3 should be used to
drive the external gate drivers as shown in the 2−phase
Applications Schematic. In 3−phase mode, gate output G4
must be grounded as shown in the 3−phase Applications
Schematic. In 4−phase mode all 4 gate outputs are used as
shown in the 4−phase Applications Schematic. The
following truth table summarizes the modes of operation:
Gate Output Connections
Mode
2−PhaseNormalOPENNormalOPEN
3−PhaseNormalNormalNormalGND
4−PhaseNormalNormalNormalNormal
G1G2G3G4
These are the only allowable connection schemes to
program the modes of operation.
Differential Current Sense Amplifiers
Four differential amplifiers are provided to sense the
output current of each phase. The inputs of each current
sense amplifier must be connected across the current
sensing element of the phase controlled by the
corresponding gate output (G1, G2, G3, or G4). If a phase
is unused, the differential inputs to that phase’s current
sense amplifier must be shorted together and connected
to V
as shown in the 2− and 3−phase Application
CCP
Schematics.
A voltage is generated across the current sense element
(such as an inductor or sense resistor) by the current
flowing in that phase. The output of the current sense
amplifiers are used to control three functions. First, the
output controls the adaptive voltage positioning, where the
output voltage is actively controlled according to the
output current. In this function, all of the current sense
outputs are summed so that the total output current is used
for output voltage positioning. Second, the output signal is
fed to the current limit circuit. This again is the summed
current of all phases in operation. Finally, the individual
phase current is connected to the PWM comparator. In this
way current balance is accomplished.
Oscillator and Triangle Wave Generator
A programmable precision oscillator is provided. The
oscillator ’s frequency is programmed by the resistance
connected from the ROSC pin to ground. The user will
usually form this resistance from two resistors in order to
create a voltage divider that uses the ROSC output voltage
as the reference for creating the current limit setpoint
voltage. The oscillator frequency range is 100 kHz/phase
to 1.0 MHz/phase. The oscillator generates up to 4 triangle
waveforms (symmetrical rising and falling slopes)
between 1.3 V and 2.3 V. The triangle waves have a phase
delay between them such that for 2−, 3−, and 4−phase
operation the PWM outputs are separated by 180, 120, and
90 angular degrees, respectively.
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NCP5388
PWM Comparators with Hysteresis
Four PWM comparators receive the error amplifier
output signal at their noninverting input. Each comparator
receives one of the triangle waves offset by 1.3 V at it’s
inverting input. The output of the comparator generates the
PWM outputs G1, G2, G3, and G4.
During steady state operation, the duty cycle will center
on the valley of the triangle waveform, with steady state
duty cycle calculated by V
. During a transient event,
out/Vin
both high and low comparator output transitions shift phase
to the points where the error amplifier output intersects the
down and up ramp of the triangle wave.
PROTECTION FEATURES
Undervoltage Lockout
An undervoltage lockout (UVLO) senses the VCC input.
During powerup, the input voltage to the controller is
monitored, and the PWM outputs and the soft−start circuit
are disabled until the input voltage exceeds the threshold
voltage of the UVLO comparator. The UVLO comparator
incorporates hysteresis to avoid chattering, since VCC is
likely to decrease as soon as the converter initiates
soft−start.
Overcurrent Shutdown
A programmable overcurrent function is incorporated
within the IC. A comparator and latch makeup this
function. The inverting input of the comparator is
connected to the ILIM pin. The voltage at this pin sets the
maximum output current the converter can produce. The
ROSC pin provides a convenient and accurate reference
voltage from which a resistor divider can create the
overcurrent setpoint voltage. Although not actually
disabled, tying the ILIM pin directly to the ROSC pin sets
the limit above useful levels – effectively disabling
overcurrent shutdown. The comparator noninverting input
is the summed current information from the current sense
amplifiers. The overcurrent latch is set when the current
information exceeds the voltage at the ILIM pin. The
outputs are immediately disabled, the VR_RDY and
DRVON pins are pulled low, and the soft−start is pulled
low. The outputs will remain disabled until the VCC voltage
is removed and re−applied, or the ENABLE input is
brought low and then high.
Overvoltage Protection and Power Good Monitor
An output voltage monitor is incorporated. During
normal operation, if the voltage at the DIFFOUT pin
exceeds 1.3 V, the VR_RDY pin goes low, the DRVON
signal remains high, the PWM outputs are set low. The
outputs will remain disabled until the VCC voltage is
removed and reapplied. During normal operation, if the
output voltage falls more than 300 mV below the DAC
setting, the VR_RDY pin will be set low until the output
rises.
Soft−Start
The NCP5388 incorporates an externally programmable
soft−start. The soft−start circuit works by controlling the
ramp−up of the DAC voltage during powerup. The initial
soft−start pin voltage is 0 V. The soft−start circuitry clamps
the DAC input of the Remote Sense Amplifier to the SS pin
voltage until the SS pin voltage exceeds the DAC setting
minus VID offset. The soft−start pin is pulled to 0 V if there
is an overcurrent shutdown, if the ENABLE pin is low, if
VCC is below the UVLO threshold, or if an overvoltage
condition exists.
There are two possible soft−start modes: Legacy VR10
and VR11. VR10 mode simply ramps Vcore from 0 V
directly to the DAC setting at the rate set by the capacitor
connected to the SS pin. The VR11 mode ramps Vcore to
1.1 V at the SS capacitor charge rate, pauses at 1.1 V for
170 s, reads the VID pins to determine the DAC setting,
then ramps Vcore to the final DAC setting at the
Dynamic VID slew rate of 7.3 mV/s. Typical VR10 and
VR11 soft−start sequences are shown in the following
graphs.
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NCP5388
2.4
2.2
2.0
1.8
1.6
1.4
1.2
VOLTAGE
1.0
0.8
0.6
0.4
0.2
0
0
TIME
Figure 8. Typical VR10 Soft−Start Sequence to Vcore = 1.3 V
2.4
2.2
2.0
1.8
1.6
1.4
1.2
VOLTAGE
1.0
0.8
0.6
0.4
0.2
0
0
Boot Voltage
Boot
Dwell Time
TIME
VID Setting
Vcore Voltage
SS Pin Voltage
VID Setting
NCP5388
Internal Dynamic
VID Rate Limit
Vcore Voltage
SS Pin Voltage
Figure 9. Typical VR11 Soft−Start Sequence to Vcore = 1.3 V
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NCP5388
APPLICATION INFORMATION
The NCP5388 is a high performance multiphase
controller optimized to meet the Intel VR11 Specifications.
The demo board for the NCP5388 is available by request.
It is configured as a four phase solution with decoupling
designed to provide a 1.0 m load line under a 100 A step
load. A schematic is available upon request from ON
Semiconductor.
Startup Procedure
The demo board comes with a Socket 775 and requires
an Intel dynamic load tool (VTT Tool) available through a
third party supplier, Cascade Systems. The web page is
http://www.cascadesystems.net/.
Start by installing the test tool software. It’s best to power
the test tool from a separate ATX power supply. The test
tool should be set to a valid VID code of 0.5 V or above
in−order for the controller to start. Consult the VTT help
manual for more detailed instructions.
Startup Sequence
1. Make sure the VTT software is installed.
2. Powerup the PC or Laptop do not start the VTT
software.
3. Insert the VTT Test Tool adapter into the socket
and lock it down.
4. Inset the socket saver pin field into the bottom of
the VTT test tool.
5. Carefully line up the tool with the socket in the
board and press tool into the board.
6. Connect the scope probe, or DMM to the voltage
sense lines on the test tool. When using a scope
probe it is best to isolate the scope from the AC
ground. Make the ground connection on the scope
probe as short as possible.
7. Connect the first ATX supply to the VTT tool.
8. Powerup the first ATX supply to the VTT tool.
9. Start the VTT tool software in VR11 mode with
the current limit set to 150 A.
10. Using the VTT tool software, select a VID code
that is 0.5 V or above.
11. Connect the second ATX supply to the demo
board.
12. Set the VID DIP switches. All the VID switches
should be up or open.
13. Set the VR_ENABLE DIP switch down or
closed.
14. Set the VR10 DIP switch up or open.
15. Set the VID_SEL switch up or open.
16. Start the second ATX supply by turning it on and
setting the PSON DIP switch low. The green VID
lights should light up to match the VTT tool VID
setting.
17. Set the VR_ENABLE DIP switch up to start the
NCP5388.
18. Check that the output voltage is about 19 mV
below the VID setting.
Step Load Testing
The VTT tool is used to generate the high di/dt step load.
Select the dynamic loading option in the VTT test tool
software. Set the desired step load size, frequency, duty,
and slew rate. See Figures 10 and 11.
Figure 10. Typical Step Load Response
Figure 11. Typical Load Release Event
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NCP5388
Dynamic VID Testing
The VTT tool provides for VID stepping based on the
Intel Requirements. Select the Dynamic VID option.
Before enabling the test set the lowest VID to 0.5 V or
greater and set the highest VID to a value that is greater than
the lowest VID selection, then enable the test. See Figures
12 through 14.
Figure 12. 1.6 to 0.5 Dynamic VID Response
Design Methodology
Decoupling the VCC Pin on the IC
An RC input filter is required as shown in the VCC pin to
minimize supply noise on the IC. The resistor should be sized
such that it does not generate a large voltage drop between the
12 V supply and the IC. See the schematic values.
Understanding Soft−Start
The controller supports two different startup routines. A
legacy VR10 ramp to the initial VID code, or a VR11 Ramp
to the 1.1 V VID code, with a pause to capture the VID code
then resume ramping to target value based on an internal
slew rate limit. See Figures 15 and 16. The controller is
designed to regulate to the voltage on the SS pin until it
reaches the internal DAC voltage. The soft−start cap sets
the initial ramp rate using a typical 5.0 A current. The
typical value to use for the soft−start cap (SS), is typically
set to 0.01 F. This results in a ramp time to 1.1 V of 2.2 ms
based on equation 1.
dt
Css^ i
1.1 · V
2.2 · ms
Css+ 0.01 · F
ss
+
ss
dv
ss
dv
ss
and iss+ 5·A
dt
ss
(eq. 1)
Figure 13. Dynamic VID Settling Time Rising
Figure 14. Dynamic VID Settling Time Falling
Figure 15. VR11 Startup
Figure 16. VR10 Legacy Startup
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NCP5388
Programming the Current Limit and the Oscillator Frequency
The demo board is set for an operating frequency of
approximately 300 kHz. The OSC pin provides a 2.0 V
reference voltage which is divided down with a resistor
divider and fed into the current limit pin ILIM. Calculate
the total series resistance to set the frequency and then
calculate the individual values for current limit divider.
The series resistors RLIM1 and RLIM2 sink current to
ground. This current is internally mirrored into a capacitor
to create an oscillator. The period is proportional to the
resistance and frequency is inversely proportional to the
resistance. The resistance may be estimated by equation 2
or 3 depending on the phase count.
100
90
80
70
60
50
40
ROSC (kOhms)
30
20
10
0
100
200
300
400
500
600
700
32.36 k ^
ROSC +
ROSC +
4 Phase Mode
3 Phase Mode
800
10.14 10
300 · k
4 Phase Mode
10.14 10
Frequency
3 Phase Mode
9.711 10
Frequency
900
1000
9
* 1440
9
* 1440
9
* 1111
(eq. 2)
(eq. 3)
Frequency (kHz)
Figure 17. ROSC vs. Phase Frequency
The current limit function is based on the total sensed
current of all phases multiplied by a gain of 5.94. DCR
sensed inductor current is function of the winding
temperature. The best approach is to set the maximum
Calculate the current limit voltage:
V
ILIMIT
^ 5.94 ·ǒI
MIN_OCP
· DCR
Tmax
)
Solve for the individual resistors:
V
RLIM2 +
Final Equation for the Current Limit Threshold
I
LIMIT(Tinductor
) ^
5.94 · (DCR
ILIMIT·ROSC
2·V
2·V·RLIM2
ǒ
RLIM1)RLIM2
·(1) 0.00393 · C−1(T
25C
Ǔ
) 0.02
The inductors on the demo board have a DCR at 25°C of
0.75 m. Selecting the closest available values of 16.9 k
for RLIM1 and 15.8 k for RLIM2 yield a nominal
operating frequency of 305 kHz and an approximate
current limit of 180 A at 100°C. The total sensed current
can be observed as a scaled voltage at the VDRP pin added
to a positive, no−load offset of approximately 1.3 V.
current limit based on the expected average maximum
temperature of the inductor windings.
DCR
50C
2·Vin·F
Inductor
· Vout
s
−25 · C)))
DCR
(1 ) 0.00393 · C−1(T
Vin−Vout
ǒ
·
RLIM1 + R
*
Tmax
* (N−1) ·
L
Vout
2·Vin·F
+ DCR
OSC−RLIM2
·
s
25C
Vout
Vin−Vout
ǒ
·
Tmax
Ǔ
L
L
−25 · C))
Ǔ
* 0.02
* (N−1) ·
Inductor Selection
When using inductor current sensing it is recommended
that the inductor does not saturate by more than 10% at
maximum load. The inductor also must not go into hard
saturation before current limit trips. The demo board includes
a four phase output filter using the T50−8 core from
Micrometals with 4turns and a DCR target of 0.75 m @
25°C. Smaller DCR values can be used, however, current
sharing accuracy and droop accuracy decrease as DCR
decreases. Use the excel spreadsheet for regulation accuracy
calculations for a specific value of DCR.
(eq. 4)
(eq. 5)
(eq. 6)
Vout
L
(eq. 7)
Ǔ
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NCP5388
Inductor Current Sense Compensation
The NCP5388 uses the inductor current sensing method.
This method uses an RC filter to cancel out the inductance
of the inductor and recover the voltage that is the result of
Rsense(T) +
Figure 18.
0.47 · F · DCR
The demoboard inductor measured 350 nH and 0.75 m
at room temp. The actual value used for Rsense was 953
which matches the equation for Rsense at approximately
50C. Because the inductor value is a function of load and
the current flowing through the inductor’s DCR. This is
done by matching the RC time constant of the current sense
filter to the L/DCR time constant. The first cut approach is
to use a 0.47 F capacitor for C and then solve for R.
L
·(1) 0.00393 · C−1·(T−25 · C))
25C
inductor temperature final selection of R is best done
experimentally on the bench by monitoring the Vdroop pin
and performing a step load test on the actual solution.
It is desirable to keep the Rsense resistor value below
1.0 k whenever possible by increasing the capacitor values
in the inductor compensation network. The bias current
flowing out of the current sense pins is approximately
100 nA. This current flows through the current sense
resistor and creates an offset at the capacitor which will
appear as a load current at the Vdroop pin. A 1.0 k resistor
will keep this offset at the droop pin below 2.5 mV.
Simple Average PSPICE Model
A simple state average model shown in Figure 19 can be
used to determine a stable solution and provide insight into
the control system.
A complex switching model is available by request
which includes a more detailed board parasitic for this
demo board.
Compensation and Output Filter Design
The values shown on the demo board are a good place to
start for any similar output filter solution. The dynamic
performance can then be adjusted by swapping out various
individual components.
If the required output filter and switching frequency are
significantly different, it’s best to use the available PSPICE
models to design the compensation and output filter from
scratch.
The design target for this demo board was 1.0 m out to
2.0 MHz. The phase switching frequency is currently set to
300 kHz. It can easily be seen that the board impedance of
0.75 m between the load and the bulk capacitance has a
large effect on the output filter. In this case the ten 560 F
80
1/(2*PI*CFB1*(RFB1+RFB))
1/(2*PI*CF*RF)
1/(2*PI*(RBRD+ESRBulk)*CBulk)
dB
60
40
20
−20
RF/RFB
0
bulk capacitors have an ESR of 7.0 m. Thus the bulk ESR
plus the board impedance is 0.7 m + 0.75 m or
1.45 m. The actual output filter impedance does not drop
to 1.0 m until the ceramic breaks in at over 375 kHz. The
controller must provide some loop gain slightly less than
one out to a frequency in excess 300 kHz. At frequencies
below where the bulk capacitance ESR breaks with the
bulk capacitance, the DC−DC converter must have
sufficiently high gain to control the output impedance
completely. Standard Type−3 compensation works well
with the NCP5388. RFB1 should be kept above 50 for
amplifier stability reasons.
The goal is to compensate the system such that the
resulting gain generates constant output impedance from
DC up to the frequency where the ceramic takes over
holding the impedance below 1.0 m. See the example of
the locations of the poles and zeros that were set to optimize
the model above.
Zout Open Loop
Zout Closed Loop
Open Loop Gain with Current loop Closed
Voltage Loop Compensation Gain
1/(2*PI*RF*CF)
RF/RFB1
Error Amp
Open Loop
Gain
−40
−60
−80
1mOhm
1/(2*PI*SQRT(ESL_Cer*CCer))
1/(2*PI*CCer*(RBRD+ESRBulk))
−100
100100010000100000100000010000000
Frequency
Figure 20.
By matching the following equations a good set of starting compensation values can be found for a typical mixed bulk
and ceramic capacitor type output filter.
1
2 ·CF·RF
2 ·CFBI·(RFBI) RFB)
+
2 · (RBRD ) ESRBulk) · CBulk
1
http://onsemi.com
1
+
2 · CCer * (RBRD ) ESRBulk)
31
1
(eq. 9)
Page 32
NCP5388
RFB is always set to 1.0 k and RFB1 is usually set to
100 for maximum phase boost. The value of RF is
typically set to 4.0 k.
Droop Injection and Thermal Compensation
The VDRP signal is generated by summing the sensed
output currents for each phase and applying a gain of
approximately six. VDRP is externally summed into the
feedback network by the resistor RDRP. This induces an
RRDP determines the target output impedance by the
basic equation:
Vout
+ Zout +
Iout
RDRP +
The value of the inductor’s DCR varies with temperature
according to the following equation 10:
offset which is proportional to the output current thereby
forcing the controlled resistive output impedance.
DCR
The system can be thermally compensated to cancel this
effect out to a great degree by adding an NTC (negative
temperature coefficient resistor) in parallel with RFB to
reduce the droop gain as the temperature increases. The
NTC device is nonlinear. Putting a resistor in series with the
Tmax
+ DCR
·(1) 0.00393 · C−1(T
25C
NTC helps make the device appear more linear with
temperature. The series resistor is split and inserted on both
sides of the NTC to reduce noise injection into the feedback
loop. The recommended value for RISO1 and RISO2 is
approximately 1.0 k.
Tmax
−25 · C))
The output impedance varies with inductor temperature by the equation:
Zout(T) +
RFB · DCR
·(1) 0.00393 · C−1(T
25C
Rdroop
−25C)) · 5.94
max
By including the NTC RT2 and the series isolation resistors the new equation becomes:
Zout(T) +
RFB · (RISO1)RT2(T))RISO2)
RFB)RISO1)RT2(T))RISO2
· DCR
·(1) 0.00393 · C−1(T
25C
Rdroop
RFB · DCR · 5.94
RDRP
RFB · DCR · 5.94
Zout
−25C)) · 5.94
max
(eq.
10)
(eq. 11)
(eq. 12)
(eq. 13)
The typical equation of a NTC is based on a curve fit
equation 13.
RT2(T) + RT2
25C
·e
ƪǒ
1
273 )T
1
298
Ǔ
ƫ
(eq. 14)
ǒ
Ǔ
*
The demo board is populated with a 10 k NTC with a
Beta of 4300. Figure 21 shows the uncompensated and
compensated output impedance versus temperature.
Figure 21. Uncompensated and Compensated Output
Impedance vs. Temperature
ON Semiconductor provides an excel spreadsheet to
help with the selection of the NTC. The actual selection of
the NTC will be effected by the location of the output
inductor with respect to the NTC and airflow, and should
be verified with an actual system thermal solution.
VRHOT and VRFAN
Thermal monitoring provides two threshold sensitive
comparators for thermal monitoring. The circuit consists of
two comparators that compare the voltage on the NTC pin
to an internal resistor divider connected to VREF. By
powering the external temperature sense divider with
VREF the tolerance of the VREF voltage is canceled out.
The data sheet specifications for the thresholds are shown
as ratios with respect to VREF.
VR_FAN Upper Threshold Ratio = 0.3625
VR_FAN Lower Threshold Ratio = 0.3025
VR_HOT Upper Threshold Ratio = 0.2815
VR_HOT Lower Threshold Ratio = 0.2190
The following equations can be used to find the
temperature trip points.
RT1(T) + RT1
Ratio
NTC
(T) :
25C
RNTC1 )RNTC2 ) RT1(T)
273 )T
RNTC2 ) RT1(T)
1
ƪǒ
·e
1
298
Ǔ
ƫ
(eq. 15)
(eq. 16)
ǒ
Ǔ
*
The demo board contains a 68 K NTC for RT1 with a
Beta of 4750. RNTC1 is populated with 15 k and RNTC2
is populated with a zero ohm resistor. Figure 22 is a plot of
equation 15. The horizontal trip thresholds intersect the
Ratio
NTC
curve.
http://onsemi.com
32
Page 33
NCP5388
Figure 22.
OVP
The overvoltage protection threshold is not adjustable.
OVP protection is enabled as soon as soft−start begins and
is disabled when the part is disabled. When OVP is tripped,
the controller commands all four gate drivers to enable
their low side MOSFETs, and VR_RDY transitions low. In
order to recover from an OVP condition, VCC must fall
below the UVLO threshold. See the state diagram for
further details. The OVP circuit monitors the output of
DIFFOUT. If the DIFFOUT signal reaches 180 mV above
the nominal 1.3 V offset the OVP will trip. The DIFFOUT
signal is the difference between the output voltage and the
DAC voltage plus the 1.3 V internal offset. This results in
the OVP tracking the DAC voltage even during a dynamic
change in the VID setting during operation.
Gate Driver and MOSFET Selection
ON Semiconductor provides the companion gate driver
IC (NCP3418B). The NCP3418B driver is optimized to
work with a range of MOSFETs commonly used in CPU
applications. The NCP3418B provides special
functionality and is required for the high performance
dynamic VID operation of the part. Contact your local
ON Semiconductor applications engineer for MOSFET
recommendations.
Board Stack−Up
The demo board follows the recommended Intel
Stack−up and copper thickness as shown.
Figure 23.
Board Layout
A complete Allegro ATX and BTX demo board layout
file and schematics are available by request at
www.onsemi.com and can be viewed using the Allegro
Free Physical Viewer 15.x from the Cadence website
http://www.cadence.com/.
http://onsemi.com
Close attention should be paid to the routing of the sense
traces and control lines that propagate away from the
controller IC. Routing should follow the demo board
example. For further information or layout review contact
ON Semiconductor.
33
Page 34
2 X
a
LOCATION
0.15 C
2 X
PIN ONE
0.15 C
D
TOP VIEW
NCP5388
PACKAGE DIMENSIONS
40 PIN QFN, 7x7
MN SUFFIX
CASE 488AG−01
ISSUE O
A
B
E
NOTES:
1. DIMENSIONS AND TOLERANCING PER
ASME Y14.5M, 1994.
2. CONTROLLING DIMENSIONS: MILLIMETER.
3. DIMENSION b APPLIES TO PLATED
TERMINAL AND IS MEASURED BETWEEN
0.25 AND 0.30 MM TERMINAL
4. COPLANARITY APPLIES TO THE EXPOSED
PAD AS WELL AS THE TERMINALS.
MILLIMETERS
DIM MINMAX
A0.801.00
A1 0.000.05
A30.20 REF
b0.180.30
D7.00 BSC
D2 5.505.70
E7.00 BSC
e0.50 BSC
L0.300.50
k0.20−−−
5.70E25.50
0.10 C
(A3)
A
40 X
0.08 C
SEATING PLANE
L
40 X
SIDE VIEW
A1
C
D2
11
10
20
EXPOSED PAD
k
40 X
21
E2
40 X
1
40
b
30
31
e
A0.10BC
0.05 C
BOTTOM VIEW
Pentium is a registered trademark of Intel Corporation.
ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice
to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any
liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental
damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over
time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under
its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body,
or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death
may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees,
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personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part.
SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
LITERATURE FULFILLMENT:
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Phone: 303−675−2175 or 800−344−3860 Toll Free USA/Canada
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Phone: 421 33 790 2910
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Phone: 81−3−5773−3850
http://onsemi.com
34
ON Semiconductor Website: www.onsemi.com
Order Literature: http://www.onsemi.com/orderlit
For additional information, please contact your loc
Sales Representative
NCP5388/D
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