High Efficiency Power Supply for Intel IMVP-6/IMVP-6+/IMVP-6.5 CPUs

High Efficiency Power Supply for Intel
IMVP-6/IMVP-6+/IMVP-6.5 CPUs
Jian Li and Gina Le
The LTC3816 is a single-phase synchronous step-down DC/DC switching regulator
controller that complies with Intel Mobile Voltage Positioning (IMVP)-6/6+/6.5 specifications.
It uses a constant-frequency voltage mode architecture with a leading edge modulation
topology, allowing extremely low output voltages and very fast load transient response.
The LTC3816 satisfies all of the IMVP-6, IMVP-6+ and IMVP-6.5 requirements, including
7-bit VID code, start-up to a preset boot voltage, differential remote output voltage sensing
with programmable active voltage positioning (AVP), IMON output current reporting, power
optimization during sleep state and fast or slow slew rate sleep state exit. It is suitable for a
wide range of input voltages from 4.5V to 36V and output voltages up to 1.5V. The LTC3816
is available in 38-pin thermally enhanced eTSSOP and 5mm × 7mm QFN packages.
Figure 1. An IMVP-6.5 converter using
temperature-compensated inductor
DCR sensing
10k
14k
8.25k
ISENN
15nF
15nF
5.1k
21k
ITCFB
IMAX
ITC
ISENP
RPTC
1000pF
VRON
LFF
PREIMON
IMON
IMON
LTC3816
VRON
22pF
2.2nF
470pF
22pF
VID0
VID1
VID2
VID3
VID4
VID5
VID6
COMP
VIN
EXTVCC
SS
INTVCC
DPRSLPVR
20 | October 2011 : LT Journal of Analog Innovation
BG
VID0
BSOURCE
MODE/SYNC
RFREQ
VID1
VID6
VID2
VID5
VID3
PWRGD 1.9k
1.1V
3.3V
GND
VID4
VIN
4.5V TO 24V
+
NTC
0.1µF
BOOST
VFB
CSLEW
CLKEN# 1.9k
CLKEN#
TG
SERVO
10pF
56Ω
2.55k
SW
VCC(SEN)
12k
0.1µF
VRTT#
VRTT#
PWRGD
VSS(SEN)
10k
6.98k
DB
5V
QT
100Ω
CVIN
100Ω
L
+
QB
PTC
CBULK
CCER
4.7µF
CBULK: 3 × SANYO 2TPF330M6 (330µF)
CCER: 20 × 10µF + 2 × 1µF
CIN: 2 × SANYO OS-CON 35SVPD47M + 2 × 10µF
DB: CMDSH-4E
L: IHLP-5050CE-01 (0.33µH, DCR = 1.3mΩ)
NTC: MURATA NCP18XH103
PTC: MURATA PRF18BC471QB1RB
QB: 2 × RENESAS RJK0330DPB
QT: RENESAS RJK0305DPB
VCC(CORE)
ILOAD(MAX) = 27A
design features
The LTC3816 meets all of Intel’s IMVP-6, IMVP-6+ and IMVP-6.5 specifications in a small
5mm × 7mm 38-pin QFN. With strong gate drivers and short dead-time, the LTC3816
offers high efficiency solutions over a wide input voltage range. Its leading edge modulation
topology allows very small duty cycle operation and ultrafast transient response.
0.78
100
MEASURED RESULT
VCC_CORE(DC MAX)
VCC_CORE(DC MIN)
0.76
80
EFFICIENCY (%)
VOUT (V)
0.74
0.72
0.7
INTEL’S SPEC
0.68
70
60
50
40
30
20
0.66
0.64
PULSE SKIPPING MODE
fSW = 400kHz
90
VOUT = 0.9V
VOUT = 1.2V
VOUT = 1.5V
10
0
5
10
15
20
25
30
0
0
10
1
ILOAD (A)
100
ILOAD (A)
Figure 2. Load regulation with -3mV/A slope
Figure 3. Efficiency with 12V input
AN IMVP-6.5 CONVERTER WITH
4.5V~24V INPUT AND 27A OUTPUT
dead-time, the LTC3816 offers a highly
efficienct solution, as shown in Figure 3.
Figure 1 shows an IMVP-6.5 application
using temperature-compensated inductor DCR sensing. The output voltage is
programmed by a 7-bit VID code. With
temperature-compensated inductor
DCR sensing, the LTC3816 provides an
accurate –3mV/A AVP slope over temperature as shown in Figure 2. With
strong integrated FET drivers and short
The LTC3816’s leading edge modulation topology allows ultrafast transient
response to meet Intel’s stringent requirements. As shown in Figure 4, no undershoot other than AVP is observed during
a load step-up test, easily meeting Intel’s
specifications. Moreover, the LTC3816
incorporates a line feedforward function
to compensate for changes in the line
VOUT = 1V
VOUT
50mV/DIV
voltage and to simplify the loop compensation. The LTC3816 feedback loop is
also capable of dynamically changing the
regulator output to different VID DAC voltages as shown in Figure 5. Upon receiving
a new VID code, the LTC3816 regulates to
its new potential with a programmable
slew rate selected to prevent the converter from generating audible noise.
During start-up, the output voltage is
charged to VBOOT first, according to Intel’s
VRON
1V/DIV
VOUT = IOUT • RDROOP
VBOOT
VOUT
1V/DIV
VOUT
200mV/DIV
VOUT = 0.5V
IOUT
20A/DIV
CLKEN
5V/DIV
PWRGD
5V/DIV
20µs/DIV
Figure 4. Transient response with 20A load step
200µs/DIV
Figure 5. Output voltage transition from 0.5V to 1.0V
in dynamic VID mode
2ms/DIV
Figure 6. Start-up test with preset boot voltage 1.1V
October 2011 : LT Journal of Analog Innovation | 21
The LTC3816 includes an onboard current limit circuit, so that the peak inductor
current can be sensed via inductor DCR or a discrete sense resistor. The
LTC3816 current limit architecture allows momentary overcurrent events for a
predefined duration. The LTC3816 also provides input undervoltage lockout,
output overvoltage protection and PWRGD and overtemperature flags.
IMVP specification. As shown in Figure 6,
VBOOT is 1.1V in IMVP-6.5 and 1.2V in
IMVP-6. Once the output voltage reaches
VBOOT, the CLKEN# output goes low and
the output voltage transitions to the
voltage programmed by the VID code.
ISENN
ITCFB
IMAX
ITC
ISENP
IMON
INTVCC
RPTC
VRON
LTC3816
VRON
22pF
6800pF
470pF 22pF
COMP
VIN
EXTVCC
SS
INTVCC
DPRSLPVR
Figure 7. A dual-channel IMVP-6 converter with
44A output using RSENSE sensing configuration
BG
VID0
BSOURCE
MODE/SYNC
RFREQ
VID1
VID6
VID2
VID5
VID3
P
BOOST
VFB
CSLEW
CONCLUSION
CLKEN#
TG
SERVO
10pF
C
SW
VCC(SEN)
12k
V
VRTT#
PWRGD
VSS(SEN)
10k
3k
LFF
PREIMON
The LTC3816 includes an onboard current limit circuit, so that the peak inductor current can be sensed via inductor
DCR or a discrete sense resistor. The
LTC3816 current limit architecture
allows momentary overcurrent events
for a predefined duration. The LTC3816
also provides input undervoltage lockout, output overvoltage protection and
PWRGD and overtemperature flags.
22 | October 2011 : LT Journal of Analog Innovation
2.43k
22pF
Figure 7 demonstrates that for high current applications, multiple LTC3816s can
be paralleled to provide more power.
The current sharing performance is very
good in both static and dynamic operation conditions, as shown in Figure 8.
The LTC3816 meets all of Intel’s IMVP-6,
IMVP-6+ and IMVP-6.5 specifications in
a small 5mm × 7mm 38-pin QFN. With
strong gate drivers and short dead-time,
the LTC3816 offers high efficiency solutions
over a wide input voltage range. Its leading edge modulation topology allows very
small duty cycle operation and ultrafast
transient response. The LTC3816 provides
high efficiency, high power density, and
high reliability solutions for embedded
computing, mobile computers, Internet
devices and navigation displays. n
10.2k
1000pF
GND
VID4
VID6
VID5
VID4
VID3
VID2
VID1
VID0
CBULK: 4 × SANYO 2TPF330M6 (330µF)
CCER: 32 × 10µF + 2 × 1µF
CIN: 3 × SANYO OS-CON 35SVPD47M + 2 × 10µF
DB: CMDSH-4E
L: IHLP-5050CE-01 (0.33µH, DCR = 1.3mΩ)
PTC: MURATA PRF18BC471QB1RB
QT: RENESAS RJK0305DPB
QB: 2 × RENESAS RJK0330DPB
RSENSE: PANASONIC ERJM1WTF1M0U (1mΩ)
5V
design features
The LTC3816 feedback loop is also capable of dynamically changing the
regulator output to different VID DAC voltages. Upon receiving a new VID
code, the LTC3816 regulates to its new potential with a programmable
slew rate selected to prevent the converter from generating audible noise.
VIN
4.5V TO 24V
100Ω
100Ω
2.43k
1000pF
1.1V 3.3V
511Ω
511Ω
56Ω
3k
1000pF
VRTT#
PWRGD
DB
PREIMON
LTC3816
CLKEN#
L
CVIN
+
QB
CBULK
PTC
–
CCER
L
QT
QB
PTC
+
VCC_CORE
ILOAD(MAX) = 54A
4.7µF
DB
VCC(SEN)
TG
0.1µF
SERVO
BOOST
5V
VFB
VIN
EXTVCC
COMP
INTVCC
SS
BG
4.7µF
BSOURCE
MODE/SYNC
RFREQ
DPRSLPVR
VID6
400kHz
SQUARE WAVE
10k
10pF
12k
6800pF
22pF
22pF
470pF
CSLEW
VID0
VID1
VID5
VID4
INTVCC
VSS(SEN)
SW
RSENSE
RSENSE
IMON
RPTC
VRON
PWRGD
+
0.1µF
ITC
VRTT#
QT
22pF
LFF
3.3V
1000pF
ITCFB
IMAX
ISENP
1.9k
CLKEN# 1.9k
ISENN
10.2k
VID2
GND
VID3
VOUT
200mV/DIV
IL1
10A/DIV
Figure 8. Current sharing performance
for a dual-channel IMVP-6 converter
IL2
10A/DIV
20µs/DIV
October 2011 : LT Journal of Analog Innovation | 23