APPLICATION NOTE
HIP6006/7EVAL1
DC-DC Converters for Microprocessors with Fixed Core Voltage Requirements
AN9722
Rev.0.00
Apr 1997
Introduction
Today’s high-performance microprocessors present many
challenges to their power source. High power consumption,
low bus voltages, and fast load changes are the principal
characteristics which have led to the need for a switch-mode
DC-DC converter local to the microprocessor.
Intel has specified Voltage Regulator Modules (VRMs) for
the Pentium Pro and Pentium II microprocessors [1]. These
specifications detail the requirements imposed upon the
input power source(s) by the Pentium Pro and Pentium II
and provide the computer industry with standard DC-DC
converter solutions. A common requirement of these and
similar processors are decreasing supply voltages as the
processor clock frequency increases.
The Intersil HIP6002-5 pulse-width modulator (PWM)
controllers are targeted specifically for DC-DC converters
powering the Pentium Pro, Pentium II, and other high-
performance microprocessors with varying core voltage
requirements. The HIP6002 and HIP6003 have a 4-bit digital
to analog converter (DAC) and the HIP6004-5 have a 5-bit
DAC to address the ‘moving target’ processor core voltage.
The HIP6006 and HIP6007 use the same basic architecture
of the HIP6002-5, but have a reduced feature set. One
feature removed is the DAC, which allows the HIP6006 and
HIP6007 to be packaged in a smaller 14 lead SOIC. These
chips provide cost-effective solutions for point-of-use switch-
mode. DC-DC converters for many applications. This
application note details the HIP6006 and HIP6007 in DC-DC
converters for high-performance microprocessors with a
fixed core voltage.
V
CC
OCSET
SS
RT
MONITOR AND
PROTECTION
OSC
HIP6006
REF
+
-
COMP
-
+
EN
BOOT
UGATE
PHASE
PVCC
LGATE
PGND
GND
NOT PRESENT
(PINS NC)
ON HIP6007
Intersil HIP6006 and HIP6007
The Intersil HIP6006 and HIP6007 are voltage-mode
controllers with many functions needed for high-performance
processors. Figure 1 shows a simple block diagram of the
HIP6006 and HIP6007. Each contains a high-performance
error amplifier, a high-accuracy reference, a programmable
free-running oscillator, and overcurrent protection circuitry.
The HIP6006 has two MOSFET drivers for use in
synchronous-rectified Buck converters. The HIP6007 omits
the lower MOSFET driver for standard Buck configurations.
A more complete description of the parts can be found in
their data sheets [2, 3].
HIP6006/7 Reference Designs
The HIP6006/7EVAL1 is an evaluation board which
highlights the operation of the HIP6006 or the HIP6007 in an
embedded motherboard application. The evaluation board
can be configured as either a synchronous Buck
(HIP6006EVAL1) or standard Buck (HIP6007EVAL1)
converter.
HIP6006EVAL1
The HIP6006EVAL1 is a synchronous Buck converter
capable of providing up to 9A of current at a fixed 2.5V
output voltages. Simple resistor value changes allow for
outputs as low as 1.3V. The schematic and bill-of-materials
for this design can be found in the appendix.
Efficiency
Figure 2 displays the HIP6006EVAL1 efficiency versus load
current for both 5V and 12V inputs with 100 linear feet per
minute (LFM) of airflow. For a given output voltage and load,
the efficiency is lower at higher input voltages. This is due
primarily to higher MOSFET switching losses and is
displayed in Figure 2.
FB
FIGURE 1. BLOCK DIAGRAM OF HIP6006 AND HIP6007
AN9722 Rev.0.00
Apr 1997
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HIP6006/7EVAL1
DC-DC Converters for
Microprocessors with Fixed Core
Transient Response
90
V
IN
= 5V
EFFICIENCY (%)
Figure 3 shows a laboratory oscillogram of the HIP6006EVAL1
in response to a 0-9A load transient application. The output
voltage responds rapidly and is within 1% of its nominal value
in less than 15s.
85
V
IN
= 12V
80
Output Voltage Ripple
The output voltage ripple and inductor current of the
HIP6006EVAL1 is shown in Figure 4. The input voltage is 5V
and the load current is 9A for this oscillogram. Peak-to-peak
voltage ripple is about 20mV under these conditions.
75
HIP6007EVAL1
2
4
6
LOAD CURRENT (A)
8
10
FIGURE 2. HIP6006EVAL1 EFFICIENCY vs LOAD
The HIP6007EVAL1 is a standard Buck converter capable of
providing up to 9A of current. The schematic and bill-of-
materials for this design can be found in the appendix. The
HIP6007EVAL1 differs from the HIP6006EVAL1 in four ways:
1. U1 is a HIP6007
2. CR3 replaces Q2 and CR2
3. Jumper JP1 is added
2.50V
V
OUT
50mV/DIV
COMP
2V/DIV
4. L1 is a larger inductor
JP1 is needed because CR3 is a dual, common-cathode
device and it is replacing a MOSFET. JP1 connects one
device’s anode (the MOSFET gate in the HIP6006EVAL1) to
ground. The other anode and the common cathode replace the
MOSFET source and drain respectively.
0V
I
L
5A/DIV
0A
Efficiency
Figure 5 shows the efficiency data for the HIP6007EVAL1
under identical conditions as Figure 2 for the HIP6006EVAL1.
Comparing the two graphs reveals that the Synchronous-Buck
design is a little more efficient than the Standard-Buck design
over most of the load range.
TIME (10ms/DIV)
FIGURE 3. HIP6006EVAL1 TRANSIENT RESPONSE
WITH V
IN
= 12V
Transient Response
Figure 6 shows a laboratory oscillogram of the HIP6007EVAL1
in response to a 0-9A load transient application. The output
voltage responds a little slower than the HIP6006EVAL1, but
still is within 1% of its nominal value in less than 25ms. Since
the HIP6007EVAL1 uses a larger output inductor and identical
control loop compensation (R3, R5, C14, and C15), the closed-
loop gain crossover frequency is lower than for the
HIP6006EVAL1. Check the Feedback Compensation section
of either data sheet for details on loop compensation design.
Table 1 details simulated closed-loop bandwidth and phase
margin for both reference boards at both +5V and +12V input
sources.
TABLE 1. CONTROL LOOP CHARACTERISTICS
HIP6006EVAL1
HIP6007EVAL1
V
IN
= 5V
12KHz
68
o
V
IN
= 12V
28KHz
71
o
V
OUT
20mV/DIV
I
L
1A/DIV
TIME (1ms/DIV)
V
IN
= 5V
f
0dB
MARGIN
27KHz
72
o
V
IN
= 12V
61KHz
62
o
FIGURE 4. HIP6006EVAL1 OUTPUT VOLTAGE RIPPLE
AN9722 Rev.0.00
Apr 1997
Page 2 of 9
HIP6006/7EVAL1
DC-DC Converters for
Microprocessors with Fixed Core
OC Protection
90
V
IN
= 5V
EFFICIENCY (%)
85
V
IN
= 12V
80
75
Both the HIP6006EVAL1 and HIP6007EVAL1 have lossless
overcurrent (OC) protection. This is accomplished via the
current-sense function of the HIP600x family. The HIP6006
and HIP6007 sense converter load current by monitoring the
drop across the upper MOSFET (Q1 in the schematics). By
selecting the appropriate value of the OCSET resistor (R6), an
overcurrent protection scheme is employed without the cost
and power loss associated with an external current-sense
resistor. See the
Over-Current Protection
section of either the
HIP6006 and HIP6007 data sheet for details on the design
procedure for the OCSET resistor.
8
10
2
4
6
LOAD CURRENT (A)
Customization of Reference Designs
The HIP6006EVAL1 and HIP6007EVAL1 reference designs
are solutions for Pentium-class microprocessors with current
demands of up to 9A. The two designs share much common
circuitry and the same printed circuit board. Other than the four
items listed under the
HIP6007EVAL1
section, one basic
design is employed to meet many different applications. The
evaluation boards can be powered from +5V or +12V and a
standard Buck or a synchronous Buck topology may be
employed. Employing one basic design for numerous
applications involves some trade-offs. These trade-offs are
discussed below to help the user optimize for a given
application.
FIGURE 5. HIP6007EVAL1 EFFICIENCY vs LOAD
V
OUT
50mV/DIV
2.50V
COMP
2V/DIV
0V
I
L
5A/DIV
0A
Control Loop Bandwidth/Transient Response
TIME (10ms/DIV)
FIGURE 6. HIP6007EVAL1 TRANSIENT RESPONSE
WITH V
IN
= 12V
V
OUT
20mV/DIV
I
L
1A/DIV
Table 1 shows how the control loop characteristics vary with
line voltage and topology. The line voltage determines the
amount of DC gain, which directly affects the modulator
(control-to-output) transfer function. The topology (standard
buck or synchronous buck) is important because we have
chosen to use a larger output inductor for the standard buck
(HIP6005) design. This lowers the boundary of continuous
conduction mode (ccm) and discontinuous conduction mode
(dcm) operation. Staying in ccm at light loads can have an
adverse affect on transient response of the converter. The
HIP6006EVAL1 design will not go into dcm operation because
the lower MOSFET conducts current even at light or zero load
conditions.
From Table 1, we see that the highest control loop bandwidth is
the HIP6006EVAL1 with V
IN
= 12V. The transient response of
the converter for this case is shown in Figure 3. The other
three cases have slower responding loops and can be
improved with value changes in the compensation
components. Table 2 details suggested changes and the
improved control loop characteristics for the three applications
with slower control loops.
TIME (1s/DIV)
FIGURE 7. HIP6007EVAL1 OUTPUT VOLTAGE RIPPLE
Output Voltage Ripple
The output voltage ripple and inductor current of the
HIP6007EVAL1 is shown in Figure 7. The input voltage is 5V
and the load current is 9A for this oscillogram. Peak-to-peak
voltage ripple is less than that for the HIP6006EVAL1 (about
15mV), since the output inductor is larger.
AN9722 Rev.0.00
Apr 1997
Page 3 of 9
HIP6006/7EVAL1
TABLE 2. MODIFICATIONS TO CONTROL LOOP
HIP6006EVAL1
V
IN
= 5V
R5
C14
f
0dB
MARGIN
30.1K
no change
47kHz
53
o
V
IN
= 12V
no change
no change
61kHz
62
o
HIP6007EVAL1
V
IN
= 5V
80.6K
10p
44kHz
40
o
V
IN
= 12V
30.1K
no change
48kHz
52
o
90
DC-DC Converters for
Microprocessors with Fixed Core
RFP25N05 (used on the HIP6006/7EVAL1) has a r
DS(ON)
equal to 47m (maximum at 25
o
C) versus 28m for the
RFP45N06. In comparison to the RFP25N05, the RFP45N06
MOSFETs increased switching losses are greater than its
decreased conduction losses at load currents up to about 7A
with a 5V input and about 9A with a 12V input.
V
IN
= 5V, RFP25N05
V
IN
= 5V, RFP45N06
Ripple Voltage
The amount of ripple voltage on the output of the DC-DC
converter varies with input voltage, switching frequency, output
inductor, and output capacitors. For a fixed switching
frequency and output filter, the voltage ripple increases with
higher input voltage. The ripple content of the output voltage
can be estimated with the following simple equation:
V
OUT
=
I
L
ESR
EFFICIENCY (%)
85
80
V
IN
= 12V, RFP25N05
V
IN
= 12V, RFP45N06
75
where
V
OUT
V
IN
–
V
OUT
---------------
Ts
-
V
IN
I
L
= -----------------------------------------------------------------------
L
OUT
2
4
6
LOAD CURRENT (A)
8
10
FIGURE 8. HIP6006EVAL1 EFFICIENCY WITH EITHER
RFP25N05 MOSFETs OR RFP45N06 MOSFETs
ESR = equivalent series resistance of output capacitors
Ts = switching period (1/Fs)
L
OUT
= output inductance
Therefore, for equivalent output ripple performance at V
IN
=
12V as at 5V, the output filter or switching frequency must
change. Assuming 200KHz operation is desired, either the
output inductor value should increase or the number of parallel
output capacitors should increase (to decrease the effective
ESR).
Conclusion
The HIP6006EVAL1 and HIP6007EVAL1 are DC-DC
converters reference designs for microprocessors with fixed
core voltages and current requirements of up to 9A. In addition,
the designs can be modified for applications with different
requirements. The printed circuit board is laid out to
accommodate the necessary components for operation at
currents up to 15A.
References
For Intersil documents available on the web, see
http://www.intersil.com/
[1]
Pentium-Pro Processor Power Distribution Guidelines,
Intel Application Note AP-523, November, 1995.
[2]
HIP6006 Data Sheet,
Intersil Corporation, Doc. No. 4306.
[3]
HIP6007 Data Sheet,
Intersil Corporation, Doc. No. 4307.
Increased Output Power Capability
The HIP6006/7EVAL1 printed circuit board is laid out with
flexibility to increase the power level of the DC-DC converter
beyond 9A. Locations for additional input capacitors and output
capacitors are provided. In conjunction with higher current
MOSFETs, Schottky rectifiers, and inductors, the evaluation
board can be tailored for applications requiring upwards of
15A. The HIP6006 and HIP6007 data sheets’ Component
Selection Guidelines sections help the user with the design
issues for these applications. Of course, the HIP6006/7EVAL1
can be modified for more cost-effective solutions at lower
currents as well.
MOSFET Selection
As a supplement to the data sheets’ application information on
MOSFET Selection Considerations, this section shows
graphically that a larger, lower r
DS(ON)
MOSFET does not
always improve converter efficiency. Figure 8 shows that
smaller RFP25N05 MOSFETs are more efficient over most of
the line and load range than larger RFP45N06 MOSFETs. The
AN9722 Rev.0.00
Apr 1997
Page 4 of 9
HIP6006/7EVAL1
12V
CC
V
IN
C1-3
3 x 680F
RTN
DC-DC Converters for
Microprocessors with Fixed Core
C17-18
2 x 1F
1206
R7
10K
ENABLE
C12
1F
1206
EN 6
SS 3
RT 1
C19
V
CC
14
MONITOR AND
PROTECTION
2 OCSET
10 BOOT
9 UGATE
U1
8 PHASE
13 PVCC
+
-
4
33pF
R5
15K
R4
SPARE
-
+
7
GND
JP1
12 LGATE
11 PGND
Q2
CR2
MBR
340
C6-9
4 x 1000F
RTN
Q1
C20
0.1F
1000pF
R6
3.01k
CR1
4148
PHASE
TP2
C13
0.1F
OSC
R1
SPARE
REF
HIP6006
L1
V
OUT
FB 5
R2
1K
C14
C15
0.01F
C16
R3
1K
SPARE
COMP
COMP
TP1
FIGURE 9. HIP6006EVAL1 SCHEMATIC
12V
CC
V
IN
C1-3
3 x 680F
RTN
C17-18
2 x 1F
1206
R7
10K
ENABLE
C12
1F
1206
EN 6
SS 3
RT 1
C19
V
CC
14
MONITOR AND
PROTECTION
2 OCSET
10 BOOT
Q1
9 UGATE
U1
8 PHASE
13 NC
+
-
-
+
4
COMP
R5
15K
7
12 NC
11 NC
GND
JP1
CR3
C6-9
4 x 1000F
RTN
C20
0.1F
1000pF
R6
3.01k
CR1
4148
PHASE
TP2
C13
0.1F
OSC
R1
SPARE
REF
HIP6007
L
1
V
OUT
FB 5
R2
1K
C14
33pF
C15
0.01F
C16
R3
1K
SPARE
R4
SPARE
COMP
TP1
FIGURE 10. HIP6007EVAL1 SCHEMATIC
AN9722 Rev.0.00
Apr 1997
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