hip6004a

HIP6004A
®
Data Sheet
November 2002
Buck and Synchronous-Rectifier (PWM)
Controller and Output Voltage Monitor
The HIP6004A provides complete control and protection for
a DC-DC converter optimized for high-performance
microprocessor applications. It is designed to drive two
N-Channel MOSFETs in a synchronous-rectified buck
topology. The HIP6004A integrates all of the control, output
adjustment, monitoring and protection functions into a single
package.
The output voltage of the converter is easily adjusted and
precisely regulated. The HIP6004A includes a fully TTLcompatible 5-input digital-to-analog converter (DAC) that
adjusts the output voltage from 2.1VDC to 3.5VDC in 0.1V
increments and from 1.8VDC to 2.05VDC in 0.05V steps.
The precision reference and voltage-mode regulator hold the
selected output voltage to within ±1% over temperature and
line voltage variations.
The HIP6004A provides simple, single feedback loop,
voltage-mode control with fast transient response. It includes
a 200kHz free-running triangle-wave oscillator that is
adjustable from below 50kHz to over 1MHz. The error
amplifier features a 15MHz gain-bandwidth product and
6V/ms slew rate which enables high converter bandwidth for
fast transient performance. The resulting PWM duty ratio
ranges from 0% to 100%.
The HIP6004A monitors the output voltage with a window
comparator that tracks the DAC output and issues a Power
Good signal when the output is within ±10%. The HIP6004A
protects against over-current and over-voltage conditions by
inhibiting PWM operation. Additional built-in over-voltage
protection triggers an external SCR to crowbar the input
supply. The HIP6004A monitors the current by using the
rDS(ON) of the upper MOSFET which eliminates the need for
a current sensing resistor.
Features
• Drives Two N-Channel MOSFETs
• Operates from +5V or +12V Input
• Simple Single-Loop Control Design
- Voltage-Mode PWM Control
• Fast Transient Response
- High-Bandwidth Error Amplifier
- Full 0% to 100% Duty Ratio
• Excellent Output Voltage Regulation
- ±1% Over Line Voltage and Temperature
• TTL-Compatible 5-Bit Digital-to-Analog Output Voltage
Selection
- Wide Range . . . . . . . . . . . . . . . . . . . 1.8VDC to 3.5VDC
- 0.1V Binary Steps. . . . . . . . . . . . . . . 2.1VDC to 3.5VDC
- 0.05V Binary Steps. . . . . . . . . . . . . 1.8VDC to 2.05VDC
• Power-Good Output Voltage Monitor
• Over-Voltage and Over-Current Fault Monitors
- Does Not Require Extra Current Sensing Element,
Uses MOSFET’s rDS(ON)
• Small Converter Size
- Constant Frequency Operation
- 200kHz Free-Running Oscillator Programmable from
50kHz to over 1MHz
Applications
• Power Supply for Pentium®, Pentium Pro, Pentium II,
PowerPC™, K6™, 6X86™ and Alpha™ Microprocessors
• High-Power 5V to 3.xV DC-DC Regulators
• Low-Voltage Distributed Power Supplies
Pinout
HIP6004A
(SOIC)
TOP VIEW
Ordering Information
PART NUMBER
HIP6004ACB
TEMP.
RANGE (oC)
0 to 70
PACKAGE
20 Ld SOIC
PKG.
NO.
M20.3
6X86™ is a trademark of Cyrix Corporation.
Alpha Micro™ is a trademark of Digital Computer Equipment Corporation.
K6™ is a trademark of Advanced Micro Devices, Inc.
Pentium® is a registered trademark of Intel Corporation.
PowerPC™ is a trademark of IBM.
1
FN4417.2
VSEN
1
OCSET
2
19 OVP
SS
3
18 VCC
VID0
4
17 LGATE
VID1
5
16 PGND
VID2
6
15 BOOT
VID3
7
14 UGATE
VID4
8
13 PHASE
COMP
9
12 PGOOD
FB 10
20 RT
11 GND
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2002. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
HIP6004A
Typical Application
+12V
VIN = +5V OR +12V
VCC
PGOOD
OCSET
MONITOR AND
PROTECTION
SS
EN
BOOT
OVP
RT
VID0
VID1
VID2
VID3
VID4
OSC
UGATE
PHASE
HIP6004A
+VOUT
D/A
FB
-
LGATE
+
+
-
PGND
COMP
GND
VSEN
Block Diagram
VCC
VSEN
POWER-ON
RESET (POR)
110%
+
-
PGOOD
90%
+
-
OVERVOLTAGE
115%
10µA
+
-
OVP
SOFTSTART
+
-
OCSET
REFERENCE
200µA
OVERCURRENT
SS
BOOT
UGATE
4V
PHASE
VID0
VID1
VID2
VID3
VID4
TTL D/A
CONVERTER
(DAC)
PWM
COMPARATOR
DACOUT
+
-
+
-
ERROR
AMP
FB
GATE
INHIBIT CONTROL
LOGIC
PWM
LGATE
PGND
COMP
GND
OSCILLATOR
RT
2
HIP6004A
Absolute Maximum Ratings
Thermal Information
Supply Voltage, VVCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+15V
Boot Voltage, VBOOT - VPHASE . . . . . . . . . . . . . . . . . . . . . . . .+15V
Input, Output or I/O Voltage . . . . . . . . . . . GND -0.3V to VCC +0.3V
ESD Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Class 2
Thermal Resistance (Typical, Note 1)
θJA (oC/W)
SOIC Package (Note 1) . . . . . . . . . . . . . . . . . . . . .
65
Maximum Junction Temperature (Plastic Package) 150oC
Maximum Storage Temperature Range . . . . . . . . . -65oC to 150oC
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . . 300oC
(SOIC - Lead Tips Only)
Operating Conditions
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . +12V ±10%
Ambient Temperature Range. . . . . . . . . . . . . . . . . . . . . 0oC to 70oC
Junction Temperature Range . . . . . . . . . . . . . . . . . . . 0oC to 125oC
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.
NOTE:
1. θJA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details..
Electrical Specifications
Recommended Operating Conditions, Unless Otherwise Noted
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNITS
UGATE and LGATE Open
-
5
-
mA
Rising VCC Threshold
VOCSET = 4.5V
-
-
10.4
V
Falling VCC Threshold
VOCSET = 4.5V
8.2
-
-
V
-
1.26
-
V
VCC SUPPLY CURRENT
Nominal Supply
ICC
POWER-ON RESET
Rising VOCSET Threshold
OSCILLATOR
Free Running Frequency
RT = OPEN
185
200
215
kHz
Total Variation
6kΩ < RT to GND < 200kΩ
-15
-
+15
%
-
1.9
-
VP-P
DAC(VID0-VID4) Input Low Voltage
-
-
0.8
V
DAC(VID0-VID4) Input High Voltage
2.0
-
-
V
DACOUT Voltage Accuracy
-1.0
-
+1.0
%
-
88
-
dB
-
15
-
MHz
-
6
-
V/µs
350
500
-
mA
-
5.5
10
Ω
300
450
-
mA
-
3.5
6.5
Ω
-
115
120
%
VOCSET = 4.5VDC
170
200
230
µA
VVSEN = 5.5V, VOVP = 0V
60
-
-
mA
-
10
-
µA
∆VOSC
Ramp Amplitude
RT = Open
REFERENCE and DAC
ERROR AMPLIFIER
DC Gain
Gain-Bandwidth Product
GBW
Slew Rate
SR
COMP = 10pF
GATE DRIVERS
Upper Gate Source
IUGATE
VBOOT - VPHASE = 12V, VUGATE = 6V
Upper Gate Sink
RUGATE
ILGATE = 0.3A
Lower Gate Source
ILGATE
VCC = 12V, VLGATE = 6V
Lower Gate Sink
RLGATE
ILGATE = 0.3A
PROTECTION
Over-Voltage Trip (VVSEN/DACOUT)
OCSET Current Source
IOCSET
OVP Sourcing Current
IOVP
Soft Start Current
ISS
3
HIP6004A
Electrical Specifications
Recommended Operating Conditions, Unless Otherwise Noted (Continued)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNITS
POWER GOOD
Upper Threshold (VVSEN /DACOUT)
VVSEN Rising
106
-
111
%
Lower Threshold (VVSEN /DACOUT)
VVSEN Falling
89
-
94
%
Hysteresis (VVSEN /DACOUT)
Upper and Lower Threshold
-
2
-
%
IPGOOD = -5mA
-
0.5
-
V
PGOOD Voltage Low
VPGOOD
Typical Performance Curves
80
CGATE = 3300pF
70
60
RT PULLUP
TO +12V
CUPPER = CLOWER = CGATE
ICC (mA)
RESISTANCE (kΩ)
1000
100
50
40
CGATE = 1000pF
30
10
20
RT PULLDOWN TO VSS
CGATE = 10pF
10
10
100
SWITCHING FREQUENCY (kHz)
FIGURE 1. RT RESISTANCE vs FREQUENCY
4
1000
0
100
200
300
400
500
600
700
800
900
SWITCHING FREQUENCY (kHz)
FIGURE 2. BIAS SUPPLY CURRENT vs FREQUENCY
1000
HIP6004A
Functional Pin Description
VSEN 1
20 RT
PGOOD (Pin 12)
PGOOD is an open collector output used to indicate the
status of the converter output voltage. This pin is pulled low
when the converter output is not within ±10% of the
DACOUT reference voltage.
OCSET
2
19 OVP
SS
3
18 VCC
VID0
4
17 LGATE
PHASE (Pin 13)
VID1
5
16 PGND
VID2
6
15 BOOT
VID3
7
14 UGATE
VID4
8
13 PHASE
Connect the PHASE pin to the upper MOSFET source. This
pin is used to monitor the voltage drop across the MOSFET
for over-current protection. This pin also provides the return
path for the upper gate drive.
COMP
9
12 PGOOD
FB 10
11 GND
UGATE (Pin 14)
Connect UGATE to the upper MOSFET gate. This pin
provides the gate drive for the upper MOSFET.
VSEN (Pin 1)
BOOT (Pin 15)
This pin is connected to the converters output voltage. The
PGOOD and OVP comparator circuits use this signal to
report output voltage status and for overvoltage protection.
This pin provides bias voltage to the upper MOSFET driver.
A bootstrap circuit may be used to create a BOOT voltage
suitable to drive a standard N-Channel MOSFET.
OCSET (Pin 2)
PGND (Pin 16)
Connect a resistor (ROCSET) from this pin to the drain of the
upper MOSFET. ROCSET, an internal 200µA current source
(IOCS), and the upper MOSFET on-resistance (rDS(ON)) set
the converter over-current (OC) trip point according to the
following equation:
This is the power ground connection. Tie the lower MOSFET
source to this pin.
I OCS • R OCSET
I PEAK = -------------------------------------------r DS ( ON )
LGATE (Pin 17)
Connect LGATE to the lower MOSFET gate. This pin
provides the gate drive for the lower MOSFET.
VCC (Pin 18)
Provide a 12V bias supply for the chip to this pin.
An over-current trip cycles the soft-start function.
SS (Pin 3)
OVP (Pin 19)
Connect a capacitor from this pin to ground. This capacitor,
along with an internal 10µA current source, sets the softstart interval of the converter.
The OVP pin can be used to drive an external SCR in the
event of an overvoltage condition. Output rising 15% more
than the DAC-set voltage triggers a high output on this pin
and disables PWM gate drive circuitry.
VID0-4 (Pins 4-8)
RT (Pin 20)
VID0-4 are the input pins to the 5-bit DAC. The states of
these five pins program the internal voltage reference
(DACOUT). The level of DACOUT sets the converter output
voltage. It also sets the PGOOD and OVP thresholds. Table
1 specifies DACOUT for the 32 combinations of DAC inputs.
This pin provides oscillator switching frequency adjustment.
By placing a resistor (RT) from this pin to GND, the nominal
200kHz switching frequency is increased according to the
following equation:
COMP (Pin 9) and FB (Pin 10)
COMP and FB are the available external pins of the error
amplifier. The FB pin is the inverting input of the error
amplifier and the COMP pin is the error amplifier output.
These pins are used to compensate the voltage-control
feedback loop of the converter.
GND (Pin 11)
Signal ground for the IC. All voltage levels are measured
with respect to this pin.
5
6
5 • 10
Fs ≈ 200kHz + --------------------R T ( kΩ )
(RT to GND)
Conversely, connecting a pull-up resistor (RT) from this pin
to VCC reduces the switching frequency according to the
following equation:
7
4 • 10
Fs ≈ 200kHz – --------------------R T ( kΩ )
(RT to 12V)
HIP6004A
Functional Description
Over-Current Protection
Soft Start
The POR function initiates the soft start sequence. An internal
10µA current source charges an external capacitor (CSS) on
the SS pin to 4V. Soft start clamps the error amplifier output
(COMP pin) and reference input (+ terminal of error amp) to the
SS pin voltage. Figure 3 shows the soft start interval with
CSS = 0.1µF. Initially the clamp on the error amplifier (COMP
pin) controls the converter’s output voltage. At t1 in Figure 3,
the SS voltage reaches the valley of the oscillator’s triangle
wave. The oscillator’s triangular waveform is compared to the
ramping error amplifier voltage. This generates PHASE pulses
of increasing width that charge the output capacitor(s). This
interval of increasing pulse width continues to t2 . With sufficient
output voltage, the clamp on the reference input controls the
output voltage. This is the interval between t2 and t3 in Figure 3.
At t3 the SS voltage exceeds the DACOUT voltage and the
output voltage is in regulation. This method provides a rapid
and controlled output voltage rise. The PGOOD signal toggles
‘high’ when the output voltage (VSEN pin) is within ±5% of
DACOUT. The 2% hysteresis built into the power good
comparators prevents PGOOD oscillation due to nominal
output voltage ripple.
PGOOD
(2V/DIV.)
4V
2V
0V
15A
10A
5A
0A
TIME (20ms/DIV.)
FIGURE 4. OVER-CURRENT OPERATION
The over-current function cycles the soft-start function in a
hiccup mode to provide fault protection. A resistor (ROCSET)
programs the over-current trip level. An internal 200µA current
sink develops a voltage across ROCSET that is referenced to
VIN . When the voltage across the upper MOSFET (also
referenced to VIN) exceeds the voltage across ROCSET , the
over-current function initiates a soft-start sequence. The softstart function discharges CSS with a 10µA current sink and
inhibits PWM operation. The soft-start function recharges CSS ,
and PWM operation resumes with the error amplifier clamped
to the SS voltage. Should an overload occur while recharging
CSS, the soft start function inhibits PWM operation while fully
charging CSS to 4V to complete its cycle. Figure 4 shows this
operation with an overload condition. Note that the inductor
current increases to over 15A during the CSS charging interval
and causes an over-current trip. The converter dissipates very
little power with this method. The measured input power for the
conditions of Figure 4 is 2.5W.
The over-current function will trip at a peak inductor current
(IPEAK) determined by:
0V
I OCSET • R OCSET
I PEAK = --------------------------------------------------r DS ( ON )
SOFT-START
(1V/DIV.)
OUTPUT
VOLTAGE
(1V/DIV.)
0V
0V
t1
SOFT-START
The HIP6004A automatically initializes upon receipt of
power. Special sequencing of the input supplies is not
necessary. The Power-On Reset (POR) function continually
monitors the input supply voltages. The POR monitors the
bias voltage at the VCC pin and the input voltage (VIN) on
the OCSET pin. The level on OCSET is equal to VIN less a
fixed voltage drop (see over-current protection). The POR
function initiates soft start operation after both input supply
voltages exceed their POR thresholds. For operation with a
single +12V power source, VIN and VCC are equivalent and
the +12V power source must exceed the rising VCC
threshold before POR initiates operation.
The over-current function protects the converter from a
shorted output by using the upper MOSFET’s on-resistance,
rDS(ON) to monitor the current. This method enhances the
converter’s efficiency and reduces cost by eliminating a
current sensing resistor.
OUTPUT INDUCTOR
Initialization
t2
t3
TIME (5ms/DIV.)
FIGURE 3. SOFT START INTERVAL
6
where IOCSET is the internal OCSET current source (200µA
typical). The OC trip point varies mainly due to the
MOSFET’s rDS(ON) variations. To avoid over-current
tripping in the normal operating load range, find the ROCSET
resistor from the equation above with:
1. The maximum rDS(ON) at the highest junction
temperature.
2. The minimum IOCSET from the specification table.
3. Determine IPEAK for I PEAK > I OUT ( MAX ) + ( ∆I ) ⁄ 2 ,
where ∆I is the output inductor ripple current.
HIP6004A
For an equation for the ripple current see the section under component guidelines titled ‘Output Inductor Selection’
.
TABLE 1. OUTPUT VOLTAGE PROGRAM
PIN NAME
PIN NAME
VID4
VID3
VID2
VID1
VID0
NOMINAL OUTPUT
VOLTAGE DACOUT
VID4
VID3
VID2
VID1
VID0
NOMINAL OUTPUT
VOLTAGE DACOUT
0
1
1
1
1
0
1
1
1
1
1
0
0
1
1
1
0
0
1
1
1
1
0
2.1
0
1
1
0
1
0
1
1
1
0
1
2.2
0
1
1
0
0
0
1
1
1
0
0
2.3
0
1
0
1
1
0
1
1
0
1
1
2.4
0
1
0
1
0
0
1
1
0
1
0
2.5
0
1
0
0
1
0
1
1
0
0
1
2.6
0
1
0
0
0
0
1
1
0
0
0
2.7
0
0
1
1
1
0
1
0
1
1
1
2.8
0
0
1
1
0
0
1
0
1
1
0
2.9
0
0
1
0
1
1.80
1
0
1
0
1
3.0
0
0
1
0
0
1.85
1
0
1
0
0
3.1
0
0
0
1
1
1.90
1
0
0
1
1
3.2
0
0
0
1
0
1.95
1
0
0
1
0
3.3
0
0
0
0
1
2.00
1
0
0
0
1
3.4
0
0
0
0
0
2.05
1
0
0
0
0
3.5
NOTE: 0 = connected to GND or VSS, 1 = connected to VDD through pull-up resistors.
Output Voltage Program
The output voltage of a HIP6004A converter is
programmed to discrete levels between 1.8VDC and
3.5VDC . The voltage identification (VID) pins program an
internal voltage reference (DACOUT) with a TTLcompatible 5-bit digital-to-analog converter (DAC). The
level of DACOUT also sets the PGOOD and OVP
thresholds. Table 1 specifies the DACOUT voltage for the
32 different combinations of connections on the VID pins.
The output voltage should not be adjusted while the
converter is delivering power. Remove input power before
changing the output voltage. Adjusting the output voltage
during operation could toggle the PGOOD signal and
exercise the overvoltage protection.
All VID pin combinations resulting in a 0V output setting
activate the Power-On Reset function, disable the gate drive
circuitry and output a 0 logic at PGOOD pin.
Application Guidelines
Layout Considerations
As in any high frequency switching converter, layout is very
important. Switching current from one power device to
7
another can generate voltage transients across the
impedances of the interconnecting bond wires and circuit
traces. These interconnecting impedances should be
minimized by using wide, short printed circuit traces. The
critical components should be located as close together as
possible, using ground plane construction or single point
grounding.
VIN
HIP6004A
UGATE
Q1
LO
PHASE
LGATE
CIN
Q2
D2
VOUT
CO
LOAD
A small ceramic capacitor should be placed in parallel with
ROCSET to smooth the voltage across ROCSET in the
presence of switching noise on the input voltage.
PGND
RETURN
FIGURE 5. PRINTED CIRCUIT BOARD POWER AND
GROUND PLANES OR ISLANDS
Figure 5 shows the critical power components of the
converter. To minimize the voltage overshoot the
interconnecting wires indicated by heavy lines should be part
of ground or power plane in a printed circuit board. The
HIP6004A
components shown in Figure 5 should be located as close
together as possible. Please note that the capacitors CIN
and CO each represent numerous physical capacitors.
Locate the HIP6004A within 3 inches of the MOSFETs, Q1
and Q2. The circuit traces for the MOSFETs’ gate and
source connections from the HIP6004A must be sized to
handle up to 1A peak current.
Figure 6 shows the circuit traces that require additional
layout consideration. Use single point and ground plane
construction for the circuits shown. Minimize any leakage
current paths on the SS PIN and locate the capacitor, Css
close to the SS pin because the internal current source is
only 10µA. Provide local VCC decoupling between VCC and
GND pins. Locate the capacitor, CBOOT as close as
practical to the BOOT and PHASE pins.
VIN
DRIVER
OSC
PWM
COMPARATOR
D1
CBOOT
+12V
ZIN
-
+
REFERENCE
ERROR
AMP
DETAILED COMPENSATION COMPONENTS
ZFB
C2
C1
VOUT
ZIN
C3
R2
Q1 LO
Q2
CO
CO
VE/A
R3
R1
COMP
PHASE
VCC
VOUT
ESR
(PARASITIC)
ZFB
LOAD
HIP6004A
PHASE
+
VOUT
SS
DRIVER
-
∆ VOSC
+VIN
BOOT
LO
FB
+
HIP6004A
DACOUT
CVCC
CSS
GND
FIGURE 7. VOLTAGE-MODE BUCK CONVERTER
COMPENSATION DESIGN
FIGURE 6. PRINTED CIRCUIT BOARD SMALL SIGNAL
LAYOUT GUIDELINES
Feedback Compensation
Figure 7 highlights the voltage-mode control loop for a
synchronous-rectified buck converter. The output voltage
(VOUT) is regulated to the Reference voltage level. The error
amplifier (Error Amp) output (VE/A) is compared with the
oscillator (OSC) triangular wave to provide a pulse-width
modulated (PWM) wave with an amplitude of VIN at the
PHASE node. The PWM wave is smoothed by the output
filter (LO and CO).
The modulator transfer function is the small-signal transfer
function of VOUT/VE/A. This function is dominated by a DC
Gain and the output filter (LO and CO), with a double pole
break frequency at FLC and a zero at FESR. The DC Gain of
the modulator is simply the input voltage (VIN) divided by the
peak-to-peak oscillator voltage ∆VOSC .
Modulator Break Frequency Equations
1
F LC = --------------------------------------2π • L O • C O
1
F ESR = ---------------------------------------2π • ESR • C O
The compensation network consists of the error amplifier
(internal to the HIP6004A) and the impedance networks ZIN
and ZFB. The goal of the compensation network is to provide
a closed loop transfer function with the highest 0dB crossing
8
frequency (f0dB) and adequate phase margin. Phase margin
is the difference between the closed loop phase at f0dB and
180 degrees. The equations below relate the compensation
network’s poles, zeros and gain to the components (R1 , R2 ,
R3 , C1 , C2 , and C3) in Figure 7. Use these guidelines for
locating the poles and zeros of the compensation network:
1. Pick Gain (R2/R1) for desired converter bandwidth
2. Place 1ST Zero Below Filter’s Double Pole (~75% FLC)
3. Place 2ND Zero at Filter’s Double Pole
4. Place 1ST Pole at the ESR Zero
5. Place 2ND Pole at Half the Switching Frequency
6. Check Gain against Error Amplifier’s Open-Loop Gain
7. Estimate Phase Margin - Repeat if Necessary
Compensation Break Frequency Equations
1
F Z1 = --------------------------------2π • R 2 • C 1
1
F P1 = ---------------------------------------------------- C1 • C2
2π • R 2 •  ---------------------
 C 1 + C 2
1
F Z2 = ---------------------------------------------------2π • ( R 1 + R 3 ) • C 3
1
F P2 = --------------------------------2π • R 3 • C 3
Figure 8 shows an asymptotic plot of the DC-DC
converter’s gain vs. frequency. The actual Modulator Gain
has a high gain peak due to the high Q factor of the output
filter and is not shown in Figure 8. Using the above
guidelines should give a Compensation Gain similar to the
curve plotted. The open loop error amplifier gain bounds
HIP6004A
the compensation gain. Check the compensation gain at
FP2 with the capabilities of the error amplifier. The Closed
Loop Gain is constructed on the log-log graph of Figure 8
by adding the Modulator Gain (in dB) to the Compensation
Gain (in dB). This is equivalent to multiplying the modulator
transfer function to the compensation transfer function and
plotting the gain.
The compensation gain uses external impedance networks
ZFB and ZIN to provide a stable, high bandwidth (BW)
overall loop. A stable control loop has a gain crossing with
-20dB/decade slope and a phase margin greater than 45
degrees. Include worst case component variations when
determining phase margin.
100
FZ1 FZ2
FP1
FP2
80
OPEN LOOP
ERROR AMP GAIN
GAIN (dB)
60
40
20
20LOG
(R2/R1)
0
20LOG
(VIN/∆VOSC)
MODULATOR
GAIN
-20
COMPENSATION
GAIN
CLOSED LOOP
GAIN
-40
FLC
-60
10
100
1K
FESR
10K
100K
1M
10M
Pentium Pro be composed of at least forty (40) 1µF ceramic
capacitors in the 1206 surface-mount package.
Use only specialized low-ESR capacitors intended for
switching-regulator applications for the bulk capacitors. The
bulk capacitor’s ESR will determine the output ripple voltage
and the initial voltage drop after a high slew-rate transient.
An aluminum electrolytic capacitor’s ESR value is related to
the case size with lower ESR available in larger case sizes.
However, the equivalent series inductance (ESL) of these
capacitors increases with case size and can reduce the
usefulness of the capacitor to high slew-rate transient
loading. Unfortunately, ESL is not a specified parameter.
Work with your capacitor supplier and measure the
capacitor’s impedance with frequency to select a suitable
component. In most cases, multiple electrolytic capacitors of
small case size perform better than a single large case
capacitor.
Output Inductor Selection
The output inductor is selected to meet the output voltage
ripple requirements and minimize the converter’s response
time to the load transient. The inductor value determines the
converter’s ripple current and the ripple voltage is a function
of the ripple current. The ripple voltage and current are
approximated by the following equations:
∆I =
VIN - VOUT
•
VOUT
Fs x L
VIN
∆VOUT = ∆I x ESR
FREQUENCY (Hz)
FIGURE 8. ASYMPTOTIC BODE PLOT OF CONVERTER GAIN
Component Selection Guidelines
Output Capacitor Selection
An output capacitor is required to filter the output and supply
the load transient current. The filtering requirements are a
function of the switching frequency and the ripple current.
The load transient requirements are a function of the slew
rate (di/dt) and the magnitude of the transient load current.
These requirements are generally met with a mix of
capacitors and careful layout.
Modern microprocessors produce transient load rates above
1A/ns. High frequency capacitors initially supply the transient
and slow the current load rate seen by the bulk capacitors.
The bulk filter capacitor values are generally determined by
the ESR (effective series resistance) and voltage rating
requirements rather than actual capacitance requirements.
High frequency decoupling capacitors should be placed as
close to the power pins of the load as physically possible. Be
careful not to add inductance in the circuit board wiring that
could cancel the usefulness of these low inductance
components. Consult with the manufacturer of the load on
specific decoupling requirements. For example, Intel
recommends that the high frequency decoupling for the
9
Increasing the value of inductance reduces the ripple current
and voltage. However, the large inductance values reduce
the converter’s response time to a load transient.
One of the parameters limiting the converter’s response to a
load transient is the time required to change the inductor
current. Given a sufficiently fast control loop design, the
HIP6004A will provide either 0% or 100% duty cycle in
response to a load transient. The response time is the time
required to slew the inductor current from an initial current
value to the transient current level. During this interval the
difference between the inductor current and the transient
current level must be supplied by the output capacitor.
Minimizing the response time can minimize the output
capacitance required.
The response time to a transient is different for the
application of load and the removal of load. The following
equations give the approximate response time interval for
application and removal of a transient load:
tRISE =
L x ITRAN
VIN - VOUT
tFALL =
L x ITRAN
VOUT
where: ITRAN is the transient load current step, tRISE is the
response time to the application of load, and tFALL is the
response time to the removal of load. With a +5V input
source, the worst case response time can be either at the
application or removal of load and dependent upon the
HIP6004A
DACOUT setting. Be sure to check both of these equations
at the minimum and maximum output levels for the worst
case response time. With a +12V input, and output voltage
level equal to DACOUT, tFALL is the longest response time.
temperature rise according to package thermal-resistance
specifications. A separate heatsink may be necessary
depending upon MOSFET power, package type, ambient
temperature and air flow.
Input Capacitor Selection
PUPPER = Io2 x rDS(ON) x D + 1 Io x VIN x tSW x FS
2
2
PLOWER = Io x rDS(ON) x (1 - D)
Use a mix of input bypass capacitors to control the voltage
overshoot across the MOSFETs. Use small ceramic
capacitors for high frequency decoupling and bulk capacitors
to supply the current needed each time Q1 turns on. Place
the small ceramic capacitors physically close to the
MOSFETs and between the drain of Q1 and the source of Q2.
The important parameters for the bulk input capacitor are the
voltage rating and the RMS current rating. For reliable
operation, select the bulk capacitor with voltage and current
ratings above the maximum input voltage and largest RMS
current required by the circuit. The capacitor voltage rating
should be at least 1.25 times greater than the maximum
input voltage and a voltage rating of 1.5 times is a
conservative guideline. The RMS current rating requirement
for the input capacitor of a buck regulator is approximately
1/2 the DC load current.
For a through hole design, several electrolytic capacitors
(Panasonic HFQ series or Nichicon PL series or Sanyo
MV-GX or equivalent) may be needed. For surface mount
designs, solid tantalum capacitors can be used, but caution
must be exercised with regard to the capacitor surge current
rating. These capacitors must be capable of handling the
surge-current at power-up. The TPS series available from
AVX, and the 593D series from Sprague are both surge
current tested.
MOSFET Selection/Considerations
Where: D is the duty cycle = VOUT / VIN ,
tSW is the switch ON time, and
FS is the switching frequency.
Standard-gate MOSFETs are normally recommended for
use with the HIP6004A. However, logic-level gate MOSFETs
can be used under special circumstances. The input voltage,
upper gate drive level, and the MOSFET’s absolute gate-tosource voltage rating determine whether logic-level
MOSFETs are appropriate.
Figure 9 shows the upper gate drive (BOOT pin) supplied by
a bootstrap circuit from VCC. The boot capacitor, CBOOT
develops a floating supply voltage referenced to the PHASE
pin. This supply is refreshed each cycle to a voltage of VCC
less the boot diode drop (VD) when the lower MOSFET, Q2
turns on. Logic-level MOSFETs can only be used if the
MOSFET’s absolute gate-to-source voltage rating exceeds
the maximum voltage applied to VCC.
+12V
DBOOT
VCC
HIP6004A
In high-current applications, the MOSFET power dissipation,
package selection and heatsink are the dominant design
factors. The power dissipation includes two loss
components; conduction loss and switching loss. The
conduction losses are the largest component of power
dissipation for both the upper and the lower MOSFETs.
These losses are distributed between the two MOSFETs
according to duty factor (see the equations below). Only the
upper MOSFET has switching losses, since the Schottky
rectifier clamps the switching node before the synchronous
rectifier turns on. These equations assume linear voltagecurrent transitions and do not adequately model power loss
due the reverse-recovery of the lower MOSFET’s body
diode. The gate-charge losses are dissipated by the
HIP6004A and don't heat the MOSFETs. However, large
gate-charge increases the switching interval, tSW which
increases the upper MOSFET switching losses. Ensure that
both MOSFETs are within their maximum junction
temperature at high ambient temperature by calculating the
10
BOOT
CBOOT
UGATE
The HIP6004A requires 2 N-Channel power MOSFETs.
These should be selected based upon rDS(ON) , gate supply
requirements, and thermal management requirements.
+5V OR +12V
+ VD -
Q1
PHASE
-
+
LGATE
PGND
NOTE:
VG-S ≈ VCC -VD
Q2
D2
NOTE:
VG-S ≈ VCC
GND
FIGURE 9. UPPER GATE DRIVE - BOOTSTRAP OPTION
Figure 10 shows the upper gate drive supplied by a direct
connection to VCC . This option should only be used in
converter systems where the main input voltage is +5VDC
or less. The peak upper gate-to-source voltage is
approximately VCC less the input supply. For +5V main
power and +12VDC for the bias, the gate-to-source voltage
of Q1 is 7V. A logic-level MOSFET is a good choice for Q1
and a logic-level MOSFET can be used for Q2 if its
absolute gate-to-source voltage rating exceeds the
maximum voltage applied to VCC .
HIP6004A
+12V
+5V OR LESS
VCC
HIP6004A
BOOT
UGATE
Q1
PHASE
-
+
LGATE
PGND
NOTE:
VG-S ≈ VCC -5V
Q2
D2
NOTE:
VG-S ≈ VCC
GND
FIGURE 10. UPPER GATE DRIVE - DIRECT VCC DRIVE OPTION
Schottky Selection
Rectifier D2 is a clamp that catches the negative inductor
swing during the dead time between turning off the lower
MOSFET and turning on the upper MOSFET. The diode
must be a Schottky type to prevent the lossy parasitic
MOSFET body diode from conducting.
11
It is acceptable to omit the diode and let the body diode of
the lower MOSFET clamp the negative inductor swing, but
efficiency will drop one or two percent as a result. The
diode's rated reverse breakdown voltage must be greater
than the maximum input voltage
HIP6004A
HIP6004A DC-DC Converter Application Circuit
Application Note AN9672. Although the Application Note
details the HIP6004, the same evaluation platform can be
used to evaluate the HIP6004A.
Figure 11 shows an application circuit of a DC-DC Converter
for an Intel Pentium Pro Microprocessor. Detailed
information on the circuit, including a complete Bill-ofMaterials and circuit board description, can be found in
VIN =
F1
+5V
OR
+12V
L1 - 1µH
C1
5x 1000µF
2x 1µF
2N6394
+12V
2K
D1
0.1µF
1000pF
VCC
OVP
18
19
2 OCSET
MONITOR
AND
PROTECTION
SS 3
12 PGOOD
15 BOOT
VSEN 1
0.1µF
RT
VID0
VID1
VID2
VID3
VID4
FB
20
4
5
6
7
8
1K
OSC
14 UGATE
13 PHASE
HIP6004A
-
17 LGATE
+
+
-
16 PGND
9
11
COMP
2.2nF
GND
20K
8.2nF
0.1µF
15
Component Selection Notes
C0
C1
9 Each 1000µF 6.3W VDC, Sanyo MV-GX or Equivalent
L1
-
D1
- 1N4148 or Equivalent
D2
- 3A, 40V Schottky, Motorola MBR340 or Equivalent
L2
5 Each 330µF 25W VDC, Sanyo MV-GX or Equivalent
Core: Micrometals T50-52B; Each Winding: 10 Turns of 16AWG
Core: Micrometals T50-52; Winding: 5 Turns of 18AWG
Q1 , Q2- Intersil MOSFET; RFP70N03
FIGURE 11. PENTIUM PRO DC-DC CONVERTER
12
L2
3µH
D/A
10
1.33K
0.1µF
Q1
Q2
D2
CO
9x 1000µF
+VO
HIP6004A
Small Outline Plastic Packages (SOIC)
M20.3 (JEDEC MS-013-AC ISSUE C)
N
20 LEAD WIDE BODY SMALL OUTLINE PLASTIC PACKAGE
INDEX
AREA
0.25(0.010) M
H
B M
INCHES
E
-B1
2
3
L
SEATING PLANE
-A-
h x 45o
A
D
-C-
e
A1
B
C
0.10(0.004)
0.25(0.010) M
C A M
SYMBOL
MIN
MAX
MIN
MAX
NOTES
A
0.0926
0.1043
2.35
2.65
-
A1
0.0040
0.0118
0.10
0.30
-
B
0.013
0.0200
0.33
0.51
9
C
0.0091
0.0125
0.23
0.32
-
D
0.4961
0.5118
12.60
13.00
3
E
0.2914
0.2992
7.40
7.60
4
e
µα
B S
0.050 BSC
1.27 BSC
-
H
0.394
0.419
10.00
10.65
-
h
0.010
0.029
0.25
0.75
5
L
0.016
0.050
0.40
1.27
6
N
α
NOTES:
MILLIMETERS
20
0o
20
8o
0o
7
8o
1. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of
Publication Number 95.
Rev. 0 12/93
2. Dimensioning and tolerancing per ANSI Y14.5M-1982.
3. Dimension “D” does not include mold flash, protrusions or gate burrs.
Mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006
inch) per side.
4. Dimension “E” does not include interlead flash or protrusions. Interlead
flash and protrusions shall not exceed 0.25mm (0.010 inch) per side.
5. The chamfer on the body is optional. If it is not present, a visual index
feature must be located within the crosshatched area.
6. “L” is the length of terminal for soldering to a substrate.
7. “N” is the number of terminal positions.
8. Terminal numbers are shown for reference only.
9. The lead width “B”, as measured 0.36mm (0.014 inch) or greater
above the seating plane, shall not exceed a maximum value of
0.61mm (0.024 inch)
10. Controlling dimension: MILLIMETER. Converted inch dimensions
are not necessarily exact.
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.
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13