Datasheet HIP6013 Datasheet (intersil)

Page 1
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HIP6013
Data Sheet June 1997
Buck Pulse-Width Modulator (PWM) Controller
The HIP6013 provides complete control and protection for a DC-DC converter optimized for high-performance microprocessor applications. It is designed to drive an N-Channel MOSFET in a standard buck topology. The HIP6013 integrates all of the control, output adjustment, monitoring and protection functions into a single package.
The output voltage of the converter can be precisely regulated to as low as 1.27V, with a maximum tolerance of ±1.5% over temperature and line voltage variations.
The HIP6013 provides simple,single feedback loop, voltage­mode 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/µs slew rate which enables high converter bandwidth for fast transient performance. The resulting PWM duty ratio ranges from 0% to 100%.
The HIP6013 protects against over-current conditions by inhibiting PWM operation. The HIP6013 monitors the current by using the r
DS(ON)
the need for a current sensing resistor.
of the upper MOSFET which eliminates
File Number
Features
• Drives N-Channel MOSFET
• 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
- 1.27V Internal Reference
- ±1.5% Over Line Voltage and Temperature
• Over-Current Fault Monitor
- Does Not Require Extra Current Sensing Element
- Uses MOSFET’s r
DS(on)
• Small Converter Size
- Constant Frequency Operation
- 200kHz Free-Running Oscillator Programmable from 50kHz to Over 1MHz
• 14 Pin, SOIC Package
Applications
4325
Ordering Information
TEMP.RANGE
PART NUMBER
HIP6013CB 0 to 70 14 Ld SOIC M14.15
(oC) PACKAGE
PKG.
NO.
Pinout
HIP6013
(SOIC)
TOP VIEW
RT
OCSET
SS
COMP
FB EN
GND
1 2 3 4 5 6 7
14 13 12 11 10 9 8
VCC NC NC NC BOOT UGATE PHASE
• Power Supply for Pentium®, Pentium Pro, PowerPC™and Alpha™ Microprocessors
• High-Power 5V to 3.xV DC-DC Regulators
• Low-Voltage Distributed Power Supplies
PowerPC™ is a trademark of IBM.
Alpha™ is a trademark of Digital Equipment Corporation.
Pentium® is a registered trademark of Intel Corporation.
2-162
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
http://www.intersil.com or 407-727-9207
| Copyright © Intersil Corporation 1999
Page 2
Typical Application
12V
VCC
HIP6013
+5V OR +12V
Block Diagram
SS
RT
FB
REF
MONITOR AND
PROTECTION
OSC
HIP6013
+
-
COMP
OCSET EN
BOOT
UGATE
+V
PHASE
­+
VCC
POWER-ON
RESET (POR)
O
EN
OCSET
FB
COMP
RT
REFERENCE
200µA
1.27 VREF +
-
ERROR
AMP
+
-
OVER-
CURRENT
4V
PWM
COMPARATOR
OSCILLATOR
10µA
SOFT-
START
+
-
INHIBIT
PWM
GATE
CONTROL
LOGIC
SS BOOT
UGATE PHASE
GND
2-163
Page 3
HIP6013
Absolute Maximum Ratings Thermal Information
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +15.0V
Boot Voltage, V
BOOT
- V
. . . . . . . . . . . . . . . . . . . . . . . +15.0V
PHASE
Input, Output or I/O Voltage. . . . . . . . . . . GND -0.3V to VCC +0.3V
ESD Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Class 2
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 operationofthe 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 an evaluation PC board in free air.
Electrical Specifications Recommended Operating Conditions, Unless Otherwise Noted
PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNITS
VCC SUPPLY CURRENT
Nominal Supply I
CC
Shutdown Supply EN = 0V - 50 100 µA
POWER-ON RESET
Rising VCC Threshold V Falling VCC Threshold V Enable - Input threshold Voltage V Rising V
Threshold - 1.27 - V
OCSET
OSCILLATOR
Free Running Frequency RT = OPEN, VCC= 12 180 200 220 kHz Total Variation 6kΩ < RT to GND < 200kΩ -20 - +20 % Ramp Amplitude ∆V
OSC
REFERENCE
Reference Voltage 1.251 1.270 1.289 V
ERROR AMPLIFIER
DC Gain -88- dB Gain-Bandwidth Product GBW - 15 - MHz Slew Rate SR COMP = 10pF - 6 - V/µs
GATE DRIVERS
Upper Gate Source I Upper Gate Sink R
UGATE
UGATEILGATE
PROTECTION
OCSET Current Source I Soft Start Current I
OCSETVOCSET
SS
EN = VCC; UGATE and LGATE Open - 5 - mA
= 4.5VDC - - 10.4 V
OCSET
= 4.5VDC 8.8 - - V
OCSET
= 4.5VDC 0.8 - 2.0 V
OCSET
RT = OPEN - 1.9 - V
V
- V
BOOT
PHASE
= 0.3A - 5.5 10 Ω
= 4.5VDC 170 200 230 µA
Thermal Resistance (Typical, Note 1) θJA (oC/W)
SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . 150oC
Maximum Storage Temperature Range. . . . . . . . . . -65oC to 150oC
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300oC
(SOIC - Lead Tips Only)
= 12V, V
= 6V 350 500 - mA
UGATE
-10- µA
P-P
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Page 4
Typical Performance Curves
HIP6013
40
RT PULLUP
1000
100
RESISTANCE (kΩ)
10
10 100 1000
SWITCHING FREQUENCY (kHz)
FIGURE 1. RT RESISTANCE vs FREQUENCY FIGURE 2. BIAS SUPPLY CURRENT vs FREQUENCY
TO +12V
RT PULLDOWN
TO V
SS
Functional Pin Description
1
RT
OCSET
SS
COMP
FB EN
GND
2 3 4 5 6 7
RT (Pin 1)
This pin provides oscillator switching frequency adjustment. By placing a resistor (R 200kHz switching frequency is increased according to the following equation:
510
Fs 200kHz
•
------------------+≈
R
Conversely, connecting a pull-up resistor (R to VCC reduces the switching frequency according to the following equation.:
410
Fs 200kHz
•
------------------–≈
R
) from this pin to GND, the nominal
T
6
T
T
(RT to GND)
7
(RT to 12V)
14 13 12 11 10
9 8
VCC NC NC NC BOOT UGATE PHASE
) from this pin
T
35
30
25
20
(mA)
CC
I
15
10
5
0
100 200 300 400 500 600 700 800 900 1000
C
= 3300pF
GATE
C
= 1000pF
GATE
C
= 10pF
GATE
SWITCHING FREQUENCY (kHz)
SS (Pin 3)
Connect a capacitor from this pin to ground. This capacitor, along with an internal 10µA current source, sets the soft­start interval of the converter.
COMP (Pin 4) and FB (Pin 5)
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.
EN (Pin 6)
This pin is the open-collector enable pin. Pull this pin below 1V to disable the converter. In shutdown, the soft start pin is discharged and the UGATE and LGATE pins are held low.
GND (Pin 7)
Signal ground for the IC.All voltage levelsare measured with respect to this pin.
PHASE (Pin 8)
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.
OCSET (Pin 2)
Connect a resistor (R upper MOSFET. R (I
), and the upper MOSFET on-resistance (r
OCS
OCSET
the converter over-current (OC) trip point according to the following equation:
I
•
I
PEAK
OCSROCSET
------------------------------------------- -=
r
DS ON()
An over-current trip cycles the soft-start function.
) from this pin to the drain of the
OCSET
, an internal 200µA current source
DS(ON)
2-165
) set
UGATE (Pin 9)
Connect UGATE to the upper MOSFET gate. This pin provides the gate drive for the upper MOSFET.
BOOT (Pin 10)
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.
VCC (Pin 14)
Provide a 12V bias supply for the chip to this pin.
Page 5
Functional Description
Initialization
The HIP6013 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 and the enable (EN) pin. The POR monitors the bias voltage at the VCC pin and the input voltage (V equal to V protection). With the EN pin held to VCC, the POR function initiates soft start operation after both input supply voltages exceed their POR thresholds. For operation with a single +12V power source, V +12V power source must exceed the rising V before POR initiates operation.
The Power-On Reset (POR) function inhibits operation with the chip disabled (EN pin low). With both input supplies above their POR thresholds, transitioning the EN pin high initiates a soft start interval.
Soft Start
The POR function initiates the soft start sequence. An internal 10µA current source charges an external capacitor (C
SS
amplifier output (COMP pin) and reference input (+ terminal of error amp) to the SS pin voltage. Figure 3 shows the soft start interval with C 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 reference voltage and the output voltage is in regulation. This method provides a rapid and controlled output voltage rise.
) on the OCSET pin. The level on OCSET is
IN
less a fixed voltage drop (see over-current
IN
and VCC are equivalent and the
IN
threshold
CC
) on the SS pin to 4V. Soft start clamps the error
= 0.1µF. Initially the clamp on the
SS
HIP6013
SOFT-START (1V/DIV)
OUTPUT VOLTAGE
0V
0V
t1 t2 t3
TIME (5ms/DIV)
FIGURE 3. SOFT-START INTERVAL
(1V/DIV)
Over-Current Protection
The over-current function protects the converter from a shorted output by using the upper MOSFET’s on-resistance, r converter’s efficiency and reduces cost by eliminating a current sensing resistor.
The over-current function cycles the soft-start function in a hiccup mode to provide fault protection. A resistor (R programs the over-current trip level. An internal 200µA (typical) current sink develops a voltage across R is reference to V MOSFET (also referenced to V across R start sequence. The soft-start function discharges C a 10µA current sink and inhibits PWM operation. The soft­start function recharges C with the error amplifier clamped to the SS voltage. Should an overload occur while recharging C inhibits PWM operation while fully charging C complete its cycle. Figure 4 shows this operation with an overload condition. Note that the inductor current increases to over 15A during the C 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.
to monitor the current. This method enhances the
DS(ON)
. When the voltage across the upper
IN
, the over-current function initiates a soft-
OCSET
SS
) exceeds the voltage
IN
, and PWM operation resumes
SS
, the soft start function
SS
charging interval and causes an
OCSET
to 4V to
SS
OCSET
that
with
SS
)
2-166
Page 6
4V
HIP6013
V
IN
2V
SOFT-START
0V
15A
10A
5A
OUTPUT INDUCTOR
0A
TIME (20ms/DIV)
FIGURE 4. OVER-CURRENT OPERATION
The over-current function will trip at a peak inductor current (I
) determined by:
PEAK
I
PEAK
where I
I
---------------------------------------------------=
OCSET
•
OCSETROCSET
r
DS ON()
is the internal OCSET current source (200µA
- typical). The OC trip point varies mainly due to the MOSFET’sr
DS(ON)
in the normal operating load range, find the R
variations. To avoid over-current tripping
OCSET
resistor
from the equation above with:
1. Themaximumr
2. The minimum I
3. Determine ,
I
PEAK
DS(ON) OCSET
atthehighest junction temperature.
from the specification table.
for I
PEAKIOUT MAX()
∆I()2⁄+>
where ∆I is the output inductor ripple current.
For an equation for the ripple current see the section under component guidelines titled ‘Output Inductor Selection’.
A small ceramic capacitor should be placed in parallel with R
to smooth the voltage across R
OCSET
OCSET
in the
presence of switching noise on the input voltage.
Application Guidelines
Layout Considerations
As in any high frequency switching conv erter , la y out is very important. Switching current from one power device to 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.
HIP6013
UGATE
PHASE
FIGURE 5. PRINTED CIRCUIT BOARD
POWER AND GROUND PLANES OR ISLANDS
Q1
D2
RETURN
L
O
V
OUT
C
IN
C
O
LOAD
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 components shown in Figure 6 should be located as close together as possible. Please note that the capacitors C
IN
and CO each represent numerous physical capacitors. Locate the HIP6013 within 3 inches of the MOSFETs, Q1. The circuit traces for the MOSFETs’ gate and source connections from the HIP6013 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, C
ss
close to the SS pin because the internal current source is only 10µA. Provide local V GND pins. Locate the capacitor,C
decoupling between VCC and
CC
as close as practical
BOOT
to the BOOT and PHASE pins.
+V
IN
BOOT C
BOOT
HIP6013
SS
C
SS
GND
FIGURE 6. PRINTED CIRCUIT BOARD
SMALL SIGNAL LAYOUT GUIDELINES
PHASE V
CC
+12V
D1
C
VCC
Q1
D2
L
O
C
V
OUT
O
LOAD
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Page 7
HIP6013
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 (V 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).
OSC
PWM
COMPARATOR
-
∆V
OSC
+
Z
FB
V
E/A
-
+
ERROR AMP
REFERENCE
DETAILED COMPENSATION COMPONENTS
C2
C1
COMP
HIP6013
FIGURE 7. VOLTAGE - MODE BUCK CONVERTER
COMPENSATION DESIGN
The modulator transfer function is the small-signal transfer function of Vout/V
. This function is dominated by a DC
E/A
Gain and the output filter (Lo and Co), with a double pole break frequency at F
and a zero at F
LC
the modulator is simply the input voltage (Vin) divided by the peak-to-peak oscillator voltage ∆V
) is compared with the
E/A
V
DRIVER
DRIVER
Z
R2
-
+
REF
IN
PHASE
IN
Z
FB
FB
ESR
.
OSC
L
O
C
O
ESR
(PARASITIC)
V
OUT
Z
IN
C3
R3
R1
. The DC Gain of
V
OUT
Modulator Break Frequency Equations
F
LC =
2π LOCO••
F
ESR
=
1
-------------------------------------- -
The compensation network consists of the error amplifier (internal to the HIP6013) and the impedance networks Z and ZFB. The goal of the compensation network is to provide a closed loop transfer function with the highest 0dB crossing frequency (f
) and adequate phase margin. Phase margin
0dB
is the difference between the closed loop phase at f
o
180
. The equations below relate the compensation network’s poles, zeros and gain to the components (R1, R2, R3, C1, C2, and C3) in Figure 8. Use these guidelines for locating the poles and zeros of the compensation network:
1
--------------------------------------------
2π ESR C
•()•
0dB
O
IN
and
Compensation Break Frequency Equations
1
---------------------------------
F
=
Z1
2π R2 C1••
-----------------------------------------------------
FZ2=
2π R1 + R3()• C3•
1
----------------------------------------------------- -
FP1=
2π R2•
---------------------------------
FP2=
2π R3• C3•
1. Pick Gain (R2/R1) for desired converter bandwidth
ST
2. Place 1 (~75% F
3. Place 2
4. Place 1
5. Place 2
Zero Below Filter’s Double Pole
)
LC
ND
Zero at Filter’s Double Pole
ST
Pole at the ESR Zero
ND
Pole at Half the Switching Frequency
6. Check Gain against Error Amplifier’s Open-Loop Gain
7. Estimate Phase Margin - Repeat if Necessary
Figure 8 shows an asymptotic plot of the DC-DC converter’s gain vs frequency. The actual Modulator Gain has a high gain peak do 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 the compensation gain. Check the compensation gain at F 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 Z
and ZINto provide a stable,high bandwidth (BW) overall
FB
loop. A stable control loop has a gain crossing with
-20dB/decade slope and a phase margin greater than 45 Include worst case component variations when determining phase margin.
1
C1 C2•

--------------------- -
•

C1 + C2
1
with the
P2
o
.
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Page 8
HIP6013
100
80
60
40
20LOG (R2/R1)
20
GAIN (dB)
0
MODULATOR
-20
-40
-60
FIGURE 8. ASYMPTOTIC BODE PLOT OF CONVERTER GAIN
GAIN
F
F
F
P1
Z2
Z1
F
LC
F
FREQUENCY (Hz)
(V
ESR
F
P2
20LOG
/∆V
IN
OSC
OPEN LOOP ERROR AMP GAIN
)
COMPENSATION GAIN
CLOSED LOOP GAIN
10M1M100K10K1K10010
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 Pentium-Pro be composed of at least forty (40) 1.0µF 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=
V
IN-VOUT
------------------------------- -
Fs LO×
V
--------------- -
•
OUT
V
IN
∆ V
OUT
= ∆I x ESR
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 HIP6013 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 b y 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:
x I
L
O
t
=
RISE
where: I
TRAN
VIN - V
O
is the transient load current step, t
TRAN
t
FALL
response time to the application of load, and t
x I
L
O
V
TRAN
O
RISE
FALL
is the
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 output voltage setting. Be sure to check both of these equations at the minimum and maximum output levelsforthe worst case response time.
Input Capacitor Selection
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 anode of Schottky diode D2.
The important parameters for the bulk input capacitor are the voltage rating and the RMS current rating. For reliable
2-169
Page 9
HIP6013
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 MV­GX 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
The HIP6013 requires an N-Channel power MOSFET. It should be selected based upon r requirements, and thermal management requirements.
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 the MOSFET. Switching losses also contribute to the overall MOSFET power loss (see the equations below). These equations assume linear voltage­current transitions and are approximations. The gate­charge losses are dissipated by the HIP6013 and don't heat the MOSFET. However, large gate-charge increases the switching interval, t
, which increases the upper
SW
MOSFET switching losses. Ensure that the MOSFET is within its maximum junction temperature at high ambient temperature by calculating the 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.
P
COND
P
SW
=
2
= I
x r
O
DS(ON)
1
IO x VIN x tSW x Fs
2
x D
DS(ON)
, gate supply
Standard-gate MOSFETs are normally recommended for use with the HIP6013. 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 V
. The boot capacitor, C
CC
BOOT
develops a floating supply voltage referenced to the PHASE pin. This supply is refreshed each cycle to a voltage of V
CC
less the boot diode drop (VD) when the lower MOSFET, Q2 turns on. A logic-level MOSFET can only be used for Q1 if the MOSFET’s absolute gate-to-source voltage rating exceeds the maximum voltage applied to V
CC
.
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 V
less the input supply. For +5V main
CC
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 is a good choice for Q1 under these conditions.
+12V
HIP6013
-
+
FIGURE 9. UPPER GATE DRIVE - BOOTSTRAP OPTION
VCC
D
BOOT
BOOT
UGATE PHASE
GND
C
BOOT
+5V OR +12V
Q1
D2
NOTE: V
G-S
≈ V
CC
- V
D
Where: D is the duty cycle = V
is the switching interval, and
t
SW
Fs is the switching frequency.
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/ VIN,
O
Page 10
HIP6013
+12V
VCC
HIP6013
­+
FIGURE 10. UPPER GATE DRIVE - DIRECT VCC DRIVE OPTION
BOOT
UGATE PHASE
GND
+5V OR LESS
Q1
D2
NOTE:
V
G-S
≈ V
CC
- 5V
Schottky Selection
Rectifier D2 conducts when the upper MOSFET Q1 is off. The diode should be a Schottky type for low power losses. The power dissipation in the Schottky rectifier is approximated by:
P
Where: D is the duty cycle = VO/VIN, and
In addition to power dissipation, package selection and heatsink requirements are the main design tradeoffs in choosing the Schottky rectifier. Since the three f actors are interrelated, the selection process is an iterative procedure. The maximum junction temperature of the rectifier must remain below the manufacturer’s specified value, typically 125 and the Schottky power dissipation equation (shown abov e), the junction temperature of the rectifier can be estimated. Be sure to use the available airflo w and ambient temper ature to determine the junction temperature rise.
= IO x Vf x (1 - D)
COND
is the schottky forward voltage drop
V
f
o
C.By using the package thermal resistance specification
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Page 11
HIP6013
HIP6013 DC-DC Converter Application Circuit
The figure below shows a DC-DC converter circuit for a microprocessor application, originally designed to employ the HIP6007 controller. Giv en the similarities between the HIP6007 and HIP6013 controllers, the circuit can be implemented using the HIP6013 controller without any modifications.Howev er, given the expanded reference voltage
12VCC
VIN
C1-5
3x 680µF
RTN
tolerance range, the HIP6013-based conv erter may require additional output capacitance. Detailed information on the circuit, including a complete Bill-of-Materials and circuit board description, can be found in application note AN9722. See Intersil’s home page on the web:http://www.intersil.com or Intersil AnswerFAX (407-724-7800) document # 99722.
C17-18 2x 1µF
1206
R7
10K
ENABLE
C13
0.1µF
R2 1K
R3 1K
R1
SPARE
Component Selection Notes:
SS RT
FB
C15
0.01µF
C16
SPARE
C12
1µF
1206
6
3
1
5
REF
C14
33pF
VCC 14
MONITOR AND
PROTECTION
OSC
U1
HIP6013
+
-
COMP
R5
15K
R4
SPARE
-
+
COMP TP1
C19
CR3
CR1
4148
C20
0.1µF
PHASE
TP2
L2
C6-11
4x 1000µF
V
OUT
RTN
1000pF
OCSET
2
10
BOOT
9
UGATE PHASE
8
NC
13
NC
12
NC
11
74
GND
R6
3.01K
Q1
JP1
C1-C3 - 3 each 680µF 25W VDC, Sanyo MV-GX or equivalent. C6-C9 - 4 each 1000µF 6.3W VDC, Sanyo MV-GX or equivalent.
L1 - Core: Micrometals T60-52; Winding: 14 Turns of 17AWG. CR1 - 1N4148 or equivalent. CR3 - 15A, 35V Schottky, Motorola MBR1535CT or equivalent.
Q1 - Intersil MOSFET; RFP25N05.
FIGURE 11. DC-DC CONVERTER APPLICATION CIRCUIT
All Intersil semiconductor products are manufactured, assembled and tested under ISO9000 quality systems certification.
Intersil semiconductor products are sold by description only .Intersil Corporation reserves the right to make changes in circuit design and/or specifications at any time with­out notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see web site http://www.intersil.com
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