2-152

HIP6012

Buck and Synchronous-Rectifier
Pulse-Width Modulator (PWM) Controller

The HIP6012 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 HIP6012 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 HIP60012 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/

s slew rate which enables high converter bandwidth for

fast transient performance. The resulting PWM duty ratio
ranges from 0% to 100%.

The HIP6012 protects against over-current conditions by
inhibiting PWM operation. The HIP6012 monitors the current
by using the r

DS(ON)

of the upper MOSFET which eliminates

the need for a current sensing resistor.

Pinout

HIP6012

(SOIC)

TOP VIEW

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

- 1.27V Internal Reference

1.5% Over Line Voltage and Temperature

· Over-Current Fault Monitor

- Does Not Require Extra Current Sensing Element

- Uses MOSFETs r

DS(ON)

· Small Converter Size

- Constant Frequency Operation

- 200kHz Free-Running Oscillator Programmable from

50kHz to Over 1MHz

· 14 Pin, SOIC Package

Applications

· Power Supply for Pentium®, Pentium Pro, PowerPCTM and

AlphaTM Microprocessors

· High-Power 5V to 3.xV DC-DC Regulators

· Low-Voltage Distributed Power Supplies

PowerPCTM is a trademark of IBM.

AlphaTM is a trademark of Digital Equipment Corporation.

Pentium® is a registered trademark of Intel Corporation.

OCSET

COMP

VCC

LGATE

PGND

BOOT

UGATE

PHASE

GND

PVCC

Ordering Information

PART NUMBER

TEMP.

RANGE (

PACKAGE

PKG.

NO.

HIP6012CB

0 to 70

14 Ld SOIC

M14.15

Data Sheet

June 1997

File Number

4324

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.

http://www.intersil.com or 407-727-9207

Intersil Corporation 1999

2-154

Absolute Maximum Ratings

Thermal Information

Supply Voltage, V

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +15.0V

Boot Voltage, V

BOOT

- V

PHASE

. . . . . . . . . . . . . . . . . . . . . . . +15.0V

Input, Output or I/O Voltage . . . . . . . . . . . . GND -0.3V to V

+0.3V

ESD Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Class 2

Operating Conditions

Supply Voltage, V

. . . . . . . . . . . . . . . . . . . . . . . . . . . +12V

10%

Ambient Temperature Range . . . . . . . . . . . . . . . . . . . . . 0

C to 70

Junction Temperature Range . . . . . . . . . . . . . . . . . . . . 0

C to 125

Thermal Resistance (Typical, Note 1)

(

C/W)

SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

115

Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . 150

Maximum Storage Temperature Range . . . . . . . . . . -65

C to 150

Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300

(Lead tips only)

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:

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

EN = V

; UGATE and LGATE Open

Shutdown Supply

EN = 0V

100

POWER-ON RESET

Rising V

Threshold

OCSET

= 4.5VDC

10.4

Falling V

Threshold

OCSET

= 4.5VDC

8.8

Enable - Input threshold Voltage

OCSET

= 4.5VDC

0.8

2.0

Rising V

OCSET

Threshold

1.27

OSCILLATOR

Free Running Frequency

= OPEN, V

= 12

180

200

220

kHz

Total Variation

< R

to GND < 200k

-20

+20

Ramp Amplitude

OSC

= OPEN

1.9

P-P

REFERENCE

Reference Voltage

1.251

1.270

1.289

ERROR AMPLIFIER

DC Gain

Gain-Bandwidth Product

GBW

MHz

Slew Rate

COMP = 10pF

GATE DRIVERS

Upper Gate Source

UGATE

BOOT

- V

PHASE

= 12V, V

UGATE

= 6V

350

500

Upper Gate Sink

UGATE

LGATE

= 0.3A

5.5

Lower Gate Source

LGATE

= 12V, V

LGATE

= 6V

300

450

Lower Gate Sink

LGATE

= 0.3A

3.5

6.5

PROTECTION

OCSET Current Source

OCSET

= 4.5VDC

170

200

230

Soft Start Current

HIP6012

2-155

Functional Pin Description

RT (Pin 1)

This pin provides oscillator switching frequency adjustment.
By placing a resistor (R

) from this pin to GND, the nominal

200kHz switching frequency is increased according to the
following equation:

Conversely, connecting a pull-up resistor (R

) from this pin

to V

reduces the switching frequency according to the

following equation.:

OCSET (Pin 2)

Connect a resistor (R

OCSET

) from this pin to the drain of the

upper MOSFET. R

OCSET

, an internal 200

A current source

OCS

), and the upper MOSFET on-resistance (r

DS(ON)

) set

the converter over-current (OC) trip point according to the
following equation:

An over-current trip cycles the soft-start function.

SS (Pin 3)

Connect a capacitor from this pin to ground. This capacitor,
along with an internal 10

A current source, sets the soft-

start 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 levels are 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.

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.

Typical Performance Curves

FIGURE 1. R

RESISTANCE vs FREQUENCY

FIGURE 2. BIAS SUPPLY CURRENT vs FREQUENCY

100

1000

SWITCHING FREQUENCY (kHz)

RESIST

ANCE (k

)

100

1000

PULLUP

TO +12V

PULLDOWN

TO V

100

200

300

400

500

600

700

800

900

1000

VCC

(mA)

SWITCHING FREQUENCY (kHz)

GATE

= 1000pF

GATE

= 3300pF

GATE

= 10pF

OCSET

COMP

VCC

LGATE

PGND

BOOT

UGATE

PHASE

GND

PVCC

200kHz

------------------

to GND)

200kHz

------------------

to 12V)

PEAK

OCS

OCSET

DS ON

(

)

--------------------------------------------

HIP6012

2-156

PGND (Pin 11)

This is the power ground connection. Tie the lower MOSFET
source to this pin.

LGATE (Pin 12)

Connect LGATE to the lower MOSFET gate. This pin
provides the gate drive for the lower MOSFET.

PVCC (Pin 13)

Provide a bias supply for the lower gate drive to this pin.

VCC (Pin 14)

Provide a 12V bias supply for the chip to this pin.

Functional Description

Initialization

The HIP6012 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

) on the OCSET pin. The level on OCSET is

equal to V

Less a fixed voltage drop (see over-current

protection). With the EN pin held to V

, 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

and V

are equivalent and the

+12V power source must exceed the rising V

threshold

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
10

A current source charges an external capacitor (C

) 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
C

= 0.1

F. 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 reference
voltage and the output voltage is in regulation. This method
provides a rapid and controlled output voltage rise.

Over-Current Protection

The over-current function protects the converter from a
shorted output by using the upper MOSFETs on-resistance,
r

DS(ON)

to monitor the current. This method enhances the

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

OCSET

)

programs the over-current trip level. An internal 200

(typical) current sink develops a voltage across R

OCSET

that

is reference to V

. When the voltage across the upper

MOSFET (also referenced to V

) exceeds the voltage

across R

OCSET

, the over-current function initiates a soft-

start sequence. The soft-start function discharges C

with

a 10

A current sink and inhibits PWM operation. The soft-

start function recharges C

, and PWM operation resumes

with the error amplifier clamped to the SS voltage. Should an
overload occur while recharging C

, the soft start function

inhibits PWM operation while fully charging C

to 4V to

complete its cycle. Figure 4 shows this operation with an

TIME (5ms/DIV)

SOFT-START
(1V/DIV)

OUTPUT

(1V/DIV)

VOLTAGE

FIGURE 3. SOFT-START INTERVAL

OUTPUT INDUCT

SOFT

-ST

TIME (20ms/DIV)

10A

15A

FIGURE 4. OVER-CURRENT OPERATION

HIP6012

Part Number HIP6012