Fairchild Semiconductor FAN5098 Datasheet

www.fairchildsemi.com

FAN5098

Two Phase Interleaved Synchronous Buck Converter

®

for AMD

Hammer™

Features

• Programmable output from 800mV to 1.550V in 25mV
steps using an integrated 5-bit DAC

• Two interleaved synchronous phases for maximum
performance

• 100nsec transient response time

• Built-in current sharing between phases

• Remote sense

• Programmable Active Droop



(Voltage Positioning)

• Programmable switching frequency from 100KHz to
1MHz per phase

• Adaptive delay gate switching

• Integrated high-current gate drivers

• Integrated Power Good, OV, UV, Enable/Soft Start
functions

• Drives N-channel MOSFETs

• Operation optimized for 12V operation

• High efficiency mode (E*) at light load

• Overcurrent protection using MOSFET sensing

• 24 pin TSSOP package

Applications

• VRM/VRD for 64-Bit Athlon™ and Opteron™ CPU’s

• VRM/VRD for Advanced CPU’s

• Programmable step-down power supply

Description

The FAN5098 is a synchronous two-phase DC-DC controller
IC which provides a highly accurate, programmable output
voltage for the AMD
leaved synchronous buck regulator phases with built-in cur­rent sharing operate 180° out of phase to provide the fast
transient response needed to satisfy high current applications
while minimizing external components.
The FAN5098 features Programmable Active Droop
transient response with minimum output capacitance. It has
integrated high-current gate drivers, with adaptive delay gate
switching, eliminating the need for external drive devices.
The FAN5098 uses a 5-bit D/A converter to program the out­put voltage from 800mV to 1.550V in 25mV steps with an
accuracy of 1%. The FAN5098 uses a high level of integra­tion to deliver load currents in excess of 50A from a 12V
source with minimal external circuitry.
The FAN5098 also offers integrated functions including
Power Good, Output Enable/Soft Start, under-voltage lock­out, over-voltage protection, and adjustable current limiting
with independent current sense on each phase. It is available
in a 24 pin TSSOP package.

®

Hammer™ processor. Two inter-



for

Block Diagram

23

OSC

R

T

-

+

GNDA

24

Power
Good

19

PWRGD

5-Bit
DAC

5

1234

VID2

VID1

VID3

VID4

VID0

Athlon™ and Hammer™ are registered trademarks of AMD

BYPASS

6

5V Reg

Current
Limit

DROOP/E*

®

. Programmable Active Droop is a trademark of Fairchild Semiconductor.

+12V

18

O

UVL

+

-

-

+

-

+

-

+

21

7

AGND

Digital

Control

Digital

Control

22

ENABLE/SS

+12V

+12V

20

ILIM

BOOT A

13

14

15

17

16

12

11

10

8

9

BOOT B

+12V

VO

+12V

REV. 1.0.7 2/18/03

FAN5098 PRODUCT SPECIFICATION

Pin Assignments

VID0
VID1
VID2
VID3

VID4

BYPASS

AGND

LDRVB

PGNDB

SWB

HDRVB

BOOTB

1

2
3

4
5
6
7
8
9
10
11
12

FAN5098

Pin Definitions

Pin Number Pin Name Pin Function Description

1-5 VID0-4

6 BYPASS

7 AGND

8 LDRVB

9 PGNDB

10 SWB

11 HDRVB

12 BOOTB

13 BOOTA

14 HDRVA

15 SWA

16 PGNDA

17 LDRVA

18 VCC

19 PWRGD

Voltage Identification Code Inputs. Open collector/TTL compatible inputs will

program the output voltage over the ranges specified in Table 1. Internally Pulled­Up.

5V Rail. Bypass this pin with a 0.1 µ F ceramic capacitor to AGND.

Analog Ground. Return path for low power analog circuitry. This pin should be

connected to a low impedance system ground plane to minimize ground loops.

Low Side FET Driver for B. Connect this pin to the gate of an N-channel

MOSFET for synchronous operation. The trace from this pin to the MOSFET gate
should optimally be <0.5 " .

Power Ground B. Return pin for high currents flowing in low-side MOSFET.

Connect directly to low-side MOSFET source.

High side driver source and low side driver drain switching node B. Gate

drive return for high side MOSFET, and negative input for low-side MOSFET
current sense.

High Side FET Driver B. Connect this pin to the gate of an N-channel MOSFET.

The trace from this pin to the MOSFET gate should optimally be <0.5 " .

Bootstrap B. Input supply for high-side MOSFET.

Bootstrap A. Input supply for high-side MOSFET.

High Side FET Driver A. Connect this pin to the gate of an N-channel MOSFET.

The trace from this pin to the MOSFET gate should optimally be <0.5 " .

High side driver source and low side driver drain switching node A. Gate

drive return for high side MOSFET, and negative input for low-side MOSFET
current sense.

Power Ground A. Return pin for high currents flowing in low-side MOSFET.

Connect directly to low-side MOSFET source.

Low Side FET Driver for A. Connect this pin to the gate of an N-channel

MOSFET for synchronous operation. The trace from this pin to the MOSFET gate
should optimally be <0.5 " .

VCC. Internal IC supply. Connect to system 12V supply, and decouple with a 10 Ω

resistor and 1 µ F ceramic capacitor.

Power Good Flag. An open collector output that will be logic LOW if the output

voltage is less than 350mV less than the nominal output voltage setpoint. Power
Good is prevented from going low until the output voltage is out of spec for
500µsec.

24
23
22

21
20
19
18

17
16
15
14
13

VFB
RT
ENABLE/SS

DROOP/E*
ILIM
PWRGD
VCC
LDRVA
PGNDA
SWA
HDRVA
BOOTA

2

REV. 1.0.7 2/18/03

°

° C

°

16 °

84 °

°

PRODUCT SPECIFICATION FAN5098

Pin Number Pin Name Pin Function Description

20 ILIM

21 DROOP/E*

Current Limit. A resistor from this pin to ground sets the over current trip level.

Droop Control/Energy Star Mode Control. A resistor from this pin to ground

sets the amount of droop by controlling the gain of the current sense amplifier.
When this pin is pulled high to BYPASS, the phase A drivers are turned off for
Energy-star operation.

22 ENABLE/SS Output Enable/Softstart. A logic LOW on this pin will disable the output. An

10µA internal current source allows for open collector control. This pin also
doubles as soft start.

23 RT

24 VFB

Frequency Set. A resistor from this pin to ground sets the switching frequency.

Voltage Feedback. Connect to the desired regulation point at the output of the

converter.

Absolute Maximum Ratings

(Absolute Maximum Ratings are the values beyond which the device

may be damaged or have it’s useful life impaired. Functional operation under these conditions is not implied.)

Parameter Min. Max. Unit

Supply Voltage VCC 15 V

Supply Voltages BOOT to PGND 24 V

BOOT to SW 24 V

Voltage Identification Code Inputs, VID0-VID4 6 V

VFB, ENABLE/SS, PWRGD, DROOP/E* 6 V

SWA, SWB to AGND (<1µs) -3 15 V

PGNDA, PGNDB to AGND -0.5 0.5 V

Gate Drive Current, peak pulse 3 A

Junction Temperature, T

J

-55 150

C

Storage Temperature -65 150

Thermal Ratings

Parameter Min. Typ. Max. Unit

Lead Soldering Temperature, 10 seconds 300

Power Dissipation, P

Thermal Resistance Junction-to-Case, Θ

D

JC

Thremal Resistance Junction-to-Ambient, Θ

JA

650 mW

C

C/W

C/W

Recommended Operating Conditions (See Figure 2)

Parameter Conditions Min. Max. Units

Output Driver Supply, BOOTA, B 16 22 V

Ambient Operating Temperature 0 70

Supply Voltage V

REV. 1.0.7 2/18/03

CC

10.8 13.2 V

C

3

•

•

•

∆

•

FAN5098 PRODUCT SPECIFICATION

Electrical Specifications

(V

= 12V, VID = [00100] = 1.450V, and T

CC

The • denotes specifications which apply over the full operating temperature range.

Parameter Conditions Min. Typ. Max. Units
Input Supply

UVLO Hysteresis 1.0 V
12V UVLO Rising Edge
12V Supply Current PWM Output Open 20 mA

Internal Voltage Regulator

BYPASS Voltage 4.75 5 5.25 V
BYPASS Capacitor 100 nF

VREF and DAC

Output Voltage See Table 1
Initial Voltage Setpoint

1

Output Temperature Drift T
Line Regulation V

2

Droop
Programmable Droop Range 0 1.25 m Ω
Response Time
Current Mismatch R

VID Inputs

Input LOW current, VID pins V
VID V

IH

VID V

IL

No CPU VID Latency VID = [11111] to PWM low 200 ns

Oscillator

Oscillator Frequency RT = 54.9k Ω
Oscillator Range RT = 137.5k Ω to 13.75 k Ω
Maximum Duty Cycle RT = 137.5k Ω
Minimum LDRV on-time RT = 13.75k Ω

Gate Drive

Gate Drive On-Resistance 1.0
Output Driver Rise & Fall Time See Figure 1, C

Enable/Soft Start

Soft Start Current 10 µA
Enable Threshold ON

Power Good

PWRGD Threshold Logic LOW, V
PWRGD Output Voltage I
PWRGD Delay High → Low 500 µsec
PWRGD Delay Low → High 5 20 ms

OVP and OTP

Output Overvoltage Detect • 2.1 2.3 V
Over Temperature Shutdown 130 140 150 °C
Over Temperature Hysteresis 40 °C

Notes:

1. As measured at the converter’s VFB sense point. For motherboard applications, the PCB layout should exhibit no more than

0.5m Ω trace resistance between the converter’s output capacitors and the CPU. Remote sensing should be used for optimal
performance. Nominal output is offset +25mV vs. VID table.

2. Using the VFB pin for remote sensing of the converter’s output at the load, the converter will be in compliance with AMD

specification of V

DAC

±50mV.

= +25°C using circuit in Figure 2, unless otherwise noted.)

A

8.5 9.6 10.4 V

0.800 1.550 V

I

= 0A, VID = [00100] 1.466 1.475 1.489 V

LOAD

= 0 to 70°C5mV

A

= 11.4V to 12.6V

CC

I

= 52A, R

LOAD

V

= 10mV 100 nsec

out

(A) = R

DS,on

I

= 52A Droop = 1m Ω

LOAD

= 0.4V -60 µA

VID

DROOP

DS,on

= 4.99k Ω

(B),

130 µV

23 mV

5%

2.0 V

0.8 V

440 500 560 kHz
200 2000 kHz

90 %

330 nsec

= 3000pF 20 nsec

L

1.0

OFF

– V

VID

PWRGD

= 4mA 0.4 V

sink

300 350 367 mV

0.4

V

Ω

•

®

4

REV. 1.0.7 2/18/03

PRODUCT SPECIFICATION FAN5098

Gate Drive Test Circuit

3000pF

t

R

90%

t

DT

1.2V

2V

V

OUT

10%

90%

2.5V

t

10%

t

DT

2V

Figure 1. Output Drive Timing Diagram

Table 1. Output Voltage Programming Codes

VID4 VID3 VID2 VID1 VID0 V

11111OFF

111100.800V

111010.825V

111000.850V

110110.875V

110100.900V

110010.925V

110000.950V

101110.975V

101101.000V

101011.025V

101001.050V

100111.075V

100101.100V

100011.125V

100001.150V

011111.175V

011101.200V

011011.225V

011001.250V

010111.275V

010101.300V

010011.325V

010001.350V

001111.375V

001101.400V

001011.425V

001001.450V

000111.475V

000101.500V

000011.525V

000001.550V

HDRV

LDRV

OUT

to CPU

Note: Nominal output is typically offset +25mV from VID table.

REV. 1.0.7 2/18/03 5

FAN5098 PRODUCT SPECIFICATION

Typical Operating Characteristics

(VCC = 12V, VIN = 12V, V

= 1.450V and TA = +25°C using circuit in Figure 2, unless otherwise noted.)

OUT

EFFICIENCY VS. OUTPUT CURRENT

90

85

E* Mode

2 Phase Mode

80

75

70

EFFICIENCY (%)

65

60

010203040

50 60

LOAD CURRENT (A)

HIGH-SIDE GATE DRIVES, NORMAL OPERATION

CH1: HDRVB
CH2: HDRVA
10A Load

TRANSIENT RESPONSE, 20A to 0.25A

CH1: HDRVB
CH2: LDRVB
40A Load

HIGH-SIDE GATE DRIVES, E*-MODE

CH1: HDRVB
CH2: HDRVA
10A Load

ADAPTIVE GATE DELAY

HIGH-SIDE GATE DRIVES, RISE / FALL TIME

CH1: HDRVB
40A Load

LOW-SIDE GATE DRIVES, RISE / FALL TIME

CH1: LDRVB
40A Load

6 REV. 1.0.7 2/18/03