FAN6520B Fairchild Semiconductor, FAN6520B Datasheet

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FAN6520B

Manufacturer Part Number
FAN6520B
Description
Single Synchronous Buck PWM Controller
Manufacturer
Fairchild Semiconductor
Datasheet
©2006 Fairchild Semiconductor Corporation
FAN6520B Rev. 1.0.3
FAN6520B
Single Synchronous Buck PWM Controller
Features
Applications
Ordering Information
FAN6520BM
FAN6520BMX
FAN6520BIM
FAN6520BIMX
Accepts 1.5V to 5V for V
Output Range 0.8V to V
– 0.8V Internal Reference
– ±1.5% Over Line Voltage and Temperature
Drives N-Channel MOSFETs
Simple Single-Loop Control Design
– Voltage-Mode PWM Control
Fast Transient Response
– High-Bandwidth Error Amplifier
– Full 0% to 100% Duty Cycle
Small Converter Size
– 300kHz Fixed Frequency Oscillator
– Internal Soft-Start
– 8-Lead SOIC
Power Supplies for PC Subsystems and Peripherals
MCH, GTL, and AGP Supplies
Cable Modems, Set Top Boxes, and DSL Modems
DSP, Memory
Low-Voltage Distributed Power Supplies
ACPI Power Control
5V Input DC-DC Regulator
Part Number
IN
IN
Temperature Range
–40°C to 85°C
–40°C to 85°C
0°C to 70°C
0°C to 70°C
1
Description
The FAN6520B makes simple work out of implementing
a complete control and protection scheme for a DC-DC
stepdown converter.
Designed to drive N-channel MOSFETs in a synchro-
nous buck topology, the FAN6520B integrates the con-
trol, output adjustment, and monitoring functions into a
single 8-lead package.
The FAN6520B is easy to use, employs a single feed-
back loop, and voltage-mode control with fast transient
response. The output voltage can be precisely regulated
to as low as 0.8V, with a maximum tolerance of ±1.5%
over temperature and line voltage variations. A fixed fre-
quency oscillator reduces design complexity, while bal-
ancing typical application cost. The error amplifier
features a 15MHz gain-bandwidth product and an 8V/µs
slew rate which enables high converter bandwidth for
fast transient performance. The resulting PWM duty
cycles range from 0% to 100%.
The FAN6520B is rated for operation from 0° to +70°C
with the FAN6520BI rated from –40° to +85°C.
Package
SOIC-8
SOIC-8
SOIC-8
SOIC-8
Tape and Reel
Tape and Reel
Packing
Rails
Rails
February 2006
www.fairchildsemi.com

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FAN6520B Summary of contents

Page 1

... FAN6520B integrates the con- trol, output adjustment, and monitoring functions into a single 8-lead package. The FAN6520B is easy to use, employs a single feed- back loop, and voltage-mode control with fast transient response. The output voltage can be precisely regulated to as low as 0.8V, with a maximum tolerance of ±1.5% over temperature and line voltage variations. A fi ...

Page 2

... Switch Node Input. Connect as shown in Figure 1. The SW pin provides return for the high-side bootstrapped driver sense point for the adaptive shoot-thru protection. FAN6520B Rev. 1.0.3 BOOT HDRV 2 7 COMP/SD FAN6520B GND LDRV 4 5 VCC FAN6520BM 8-pin SOIC Package Pin Function Description 2 www.fairchildsemi.com ...

Page 3

... Typical Application +5V VCC C R PULLUP COMP/SD VCC COMP/SD FB 0.8V FAN6520B Rev. 1.0.3 BOOT HDRV 2 VCC SW 8 FAN6520B Q2 LDRV 4 GND Figure 1. Typical Application POR / SOFT START PWM ERROR AMP OSC Figure 2. Functional Block Diagram 3 Vin = 1. BOOT C BOOT ...

Page 4

... T = 25° Thermal Resistance – Junction to Case Thermal Resistance – Junction to Ambient Recommended Operating Conditions Parameter Supply Voltage VCC Ambient Temperature ( Junction Temperature ( FAN6520B Rev. 1.0.3 Min. – 0.5 – 0.5 – 3 Min. – Conditions Min. VCC to PGND 4.5 FAN6520B 0 FAN6520BI – ...

Page 5

... Notes: 1. All limits at operating temperature extremes are guaranteed by design, characterization and statistical quality control. 2. Specifications guaranteed by design/characterization (not production tested ensure shutdown, COMP/SD pin should be held below 400mV while sinking 6mA of current. FAN6520B Rev. 1.0.3 Symbol Conditions I HDRV, LDRV open • ...

Page 6

... C and C may each represent numerous IN OUT physical capacitors. Locate the FAN6520B as close as possible to Q1 and Q2 MOSFETs. The circuit traces for the MOSFETs’ gate and source connections from the FAN6520B must be sized to handle peak current. Vin FAN6520B Q1 HDRV L OUT ...

Page 7

... OUT compared E/A 1. The compensation network consists of the error amplifier (internal to the FAN6520B) and the imped- ance networks Z pensation network is to provide a closed loop transfer function with the highest 0dB crossing fre- quency (F margin is the difference between the closed loop ...

Page 8

... Given a sufficiently fast control loop design, the FAN6520B 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 cur- rent level ...

Page 9

... --------------------- - BOOT V BOOT FAN6520B Rev. 1.0.3 where Q is the total gate charge of the high-side MOS- G FET, and high-side MOSFET drive. To prevent loss of gate drive, the bootstrap capacitance should be at least 50 times greater than the C secutive cycles, then LDRV is turned on for ~1.6µs to charge the bootstrap capacitor ...

Page 10

... Losses in a MOSFET are the sum of its switching (P and conduction (P ) losses. COND In typical applications, the FAN6520B converter's output voltage is low with respect to its input voltage, therefore the lower MOSFET (Q2) is conducting the full load cur- rent for most of the cycle. Therefore choose a MOSFET ...

Page 11

... Low-Side Losses Q2, however, switches on or off with its parallel shottky diode conducting, therefore V DS proportional Q2’s switching losses are negligible DS and we can select Q2 based on R FAN6520B Rev. 1.0.3 Conduction losses for Q2 are given by: P COND (16) where R DS(ON) highest operating junction temperature and and Q ...

Page 12

... Mosfet, N, 30V, 94A, 6.8m , DPAK R1 Resistor, 1.00K , 1%, 0603 R2 Resistor, 3.74K , 1%, 0603 R3 Resistor, 120 , 5%, 0603 R4 Resistor, 2.00K , 1%, 0603 R5 Resistor, 10K , 5%, 0603 R6 Resistor, 1.5 , 5%, 0805 U1 IC, Single Synchronous Buck PWM, SOIC 8 Contact factory for the latest bill of materials. FAN6520B Rev. 1.0.3 D1 BOOT HDRV FAN6520B LDRV 4 ...

Page 13

... Dimensional Outline Drawing 4.90 0.10 3.81 8 6.00 1 PIN ONE INDICATOR (0.33) 1.27 1.75 MAX 1.45+0.05 -0.20 0.15+0.10 (R0.10) (R0.10 0.70 0.20 (1.04) DETAIL A SCALE: 2:1 FAN6520B Rev. 1.0 3.90 0.10 1.00 4 0.51 0.35 0. LAND PATTERN RECOMMENDATION C 0.10 C -0.05 0. 0.25 GAGE PLANE 0.36 SEATING PLANE 13 4.75 1.27 0.50 3.81 SEE DETAIL A NOTES: UNLESS OTHERWISE SPECIFIED A) THIS PACKAGE CONFORMS TO JEDEC MS-012, VARIATION AA, ISSUE C, DATED MAY 1990. ...

Page 14

... PRODUCT STATUS DEFINITIONS Definition of Terms Datasheet Identification Advance Information Preliminary No Identification Needed Obsolete FAN6520B Rev. 1.0.3 PowerSaver™ ISOPLANAR™ PowerTrench LittleFET™ QFET MICROCOUPLER™ QS™ MicroFET™ QT Optoelectronics™ ...

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