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Электронный компонент: FAN6520AMX

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www.fairchildsemi.com
REV. 1.0.2 8/26/04
Features
Output Range 0.8V to V
IN
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
Lossless, Programmable Over-current Protection
Uses Upper MOSFET's R
DS(ON)
Small Converter Size
300kHz Fixed Frequency Oscillator
Internal Soft-Start
8-Lead SOIC
Applications
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
General Description
The FAN6520A 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 synchronous
buck topology, the FAN6520A integrates the control, output
adjustment, monitoring and protection functions into a single
8-lead package.
The FAN6520A is easy to use, employs a single feedback
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 frequency oscillator
reduces design complexity, while balancing typical
application cost. The error amplifier features a 15MHz gain-
bandwidth product and an 8V/s slew rate which enables
high converter bandwidth for fast transient performance.
The resulting PWM duty cycles range from 0% to 100%.
The IC monitors the drop across the upper MOSFET and
inhibits PWM operation appropriately to protect against
over-current conditions. This approach simplifies the
implementation and improves efficiency by eliminating
the need for a current sense resistor.
The FAN6520A is rated for operation from 0 to +70C with
the FAN6520AI rated from 40 to +85C.
FAN6520A
Single Synchronous Buck PWM Controller
2
REV. 1.0.2 8/26/04
FAN6520A
PRODUCT SPECIFICATION
Pin Configuration
FAN6520AM 8-pin SOIC Package
Pin Definitions
Pin #
Pin Name
Pin Function Description
1
BOOT
Bootstrap Supply Input.
Provides a boosted voltage to the high-side MOSFET driver.
Connect to bootstrap capacitor as shown in Figure 1.
2
HDRV
High Side Gate Drive Output.
Connect to the gate of the high-side power MOSFET(s).
This pin is also monitored by the adaptive shoot-through protection circuitry to determine
when the upper MOSFET has turned off.
3
GND
Ground.
The signal and power ground for the IC. Tie this pin to the ground island/plane
through the lowest impedance connection available. Connect directly to source of low-side
MOSFET(s).
4
LDRV
Low Side Gate Drive Output.
Connect to the gate of the low-side power MOSFET(s).
This pin is also monitored by the adaptive shoot-through protection circuitry to determine
when the lower MOSFET has turned off.
5
VCC
VCC.
Provides bias power to the IC and the drive voltage for LDRV. Bypass with a ceramic
capacitor as close to this pin as possible.
6
FB
Feedback.
This pin is the inverting input of the internal error amplifier. Use this pin, in
combination with the COMP/OCSET pin, to compensate the voltage-control feedback loop
of the converter.
7
COMP/
OCSET/SD
COMP/OCSET/SD.
This is a multiplexed pin. During operation, the output of the error
amplifier drives this pin. During a short period of time following power-on reset (POR), this
pin is used to determine the over-current threshold of the converter. Pulling COMP/OCSET
to a level below 0.8V disables the controller. Disabling the controller causes the oscillator
to stop, the HDRV and LDRV outputs to be held low, and the soft-start circuitry to re-arm.
8
SW
Switch Node Input.
Connect as shown in Figure 1. The SW pin provides return for the
high-side bootstrapped driver, is a sense point for the adaptive shoot-thru protection, and
is used for monitoring the drop across Q1's R
DS(ON)
for current limit.
FAN6520A
1
2
3
4
8
7
6
5
SW
COMP/OCSET/SD
FB
VCC
BOOT
HDRV
GND
LDRV
3
REV. 1.0.2 8/26/04
FAN6520A
PRODUCT SPECIFICATION
Typical Application
Figure 1. Typical Application
Figure 2. Functional Block Diagram
FB
FAN6520A
VCC
+V
OUT
Q2
COMP/OCSET
R
S
GND
LDRV
SW
HDRV
BOOT
5
3
4
8
2
1
6
7
Q1
C
HF
R
OFFSET
R
OCSET
C
F
R
F
C
I
C
BOOT
D
BOOT
C
BULK
C
VCC
+5V
L
OUT
C
OUT
INHIBIT
PWM
FB
0.8V
ERROR

+
AMP
COMP/OCSET
20A
OSC
GATE
CONTROL
LOGIC
OC
GND
LDRV
SW
HDRV
BOOT
PWM
POR / SOFT START
VCC
SAMPLE
& HOLD
VCC

+
+
4
REV. 1.0.2 8/26/04
FAN6520A
PRODUCT SPECIFICATION
Absolute Maximum Ratings
Absolute maximum ratings are the values beyond which the device may be damaged or have its useful life
impaired. Functional operation under these conditions is not implied.
Thermal Information
Recommended Operating Conditions
Parameter
Min.
Max.
Units
VCC to GND
6
V
VBOOT to GND
15
V
HDRV (V
BOOT
V
SW
)
6
V
LDRV
0.5
6
V
SW to PGND
Continuous
0.5
6
V
Transient ( t < 50nsec, F < 500kHz)
3
7
V
All other pins
5.5
V
Parameter
Min.
Typ.
Max.
Units
Storage Temperature
65
150
C
Lead Soldering Temperature, 10 seconds
300
C
Vapor Phase, 60 seconds
215
C
Infrared, 15 seconds
220
C
Power Dissipation (P
D
), T
A
= 25C
715
mW
Thermal Resistance Junction to Case
JC
40
C/W
Thermal Resistance Junction to Ambient
JA
140
C/W
Parameter
Conditions
Min.
Typ.
Max.
Units
Supply Voltage VCC
VCC to PGND
4.5
5
5.5
V
Ambient Temperature (T
A
)
FAN6520A
0
70
C
FAN6520AI
40
85
C
Junction Temperature (T
J
)
40
125
C
PRODUCT SPECIFICATION
FAN6520A
REV. 1.0.2 8/26/04
5
Electrical Specifications
VCC = 5V, and TA = 25C using circuit in Figure 1 unless otherwise noted.
The denotes specifications which apply over the full operating temperature range.
Notes:
1. All limits at operating temperature extremes are guaranteed by design, characterization and statistical quality control.
2. AC specifications guaranteed by design/characterization (not production tested).
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Units
Supply Current
VCC Current
I
VCC
HDRV, LDRV open
1.5
2.4
3.8
mA
Power-On Reset
Rising VCC POR Threshold
POR
4.00
4.22
4.45
V
VCC POR Threshold Hysteresis
170
mV
Oscillator
Frequency
F
OSC
FAN6520A
250
300
340
kHz
FAN6520AI
230
300
340
kHz
Ramp Amplitude
V
OSC
1.5
Vp-p
Reference
Reference Voltage
V
REF
T
A
= 0 to 70C
788
800
812
mV
FAN6520AI
780
800
820
mV
Error Amplifier
DC Gain
88
dB
Gain Bandwidth Product
GBWP
15
MHz
Slew Rate
S/R
8
V/s
Gate Drivers
HDRV pull-up resistance
R
HUP
2.5
HDRV pull-down resistance
R
HDN
2.0
LDRV pull-up resistance
R
LUP
2.5
LDRV pull-down resistance
R
LDN
1.0
Protection/Disable
OCSET Current Source
I
OCSET
FAN6520A
17
20
22
A
FAN6520AI
14
20
24
A
Disable Threshold
V
DISABLE
800
mV