FAN2108 — TinyBuck™, 3-24V Input, 8A, High-Efficiency, Integrated Synchronous Buck Regulator
August 2009
FAN2108 — TinyBuck™
3-24V Input, 8A, High-Efficiency, Integrated Synchronous
Buck Regulator
Features
Wide Input Voltage Range: 3V-24V
Wide Output Voltage Range: 0.8V to 80% V
IN
8A Output Current
Programmable Frequency Operation: 200KHz to
600KHz
Over 95% Peak Efficiency
Integrated Schottky Diode on Low-side MOSFET
Boosts Efficiency
Internal Bootstrap diode
Power-Good Signal
Pre-Bias Startup
Accepts Ceramic Capacitors on Output
External Compensation for Flexible Design
Input Under-Voltage Lockout
Programmable Current Limit
Under-Voltage, Over-Voltage, and Thermal
Shutdown Protections
Internal Soft-Start
5x6mm, 25-Pin, 3-Pad MLP Package
Description
The FAN2108 TinyBuck™ is a highly efficient, small
footprint, 8A, synchronous buck regulator.
The FAN2108 contains both synchronous MOSFETs
and a controller/driver with optimized interconnects in
one package, which enables designers to solve high-
current requirements in a small area with minimal
external components.
External compensation, programmable switching
frequency, and current limit features allow design
optimization and flexibility.
The summing current mode modulator uses lossless
current sensing for current feedback and over-current
protection. Voltage feedforward helps operation over a
wide input voltage range.
Fairchild’s advanced BiCMOS power process,
combined with low-R
DS(ON)
internal MOSFETs and a
thermally efficient MLP package, provide the ability to
dissipate high power in a small package.
Output over-voltage, under-voltage, and thermal
shutdown protections help protect the device from
damage during fault conditions. FAN2108 prevents pre-
biased output discharge during startup in point-of-load
applications.
Applications
Servers
Point-of-Load Regulation
High-End Computing Systems
Graphics Cards
Battery-Powered Equipment
Set-Top Boxes
Related Application Notes
AN-8022 — TinyCalc™ Calculator
Ordering Information
Part Number
FAN2108MPX
FAN2108EMPX
Operating
Temperature Range
-10°C to 85°C
-40°C to 85°C
Package
Molded Leadless Package (MLP) 5x6mm
Molded Leadless Package (MLP) 5x6mm
Eco
Status
Green
Green
Packing
Method
Tape and Reel
Tape and Reel
For Fairchild’s definition of Eco Status, please visit:
http://www.fairchildsemi.com/company/green/rohs_green.html.
© 2008 Fairchild Semiconductor Corporation
FAN2108 • Rev. 1.0.1
www.fairchildsemi.com
FAN2108 — TinyBuck™, 3-24V Input, 8A, High-Efficiency, Integrated Synchronous Buck Regulator
Typical Application
Figure 1. Typical Application Diagram
Block Diagram
Figure 2. Block Diagram
© 2008 Fairchild Semiconductor Corporation
FAN2108 • Rev. 1.0.1
www.fairchildsemi.com
2
FAN2108 — TinyBuck™, 3-24V Input, 8A, High-Efficiency, Integrated Synchronous Buck Regulator
Pin Configuration
Figure 3. MLP 5x6mm Pin Configuration (Bottom View)
Pin Definitions
Pin #
P1, 6-12
P2, 2-5
P3, 21-23
1
13
14
15
16
17
18
19
20
24
25
Name
SW
VIN
PGND
BOOT
PGOOD
EN
VCC
AGND
ILIM
R(T)
FB
COMP
NC
RAMP
Description
Switching Node.
Power Input Voltage.
Connect to the main input power source.
Power Ground.
Power return and Q2 source.
High-Side Drive BOOT Voltage.
Connect through capacitor (C
BOOT
) to SW. The IC
includes an internal synchronous bootstrap diode to recharge the capacitor on this pin to
V
CC
when SW is LOW.
Power-Good Flag.
An open-drain output that pulls LOW when FB is outside a ±10% range
of the reference. PGOOD does not assert HIGH until the fault latch is enabled.
ENABLE.
Enables operation when pulled to logic HIGH or left open. Toggling EN resets the
regulator after a latched fault condition. This input has an internal pull-up when the IC is
functioning normally. When a latched fault occurs, EN is discharged by a current sink.
Input Bias Supply for IC.
The IC’s logic and analog circuitry are powered from this pin.
Analog Ground.
The signal ground for the IC. All internal control voltages are referred to
this pin. Tie this pin to the ground island/plane through the lowest impedance connection.
Current Limit.
A resistor (R
ILIM
) from this pin to AGND can be used to program the current-
limit trip threshold lower than the default setting.
Oscillator Frequency.
A resistor (R
T
) from this pin to AGND sets the PWM switching
frequency.
Output Voltage Feedback.
Connect through a resistor divider to the output voltage.
Compensation.
Error amplifier output. Connect the external compensation network
between this pin and FB.
No Connect.
This pin is not used.
Ramp Amplitude.
A resistor (R
RAMP
) connected from this pin to V
IN
sets the ramp amplitude
and provides voltage feedforward functionality.
© 2008 Fairchild Semiconductor Corporation
FAN2108 • Rev. 1.0.1
www.fairchildsemi.com
3
FAN2108 — TinyBuck™, 3-24V Input, 8A, High-Efficiency, Integrated Synchronous Buck Regulator
Absolute Maximum Ratings
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be
operable above the recommended operating conditions and stressing the parts to these levels is not recommended.
In addition, extended exposure to stresses above the recommended operating conditions may affect device
reliability. The absolute maximum ratings are stress ratings only.
Parameter
VIN to PGND
VCC to AGND
BOOT to PGND
BOOT to SW
SW to PGND
All other pins
ESD
Continuous
AGND=PGND
Conditions
Min.
Max.
28
6
35
Unit
V
V
V
V
V
V
V
kV
-0.3
-0.5
-5
-0.3
Human Body Model, JEDEC JESD22-A114
Charged Device Model, JEDEC JESD22-C101
2
2.5
Transient (t < 20ns, f < 600KHz)
6.0
24.0
30
V
CC
+0.3
Recommended Operating Conditions
The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended
operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not
recommend exceeding them or designing to absolute maximum ratings.
Symbol
V
CC
V
IN
T
A
T
J
f
Parameter
Bias Voltage
Supply Voltage
Ambient Temperature
Junction Temperature
Switching Frequency
Conditions
VCC to AGND
VIN to PGND
FAN2108MPX
FAN2108EMPX
Min.
4.5
3
-10
-40
Typ.
5.0
Max.
5.5
24
+85
+85
+125
600
Unit
V
V
°C
°C
°C
kHz
Thermal Information
Symbol
T
STG
T
L
T
VP
T
I
θ
JC
θ
J-PCB
P
D
Storage Temperature
Lead Soldering Temperature, 10 Seconds
Vapor Phase, 60 Seconds
Infrared, 15 Seconds
P1 (Q2)
Thermal Resistance: Junction-to-Case
P2 (Q1)
P3
Thermal Resistance: Junction-to-Mounting Surface
Power Dissipation, T
A
=25°C
(1)
(1)
Parameter
Min.
-65
Typ.
Max.
+150
+300
+215
+220
Unit
°C
°C
°C
°C
°C/W
°C/W
°C/W
°C/W
4
7
4
35
2.8
W
Note:
1. Typical thermal resistance when mounted on a four-layer, two-ounce PCB, as shown in Figure 24. Actual results
are dependent on mounting method and surface related to the design.
© 2008 Fairchild Semiconductor Corporation
FAN2108 • Rev. 1.0.1
www.fairchildsemi.com
4
FAN2108 — TinyBuck™, 3-24V Input, 8A, High-Efficiency, Integrated Synchronous Buck Regulator
Electrical Specifications
Electrical specifications are the result of using the circuit shown in Figure 1 unless otherwise noted.
Symbol
Power Supplies
I
CC
V
CC
Current
Parameter
Conditions
SW=Open, FB=0.7V, V
CC
=5V,
f
SW
=600KHz
Shutdown: EN=0, V
CC
=5V
Rising V
CC
Hysteresis
R
T
=50KΩ
R
T
=24KΩ
Min.
Typ. Max. Unit
8
7
4.1
4.3
300
255
540
300
600
50
12
10
4.5
mA
µA
V
mV
V
UVLO
Oscillator
f
t
ON
V
RAMP
t
OFF
Reference
V
FB
V
CC
UVLO Threshold
Frequency
Minimum On-Time
(2)
345
660
65
KHz
KHz
ns
V
Ramp Amplitude, peak-to–peak
Minimum Off-Time
(2)
16V
IN
, 1.8V
OUT
, R
T
=30KΩ,
R
RAMP
=200KΩ
0.53
100
150
806
805
ns
mV
mV
dB
MHz
Reference Voltage
(see Figure 4 for
Temperature Coefficient)
(2)
(2)
FAN2108MPX, 25°C
FAN2108EMPX, 25°C
794
795
80
800
800
85
15
Error Amplifier
G
BW
V
COMP
I
SINK
I
SOURCE
I
BIAS
DC Gain
Gain Bandwidth Product
Output Voltage
Output Current, Sourcing
Output Current, Sinking
FB Bias Current
V
CC
=5V, V
COMP
=2.2V
V
CC
=5V, V
COMP
=1.2V
V
FB
=0.8V, 25°C
R
ILIM
Open at 25°C
(see Circuit
Description)
V
CC
=5V
12
0.4
1.5
0.8
-850
2.2
1.2
-650 -450
3.2
V
mA
mA
nA
Protection and Shutdown
I
LIM
I
ILIM
T
TSD
T
HYS
V
OVP
V
UVLO
V
FLT
V
FLT_HYS
Soft-Start
t
SS
t
EN
V
OUT
to Regulation (T0.8)
Fault Enable/SSOK (T1.0)
Frequency=600KHz
5.3
6.7
ms
ms
Current Limit
I
LIM
Current
Over-Temperature Shutdown
Over-Temperature Hysteresis
Over-Voltage Threshold
Under-Voltage Shutdown
Fault Discharge Threshold
Fault Discharge Hysteresis
Internal IC Temperature
Two Consecutive Clock Cycles
16 Consecutive Clock Cycles
Measured at FB Pin
Measured at FB Pin (V
FB
~500mV)
110
68
12
-11
15
-10
+155
+30
115
73
250
250
121
78
18
-9
A
µA
°C
°C
%V
OUT
%V
OUT
mV
mV
Note:
2. Specifications guaranteed by design and characterization; not production tested.
© 2008 Fairchild Semiconductor Corporation
FAN2108 • Rev. 1.0.1
www.fairchildsemi.com
5
京公网安备 11010802033920号
EEWORLD
