FAN5099 — Wide Frequency Synchronous Buck PWM & LDO Controller
May 2008
FAN5099 — Wide Frequency Synchronous Buck PWM
& LDO Controller
Features
■
General Purpose PWM Regulator and LDO Controller
■
Input Voltage Range: 3V to 24V
■
Output Voltage Range: 0.8V to 15V
■
V
CC
Description
The FAN5099 combines a high-efficiency pulse-width
modulated (PWM) controller and an LDO (low drop out)
linear regulator controller. The PWM controller is
designed to operate over a wide frequency range (50kHz
to 600kHz) to accommodate a variety of applications.
Synchronous rectification provides high efficiency over a
wide range of load currents. Efficiency is further
enhanced by using the low-side MOSFET’s R
DS(ON)
to
sense current. In addition, the capability to operate at low
switching frequencies provides opportunities to boost
power supply efficiency by reducing switching losses and
gain cost savings using low-cost materials, such as pow-
dered iron cores, on the output inductor.
Both the linear and PWM regulator soft-start are con-
trolled by a single external capacitor, to limit in rush cur-
rent from the supply when the regulators are first
enabled. Current limit for PWM is also programmable.
The FAN5099’s ability to handle wide input voltage
ranges makes this controller suitable for power solutions
in a wide range of applications involving conversion input
voltages from Silver box, battery, and adapters. The
PWM regulator employs a summing-current-mode con-
trol with external compensation to achieve fast load tran-
sient response and provide system design optimization.
FAN5099 is offered in both industrial temperature grade
(-40°C to +85°C) as well as commercial temperature
grade (-10°C to +85°C).
■
■
■
■
■
■
■
■
– 5V
– Shunt Regulator for 12V Operation
Support for Ceramic Cap on PWM Output
Programmable Current Limit for PWM Output
Wide Programmable Switching Frequency Range
(50kHz to 600kHz)
R
DS(ON)
Current Sensing
Internal Synchronous Boot Diode
Soft-Start for both PWM and LDO
Multi-Fault Protection with Optional Auto-restart
16-Pin TSSOP Package
Applications
■
High-Efficiency (80+) Computer Power Supplies
■
PC/Server Motherboard Peripherals
– V
CC
_MCH (1.5V), V
DDQ
(1.5V) and
V
TT_GTL
(1.25V)
■
Power Supply for
– FPGA, DSP, Embedded Controllers, Graphic Card
Processor, and Communication Processors
■
High-Power DC-to-DC Converters
Related Application Notes
■
AN-6020 FAN5099 Component Calculation and
Simulation Tools
■
AN-6005 Synchronous Buck MOSFET Loss
Calculations with Excel Model
Ordering Information
Part Number
FAN5099MTCX
FAN5099EMTCX
FAN5099MX
FAN5099EMX
Operating Temperature Range
-10°C to +85°C
-40°C to +85°C
-10°C to +85°C
-40°C to +85°C
Package
16-Lead TSSOP
16-Lead TSSOP
16-Lead SOIC
16-Lead SOIC
Packing Method
Tape and Reel
Tape and Reel
Tape and Reel
Tape and Reel
Qty/Reel
2500
2500
2500
2500
All standard Fairchild Semiconductor products are RoHS compliant and many are also “GREEN” or going green. For Fairchild’s
definition of “green” please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
Contact Fairchild sales for availability of other package options.
© 2006 Fairchild Semiconductor Corporation
FAN5099 Rev. 1.1.5
www.fairchildsemi.com
FAN5099 — Wide Frequency Synchronous Buck PWM & LDO Controller
Typical Application
Figure 1. Typical Application Diagram
© 2006 Fairchild Semiconductor Corporation
FAN5099 Rev. 1.1.5
www.fairchildsemi.com
2
FAN5099 — Wide Frequency Synchronous Buck PWM & LDO Controller
Pin Configuration
Figure 2. Pin Assignment
Pin Description
Pin No. Pin Name
1
2
3
FBLDO
R(T)
ILIM
Pin Description
LDO Feedback.
This node is regulated to V
REF
.
Oscillator Set Resistor.
This pin provides oscillator switching frequency adjustment. By plac-
ing a resistor (RT) from this pin to GND, the nominal 50kHz switching frequency is increased.
Current Limit.
A resistor from this pin to GND sets the current limit.
Soft-Start.
A capacitor from this pin to GND programs the slew rate of the converter and the
LDO during initialization. It also sets the time by which the converter delays when restarting
after a fault occurs. SS has to reach 1.2V before fault shutdown feature is enabled. The LDO
is enabled when SS reaches 2.2V.
COMP.
The output of the error amplifier drives this pin.
Feedback.
This pin is the inverting input of the internal error amplifier. Use this pin, in combi-
nation with the COMP pin, to compensate the feedback loop of the converter.
Enable.
Enables operation when pulled to logic high. Toggling EN resets the regulator after a
latched fault condition. This is a CMOS input whose state is indeterminate if left open and
needs to be properly biased at all times.
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 available.
Switching Node.
Return for the high-side MOSFET driver and a current sense input. Connect
to source of high-side MOSFET and drain of low-side MOSFET.
High-Side Gate Drive Output.
Connect to the gate of the high-side power MOSFETs. This
pin is also monitored by the adaptive shoot-through protection circuitry to determine when the
high-side MOSFET is turned off.
Bootstrap Supply Input.
Provides a boosted voltage to the high-side MOSFET driver.
Connect to bootstrap capacitor as shown in Figure 1.
Power Ground.
The return for the low-side MOSFET driver. Connect to source of low-side
MOSFET.
Low-Side Gate Drive Output.
Connect to the gate of the low-side power MOSFETs. This pin
is also monitored by the adaptive shoot-through protection circuitry to determine when the
lower MOSFET is turned off.
Ramp Resistor.
A resistor from this pin to VIN sets the ramp amplitude and provides voltage
feed-forward.
V
CC
.
Provides bias power to the IC and the drive voltage for LDRV. Bypass with a ceramic
capacitor as close to this pin as possible. This pin has a shunt regulator which draws current
when the input voltage is above 5.6V.
Gate Drive for the LDO.
Turned off (low) until SS is greater than 2.2V.
4
SS
5
6
COMP
FB
7
EN
8
9
AGND
SW
10
HDRV
11
12
BOOT
PGND
13
LDRV
14
R(RAMP)
15
16
VCC
GLDO
© 2006 Fairchild Semiconductor Corporation
FAN5099 Rev. 1.1.5
www.fairchildsemi.com
3
FAN5099 — Wide Frequency Synchronous Buck PWM & LDO Controller
Absolute Maximum Ratings
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be opera-
ble above the recommended operating conditions and stressing the parts to these levels is not recommended. In addi-
tion, extended exposure to stresses above the recommended operating conditions may affect device reliability. The
absolute maximum ratings are stress ratings only. Absolute maximum ratings apply individually only, not in combina-
tion. Unless otherwise specified, all other voltages are referenced to AGND.
Parameter
VCC to GND
BOOT to GND
BOOT to SW
SW to GND
HDRV to SW
LDRV to PGND
All Other Pins
Maximum Shunt Current
Human Body Model
(Mil Std. 883E, Method 3015.7)
Charged Device Model
(EIA/JESD22C101-A)
Continuous
Continuous
Transient (t < 100ns, f < 500kHz)
Continuous
Transient (t < 50ns, f < 500kHz)
Continuous
Transient (t < 50ns, f < 500kHz)
Continuous
Transient (t < 40ns, f < 500kHz)
Continuous
Transient (t < 40ns, f < 500kHz)
Continuous
Min.
-0.3
-0.5
-0.5
-2.5
-0.5
-3.0
-0.5
-2.5
-0.5
-2.5
-0.3
Max.
6.0
33
35
6.0
33.0
35.0
6.0
6.0
V
CC
+ 0.3
150
Unit
V
V
V
V
V
V
V
V
V
V
V
V
mA
3.5
kV
1.8
Electrostatic Discharge (ESD) Protection Level
Thermal Information
Symbols
T
STG
T
L
Storage Temperature
Lead Soldering Temperature, 10 Seconds
Vapor Phase, 60 Seconds
Infrared, 15 Seconds
P
D
θ
JC
θ
JA
Notes:
1. Junction-to-ambient thermal resistance,
θ
JA
, is a strong function of PCB material, board thickness, thickness and
number of copper planes, number of vias used, diameter of vias used, available copper surface, and attached heat
sink characteristics.
Power Dissipation, T
A
= 25°C
Thermal Resistance – Junction-to-Case
Thermal Resistance – Junction-to-Ambient
(1)
37
100
Parameter
Min.
-65
Typ.
Max.
+150
+300
+215
+220
715
Unit
°C
°C
°C
°C
mW
°C/W
°C/W
© 2006 Fairchild Semiconductor Corporation
FAN5099 Rev. 1.1.5
www.fairchildsemi.com
4
FAN5099 — Wide Frequency Synchronous Buck PWM & LDO Controller
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.
Symbols
V
CC
T
A
T
J
Parameter
Supply Voltage
Ambient Temperature
Junction Temperature
Conditions
V
CC
to GND
Commercial
Industrial
Min.
4.5
-10
-40
Typ.
5.0
Max.
5.5
+85
+85
+125
Unit
V
°C
°C
°C
Electrical Characteristics
Unless otherwise noted, V
CC
= 5V, T
A
= 25°C, using the circuit in Figure 1. The ‘•’ denotes that the specifications apply
to the full ambient operating temperature range.
(2,3)
Symbol
Supply Current
I
VCC
I
VCC(SD)
I
VCC(OP)
V
SHUNT
UVLO(H)
UVLO(L)
Parameter
V
CC
Current (Quiescent)
V
CC
Current (Shutdown)
V
CC
Current (Operating)
V
CC
Voltage
(4)
Rising V
CC
UVLO Threshold
Falling V
CC
UVLO Threshold
V
CC
UVLO Threshold
Hysteresis
Conditions
HDRV, LDRV Open
EN = 0V, V
CC
= 5.5V
EN = 5V, V
CC
= 5.0V,
Q
FET
= 20nC, f
SW
= 200kHz
Sinking 1mA to 100mA at V
CC
Pin
•
•
•
•
Min.
2.6
Typ.
3.2
200
10
Max.
3.8
400
15
5.9
Unit
mA
μA
mA
V
V
V
V
5.4
4.00
3.60
4.25
3.75
0.5
Under-Voltage Lockout (UVLO)
4.50
4.00
Soft-Start
I
SS
Current
PWM Protection Enable
Threshold
R(T) = 25.5KΩ ± 1%
f
OSC
Frequency
Operating Frequency Range
ΔV
RAMP
Ramp Amplitude
(Peak-to-Peak)
Minimum On Time
Reference
V
REF
Reference Voltage
(Measured at FB Pin)
Current Amplifier Reference
(at SW node)
T
A
= 0°C to 70°C
T
A
= -40°C to 85°C
•
•
10
2.2
1.2
μA
V
V
V
LDOSTART
LDO Start Threshold
V
SSOK
Oscillator
240
60
40
R(RAMP) = 330KΩ
f = 200kHz
790
788
300
80
50
360
100
600
kHz
kHz
kHz
kHz
V
ns
R(T) = 199KΩ ± 1%
R(T) = Open
0.4
200
800
800
160
810
812
mV
mV
mV
Continued on the following page...
© 2006 Fairchild Semiconductor Corporation
FAN5099 Rev. 1.1.5
www.fairchildsemi.com
5
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