Diodes AT5503 User Manual
18V, 3A Synchronous DC-DC Buck Converter AT5503
Preliminary Datasheet
General Description
The AT5503 is a 500kHz fixed frequency, current
mode, PWM synchronous buck (step-down) DC-DC
converter, capable of driving a 3A load with high
efficiency, excellent line and load regulation. The
AT5503 exhibits high efficiency at light load. The
device integrates N-channel power MOSFET switch
with low on-resistance. Current mode control
provides fast transient response and cycle-by-cycle
current limit.
The AT5503 employs complete protection to ensure
system security, including output Over Voltage
Protection, input Under Voltage Lock Out,
programmable soft-start, Over Temperature
Protection and hiccup mode Short Circuit Protection.
This IC is available in PSOP-8 package.
Features
• Input Voltage Range: 4.5V to 18V
• Fixed 500kHz Frequency
• High Efficiency at Light Load
• Output Current: 3A
• Current Mode Control
• Built-in Over Current Protection
• Built-in Thermal Shutdown Function
• Built-in UVLO Function
• Built-in Over Voltage Protection
• Programmable Soft-start
• Hiccup Mode SCP
Applications
• Monitor
• TV
• STB
• Datacom
PSOP-8
Figure 1. Package Type of AT5503
Mar. 2013 Rev. 1. 0 BCD Semiconductor Manufacturing Limited
1
Preliminary Datasheet
18V, 3A Synchronous DC-DC Buck Converter AT5503
Pin Configuration
MP Package
(PSOP-8)
BS
SW
GND
Figure 2. Pin Configuration of AT5503 (Top View)
IN
1
2
EP
3
4
8
SS
EN
7
COMP
6
FB
5
Pin Description
Pin Number Pin Name Function
Bootstrap pin. A bootstrap capacitor is connected between the
1 BS
2 IN
3 SW
4 GND Ground pin
5 FB
6 COMP
7 EN
8 SS
EP Exposed pad. It should be connected to GND in PCB layout.
BS pin and SW pin. The voltage across the bootstrap
capacitor drives the internal high-side NMOS switch.
Supply input pin. A capacitor should be connected between
the IN pin and GND pin to keep the DC input voltage
constant.
Power switch output pin. This pin is connected to the inductor
and bootstrap capacitor.
Feedback pin. This pin is connected to an external resistor
divider to program the system output voltage. When the FB
pin voltage exceeds 1.1V, the over voltage protection is
triggered. When the FB pin voltage is below 0.3V, the
oscillator frequency is lowered to realize short circuit
protection.
Compensation pin. This pin is the output of the
transconductance error amplifier and the input to the current
comparator. This pin is used to compensate the control loop.
Connect a series RC network from this pin to GND pin. In
some cases, an additional capacitor from this pin to GND pin
is required.
Enable input. EN is a digital input that turns the regulator on
or off. Drive EN high to turn on the regulator, drive it low to
turn off. Pull up with 100kΩ resistor for automatic startup.
Soft-start control input pin. SS controls the soft start period.
Connect a capacitor from SS to GND to set the soft-start
period. A 0.1µF capacitor sets the soft-start period to 15ms.
To disable the soft-start feature, leave SS unconnected.
Mar. 2013 Rev. 1. 0 BCD Semiconductor Manufacturing Limited
2
Preliminary Datasheet
18V, 3A Synchronous DC-DC Buck Converter AT5503
Functional Block Diagram
Figure 3. Functional Block Diagram of AT5503
Ordering Information
Circuit Type G1: Green
Package
MP: PSOP-8
Package
PSOP-8
Temperature
Range
-40 to 85°C
AT5503 -
Blank: Tube
TR: Tape & Reel
Part Number Marking ID
AT5503MP-G1 5503MP-G1 Tube
AT5503MPTR-G1 5503MP-G1 Tape & Reel
Packing
Type
BCD Semiconductor's Pb-free products, as designated with "G1" suffix in the part number, are RoHS compliant
and green.
Mar. 2013 Rev. 1. 0 BCD Semiconductor Manufacturing Limited
3
Preliminary Datasheet
18V, 3A Synchronous DC-DC Buck Converter AT5503
Absolute Maximum Ratings (Note 1)
Parameter Symbol Value Unit
IN Pin Voltage VIN -0.3 to 20 V
EN Pin Voltage VEN -0.3 to VIN V
SW Pin Voltage VSW 21 V
BS Pin Voltage VBS -0.3 to VSW+6 V
FB Pin Voltage VFB -0.3 to 6 V
COMP Pin Voltage V
SS Pin Voltage VSS -0.3 to 6 V
Operating Junction Temperature TJ 150 ºC
Storage Temperature T
Lead Temperature
(Soldering, 10sec)
Thermal Resistance
(Junction to Ambient)
ESD (Human Body Model) V
ESD (Machine Model) VMM 200 V
Note 1: Stresses greater than those listed under “Absolute Maximum Ratings” may cause permanent damage to
the device. These are stress ratings only, and functional operation of the device at these or any other conditions
beyond those indicated under “Recommended Operating Conditions” is not implied. Exposure to “Absolute
Maximum Ratings” for extended periods may affect device reliability.
-0.3 to 6 V
COMP
-65 to 150 ºC
STG
260 ºC
T
LEAD
PSOP-8 60 ºC/W
θ
JA
2000 V
HBM
Recommended Operating Conditions
Parameter Symbol Min Max Unit
Input Voltage VIN 4.5 18 V
Operating Ambient Temperature TA -40 85 ºC
Mar. 2013 Rev. 1. 0 BCD Semiconductor Manufacturing Limited
4
Loading...