The AP3436/A is a step-down DC-DC converter with integrated
power stage capable of driving up to 3A continuous output current. It
integrates 2 N-channel power MOSFETs with low on-resistance.
Current mode control provides fast transient response and cycle-bycycle current limit.
For AP3436, the regulator adopts current-mode in forced pulse-width
modulation (PWM) mode with 1.25MHz switching frequency
internally, which allows small-sized components, such as capacitors
and inductors. This feature greatly simplifies the design of switchmode power supplies. Under PWM mode, the device remains at the
fixed PWM operation (typical at 1.25MHz), regardless of if the load
current is high or low.
For AP3436A, the regulator operates in either fixed PWM mode or a
pulse-skipping modulation (PSM) mode depending on the different
load conditions. The device can operate at typical 1.25MHz fixed
switching frequency under heavy load condition. At light load, the
regulator enters a PSM mode to minimize the switching loss by
reducing the switching frequency.
The AP3436/A provides EN function. Pulling this pin high statically
enables the device while pulling the pin low statically for longer than
10μs will shut it down.
Under Voltage Lockout is internally set at 2.75V for VCC detection.
The output voltage startup ramp is controlled by the soft start. An
open drain power good signal indicates the output is within 75% to
125% of its nominal voltage.
The AP3436/A is available in U-DFN3030-10 package.
Applications
Desktop & Notebook
Low Voltage, High Density Power System
Consumer Application Such as Set Top Box, LCD Display and
CPE Equipment
Pin Assignments
(Top View)
U-DFN3030-10
Features
Analog Power Input VCC Range: 3.0V to 5.5V
Power Input VIN Range: 1.3V to 5.5V
0.6V Reference Voltage with ±1.5% Precision
2 MOSFETs (Typ 50mΩ) for High Efficiency at 3A Loads
High Efficiency: Up to 95%
Output Current: 3A
Current Mode Control
Built-in Soft Start Function
UV and OV Power Good Output
Built-in UV and OV Protection Function
Built-in Over Current Protection
Built-in Thermal Shutdown Function
Thermally Enhanced 3mm×3mm DFN Package
3A, 1.25MHz High Performance Synchronous Buck Converter
Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green"
and Lead-free.
3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and
<1000ppm antimony compounds.
Thermal Resistance (Junction to Ambient, Simulation)
33
ºC/W
θ
JC
Thermal Resistance (Junction to Case)
3
ºC/W
TJ
Operating Junction Temperature
-40 to +150
ºC
T
STG
Storage Temperature
-65 to +150
ºC
T
LEAD
Lead Temperature (Soldering, 10sec)
+260
ºC
V
HBM
ESD (Human Body Model)
2000
V
VMM
ESD (Machine Model)
200
V
Symbol
Parameter
Min
Max
Unit
VCC
Analog Input Voltage
3.0
5.5
V
VIN
Power Input Voltage
1.3
5.5
V
I
OUT(MAX)
Maximum Output Current
3 – A
V
OUT
Output Voltage
0.8
VIN V TA
Operating Ambient Temperature
-40
+85
ºC
Absolute Maximum Ratings (Note 5)
Note 5: 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 Operati ng Conditions” is not implied. Exposure to “Absolute Maximum Ratings” for extended periods may affect device reliability.
The AP3436/A is a 3A synchronous buck (step-down) converter with two integrated N-channel MOSFETs. For AP3436, the regulator operates in
PWM mode with 1.25MHz switching frequency internally, regardless of if the load current is high or low. For AP3436A, when the load is very light,
the regulator automatically operates in the PSM mode to minimize the switching loss, thus achieving high efficiency at light load. When the load
increases, the regulator automatically switches over to a current-mode PWM operating at nominal 1.25MHz switching frequency.
2. Power On Reset
A Power On Reset (POR) circuitry continuously monitors the supply voltage at VCC pin. Once the rising POR threshold is exceeded, the
AP3436/A sets itself to active state and is ready to accept chip enable command. The rising POR threshold is typically 2.75V.
3. Soft Start
A built-in soft-start is used to prevent surge current from power supply input VIN during turn on (Referring to the Functional Block Diagram). The
error amplifier is a three-input device. Reference voltage V
the non-inverting inputs of the error amplifier. VSS internally ramps up to 0.6V after the soft-start cycle is initiated. The ramp is created digitally, so
the output voltage will follow the VSS signal and ramps up smoothly to its target level.
4. EN Function
The AP3436/A provides Enable Function. Pulling this pin higher than 1.6V statically enables the AP3436/A while pulling the pin lower than 0.8V
statically for longer than 10µs will shutdown the IC.
5. Adjusting Output Voltage
The output voltage is set with a resistor divider from the FB pin. It is recommended to use divider resistors with 1% tolerance or better. Start with a
100kΩ for the resistor R1 and use the following equation to calculate R2. Consider using larger value resistors to improve efficiency at very light
loads. If the values are too high, the regulator is more susceptible to noise and the voltage errors caused by FB input current are noticeable.
6. Short Circuit Protection (SCP)
The AP3436/A has Over Current Protection (OCP) and Under Voltage Protection (UVP) functions.
6.1 OCP Function
The high side switch current is detected during each cycle. During SCP conditions, the output voltage is pulled down and the switch current is
increased. Once the increased high side switching current is detected to trigger the current limit of high side switch, the high side switch will be
immediately turned off and will not be turned on again until the next switching cycle. When over current condition is removed, the AP3436/A will
recover back to normal operation again.
6.2 UVP Function
The FB voltage is also monitored for Under Voltage Protection. The UV threshold is set at 0.2V. The under voltage protection has 65µs triggered
delay. When UVP is triggered, both high side and low side are shutdown immediately. The UVP is a latched function, reset power supply or EN pin
to restart AP3436/A again.
or the internal soft-start voltage VSS whichever is smaller dominates the behavior of
The output voltage is continuously monitored for Over Voltage Protection by FB pin. When it is larger than 1.67 times as setting, the OVP function
is triggered. The Over Voltage Protection has 65µs triggered delay.
When OVP is triggered, both high side and low side are shutdown immediately and the output voltage is discharged by an internal 1kΩ resistor.
8.Power Good
The PGOOD pin output connects an open drain MOSFET. The output is pulled low when the FB voltage enters the fault condition by falling below
75% or rising above 125% of the nominal internal reference voltage. There is a 7% hysteresis on the threshold voltage, so when the FB voltage
rises to the good condition above 82% or falls below 118% of the internal voltage reference the PGOOD output MOSFET is turned off. It is
recommended to use a pull-up resistor between the values of 3kΩ and 100kΩ to a voltage source that is 5V or less.
9. Thermal Shutdown
The device implements an internal thermal shutdown to protect itself if the junction temperature exceeds +160°C. Switching is stopped when the
junction temperature exceeds the thermal trip threshold. Once the die temperature decreases below +140°C, the device reinitiates the soft start
operation. The thermal shutdown hysteresis is +20°C.
First Line: Logo and Marking ID
Second and Third Lines: Date Code
Y: Year
WW: Work Week of Molding
M: Assembly House Code
XX: 7th and 8th Digits of Batch No.
First Line: Logo and Marking ID
Second and Third Lines: Date Code
Y: Year
WW: Work Week of Molding
M: Assembly House Code
XX: 7th and 8th Digits of Batch No.
Ordering Information
Diodes IC’s Pb-free products with "G1" suffix in the part number, are RoHS compliant and green.
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