Document
ADVANCED INFORMATION
AP3405
600mA Step-down DC/DC Converter with Synchronous Rectifier
Description
The AP3405 is a 2.0MHz fixed frequency, current mode, PWM synchronous buck (step-down) DC-DC converter, capable of driving a 600mA load with high efficiency, excellent line and load regulation. The high efficiency is easily configured by using an inductor, resistors and capacitors as the external components. Current mode control provides fast transient response and cycle-by-cycle current limit.
The AP3405 employs complete protection to ensure system security, including input Undervoltage Lockout, Over-Temperature Protection and hiccup mode Short Circuit Protection.
Pin Assignments
(Top View) Pin 1 Mark
NC 1 NC 2 AGND 3
EP
This IC is available in U-DFN2020-8 package.
PGND 4
8 EN 7 FB 6 VIN 5 SW
U-DFN2020-8 (Type E)
Features
High-Efficiency Buck Power Converter Input Voltage Range: 2.3V to 5.5V Output Voltage Range: 0.7V to 5.5V Fixed 2.0MHz Oscillator Frequency Built-in Soft-Start Time Built-in Overcurrent Protection Built-in Thermal Shutdown Function Built-in UVLO Function Hiccup Mode SCP Output Current: 600mA Package: U-DFN2020-8 (Type E) Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2) Halogen and Antimony Free. “Green” Device (Note 3)
Applications
Post DC-DC Voltage Regulation Mobile Phones and Wearable Devices
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.
Typical Applications Circuit
VIN
CIN 4.7μF
ON/OFF
L 2.2μH
6 VIN
5 SW
AP3405 FB 7
8 EN
AGND 3 PGND 4
R1 240KΩ
R2 120KΩ
VOUT 1.8V
Cff 22pF
COUT 10μF
AP3405
Document number: DS38093 Rev. 1 - 2
1 of 9 www.diodes.com
January 2016
© Diodes Incorporated
ADVANCED INFORMATION
AP3405
Pin Descriptions
Pin Number 1,2 3 4 5 6 7 8
Pin Name NC
AGND PGND
SW VIN FB EN
Function
No connection
Signal Ground Pin
Power Ground Pin
Power switch output pin. This pin is connected to the inductor. Supply power input pin. A capacitor should be connected between VIN pin and GND - to keep the input voltage constant. Feedback pin. This pin is connected to an external resistor divider to program the system output voltage. Control input pin. EN is a digital input that turns the regulator on or off. Drive EN high to turn the regulator on. Drive low to turn the regulator off.
Functional Block Diagram
EN 8
Slope Compensation
Shutdown Comparator
Bias Generator
Soft Start
Oscillator
OCP Comparator
UVLO
Current Sensing
PWM Comparator
Control Logic
Buffer & Dead Time
Control Logic
7 FB
Error Amplifier
Reverse Inductor Current Comparator
Bandgap Reference
Vin OVP Comparator
VIN 6
5 SW
4 PGND
3 AGND
AP3405
Document number: DS38093 Rev. 1 - 2
2 of 9 www.diodes.com
January 2016
© Diodes Incorporated
ADVANCED INFORMATION
AP3405
Absolute Maximum Ratings (@TA = +25°C, unless otherwise specified.) (Note 4)
Note:
Symbol
Parameter
Rating
Unit
VIN VIN Input Voltage VSW SW Pin Voltage
-0.3 to 6.5 -0.3 to VIN + 0.3
V V
VEN VFB ISW PD TSTG
EN Pin Input Voltage VFB Pin Voltage SW Pin Output Current Power Dissipation (Standard Land Pattern) Storage Temperature Range
-0.3 to 6.5 -0.3 to 6.5
1 640 -55 to +125
V V A mW °C
VHBM
ESD (Human Body Model)
2,000
V
4. 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.
Recommended Operating Conditions (@TA = +25°C, unless otherwise specified.)
Symbol VIN TA
Parameter Input Voltage Operating Ambient Temperature
Min 2.3 -40
Max 5.5 +85
Unit V °C
AP3405
Document number: DS38093 Rev. 1 - 2
3 of 9 www.diodes.com
January 2016
© Diodes Incorporated
ADVANCED INFORMATION
AP3405
Electrical Characteristics (VIN = VEN = 3.6V (VOUT ≤ 2.6V), VIN = VEN = VOUT+1V (VOUT > 2.6V), unless otherwise specified.
Specification with standard typeface are for TA = +25°C, and those in boldface type apply over the full operating temperature range (TA = -40°C to +85°C))
Symbol
VIN
IDD ISTDB VUVLO VHYS VENH VENL VFB IFBH IFBL RONH RONL ILIMH fOSC DMAX TOTSD THYS tSS
Parameter
Input Voltage
Supply Current Standby Current Input UVLO Threshold Input UVLO Hysteresis EN Active Threshold Voltage EN Shutdown Threshold Voltage Feedback Voltage FB High Input Current FB Low Input Current High-Side Switch On-Resistance Low-Side Switch On-Resistance SW Current Limit Oscilla.