Diodes AP3445/L User manual

AP3445/L
EVB User Guide
This EVB user guide contains new product information. Diodes, Inc. reserves the right to modify the product specification without notice.
No liability is assumed as a result of the use of this product. No rights under any patent accompany the sale of the product.
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AP3445/L EVB User Guide
AE Department
1. AP3445/L Revision Information
Date
Revision
Description
Comment
2017/10
V1.0
Initial Release
2. AP3445/L General Description
The AP3445/L is a 2A step-down DC-DC converter. At heavy load, the constant frequency PWM control
performs excellent stability and transient response. No external compensation components are required.
The AP3445/L supports a range of input voltages from 2.7V to 5.5V, allowing the use of a single Li+/Li-
polymer cell, multiple Alkaline/NiMH cell, and other standard power sources. The output voltage is
adjustable from 0.6V to the input voltage. The AP3445/L employs internal power switch and synchronous
rectifier to minimize external part count and realize high efficiency. During shutdown, the input is
disconnected from the output and the shutdown current is less than 1μA. Other key features include
over-temperature and short circuit protection, and under-voltage lockout to prevent deep battery discharge.
The AP3445/L delivers 2A maximum output current while consuming only 55μA of no-load quiescent
current. Ultra-low RDS(ON) integrated MOSFETs and 100% duty cycle operation make the AP3445/L an
ideal choice for high output voltage, high current applications which require a low dropout threshold.
Pulse skip mode allows to maintain high efficiency at light-load conditions.
The AP3445/L is available in TSOT23-6 package.

AP3445/L
EVB User Guide
This EVB user guide contains new product information. Diodes, Inc. reserves the right to modify the product specification without notice.
No liability is assumed as a result of the use of this product. No rights under any patent accompany the sale of the product.
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3. AP3445/L Key Features
Output Current: Up to 2A
Output Voltage: 0.6V to VIN
Input Voltage: 2.7V to 5.5V
55µA (Typ) No Load Quiescent Current
Shutdown Current: <1µA
100% Duty Cycle Operation
1MHz Switching Frequency
Internal Soft Start
No External Compensation Required
Current Limit Protection
Short Circuit Protection
AP3445L: Latch Off Protection
AP3445: Hiccup Mode Protection
Over Voltage Protection
AP3445L: Latch Off Protection
AP3445: Non Latch Off Protection
Thermal Shutdown
4. AP3445/L EV Board Schematic
R1
R2
VIN EN
LX
FB
L1 2.2uH
CIN
22uF
VIN=2.7V to 5.5V
GND
COUT
22uFx2
VOUT=1.8V
ON
AP3445/L
C1
22pF 200kΩ
100kΩ
PG
OFF
R3
100kΩ
5. AP3445/L EV Board Description
AP3445 EV board is suitable evaluation board for the AP3445, a DC/DC converter. The board is targeted
to be used in providing a simple and convenient evaluation environment for the AP3445. Requires parts,
power supply connectors etc. on the board, which makes it easy to be evaluated.

AP3445/L
EVB User Guide
This EVB user guide contains new product information. Diodes, Inc. reserves the right to modify the product specification without notice.
No liability is assumed as a result of the use of this product. No rights under any patent accompany the sale of the product.
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www.diodes.com
October 2018
© Diodes Incorporated
6. AP3445/L EV Board View
7. Setting the Output Voltage of AP3445/L
The output voltage is calculated as below:









2
21
6.0 RRR VOUT
First, select a value for R2, Then, R1 is determined. The output voltage is given by Table 1.
Vo
R1
R2
C3
1.0V
67KΩ
100 KΩ
22pF
1.2V
100KΩ
100 KΩ
22 pF
1.5V
150KΩ
100 KΩ
22 Pf
1.8V
200 KΩ
100 KΩ
22 pF
2.5V
317KΩ
100KΩ
22 pF
2.8V
367KΩ
100KΩ
22 pF
3.3V
450KΩ
100 KΩ
22 pF
Table 1: Resistor selection for output voltage setting

AP3445/L
EVB User Guide
This EVB user guide contains new product information. Diodes, Inc. reserves the right to modify the product specification without notice.
No liability is assumed as a result of the use of this product. No rights under any patent accompany the sale of the product.
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© Diodes Incorporated
8. External Components Selection
(1) Input & output Capacitors (Cin, Cout)
1) For lower output ripple, low ESR is required.
2) Low leakage current needed, X5R/X7R ceramic recommend, multiple capacitor parallel
connection.
3) The Cin and Cout capacitances are greater than 22uF and 44uF respective.
(2) Output voltage programmer resistors (R1, R2)
1) For programmer output voltage
2) For accurate output voltage, 1% tolerance is required.
(3) Inductor (L)
1) Low DCR for good efficiency
2) Inductance saturate current must higher than the output current
3) The recommended inductance is shown in the table below.
Vo
Inductor
Würth PART
1.0V
1.0 uH
74438357010
1.2V
1.0 uH
74438357010
1.5V
1.5 uH
2.2 uH
74438357015
1.8V
1.5 uH
2.2 uH
74438357015
2.5V
2.2 uH
74438357022
2.8V
2.2 uH
74438357022
3.3V
2.2 uH
74438357022

AP3445/L
EVB User Guide
This EVB user guide contains new product information. Diodes, Inc. reserves the right to modify the product specification without notice.
No liability is assumed as a result of the use of this product. No rights under any patent accompany the sale of the product.
5 of 5
www.diodes.com
October 2018
© Diodes Incorporated
9. EV Board BOM List for AP3445/L
Item
Value
Type
Rating
Description
Description
C1
22uF
X5R/X7R,
Ceramic/1206
10V
Input coupling CAP
C3 & C4
22uF
X5R/X7R,
Ceramic/1206
6.8V
Output coupling CAP
L
2.2uH
4030
5.2A
Inductor
Würth PART
74438357022
R1
200K
0805
1%
Voltage set RES*
R2
100K
0805
1%
R3
100K
0805
1%
Power Good RES
C2
22pF
0805
Feedback CAP
U1
AP3445
TSOT23-6
Diodes BCD
*Note: The present value of R1/R2 are based on Vout=1.8V
10. Test Waveforms
Test condition: Vin=5.0V Vo=1.8V Io=2.0A
(Blue: Vout-AC; Yellow: Vsw; Green: IL)