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AP65353
3A, 18V, 650kHz ADAPTIVE COT STEP-DOWN CONVERTER
Description
The AP65353 is an adaptive constant on-time mode synchronous buck converter providing high efficiency, excellent transient response and high DC output accuracy for low-voltage regulation in digital TV and monitor.
Pin Assignments ( Top View )
The constant-on-time control scheme handles wide input/output voltage ratios and provides low external component count. The internal proprietary circuit enables the device to adopt both low equivalent series resistance (ESR) output capacitors, such as SP-CAP or POSCAP and ultra-low ESR ceramic capacitors.
EN 1 FB 2
Exposed Pad
8 VIN 7 BST
The adaptive on-time control supports seamless transition between continuous conduction mode (CCM) at higher load conditions and discontinuous conduction mode (DCM) at lighter load conditions.
DCM allows AP65353 to maintain high efficiency at light load conditions. The AP65353 also features programmable soft-start, UVLO, OTP, OVP and OCP to protect the circuit.
VREG5 3 SS 4
9 SO-8EP
6 SW 5 PGND
This IC is available in SO-8EP package.
Applications
• Gaming Consoles • Flat Screen TV Sets and Monitors • Set-Top Boxes • Home Audio • Consumer Electronics • Network Systems • Green
Notes:
1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS), 2011/65/EU (RoHS 2) & 2015/863/EU (RoHS 3).compliant. 2. See https://www.diodes.com/quality/lead-free/ 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.
AP65353
Document number: DS37925 Rev. 3 - 4
1 of 15 www.diodes.com
March 2021
© Diodes Incorporated
OBSOLETE – PART DISCONTINUED
Typical Applications Circuit
INPUT VIN 12V
C1 20μF
OFF
C4 8.2nF
8 IN
ON 1
EN
4 SS
7 BST
6 SW AP65353
2 FB 3 5 VREG5 GND
C5 L1 0.1µF 1.5μH
R1 8.25kΩ
R2
C3
22.1kΩ
1µF
OUTPUT VOUT 1.05V
C2 44μF
Figure 1 Typical Application Circuit
AP65353
Pin Descriptions
Pin Name
Pin Number
EN
1
FB
2
VREG5
3
SS
4
SW
6
BST VIN PGND
7 8 5, 9 (Exposed Pad)
Function
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. EN can be safely connected to VIN directly for automatic startup.
Feedback Input. FB senses the output voltage and regulates it. Drive FB with a resistive voltage divider connected to it from the output voltage.
Internal power supply output pin to connect an additional capacitor. Connect a 1μF (typical) capacitor as close as possible to the VREG5 and PGND. This pin is not active when EN is low.
Soft-start control input pin. SS controls the soft start period. Connect a capacitor from SS to PGND to set the soft-start period.
Power Switching Output. SW is the switching node that supplies power to the output. Connect the output LC filter from SW to the output load. Note that a capacitor is required from SW to BST to power the high-side switch.
Bootstrap pin. A bootstrap capacitor is connected between the BST pin and SW pin. The voltage across the bootstrap capacitor drives the internal high-side NMOS switch. A 0.1μF (typical) capacitor is required for proper operation.
Supply input. A capacitor should be connected between the VIN pin and PGND pin to keep the DC input voltage constant.
Power ground and GND. Exposed pad must be connected to as large of PGND plane as possible for maximum thermal performance.
AP65353
Document number: DS37925 Rev. 3 - 4
2 of 15 www.diodes.com
March 2021
© Diodes Incorporated
OBSOLETE – PART DISCONTINUED
Functional Block Diagram
AP65353
EN
1
Logic
UVLO Control
SS
4 Soft Start SS
Se
+
0.6V
Internal Reference
2 FB
+ -
SS
+
Min Off Time
S
Q
R
Q
5V
Vcc
Regulator
8 VIN
3 VREG5
OCP SW Ref
5V
7 BST
SW
On Time Compute
Digital Control Logic
One Shot
SS
6 SW
VIN
Frequency Lock Loop
5, 9 PGND
Figure 2 Functional Block Diagram
AP65353
Document number: DS37925 Rev. 3 - 4
3 of 15 www.diodes.com
March 2021
© Diodes Incorporated
OBSOLETE – PART DISCONTINUED
AP65353
Absolute Maximum Ratings (Note 4) (@TA = +25°C, unless otherwise specified.)
Symbol
Parameter
VIN
Supply Voltage
VREG5
VREG5 Pin Voltage
VSW
Switch Node Voltage
VBST
Bootstrap Voltage
VFB
Feedback Voltage
VEN
Enable/UVLO Voltage
VSS
Soft-start PIN
VPGND
PGND Pin Voltage
TST
Storage Temperature
TJ
Junction Temperature
TL
Lead Temperature
ESD Susceptibility (Note 5)
HBM
Human Body Model
MM
Machine Model
Rating -0.3 to 20 -0.3V to +6.0 -1.0 to VIN +0.3 -0.3 to VSW +6.0 -0.3V to +6.0 -0.3V to VIN -0.3V to +6.0 -0.3 to 0.3 -65 to +150
+160 +260
2 200
Unit V V V V V V V V °C °C °C
kV V
Notes:
4. Stresses greater than the 'Absolute Maximum Ratings' specifie.