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ACE724C
18V 2.5A Synchronous PFM/PWM Buck Converter
Description
The ACE724C is a high efficiency current‐mode synchronous, 18V/2.5A buck converter. Its input voltage
ranges from 3.5V to 18V and it provides an adjustable regulated output voltage from 0.923V to 15V while
delivering up to 2A of output current.
The internal synchronous switches increase efficiency and eliminate the need for an external Schottky
diode. The switching frequency is set to 340KHz. And the ACE724C will automatically switch between
PFM and PWM mode based on the load current, thus to enhance the converter efficiency at light load.
ACE724C consists of many protection block such as UVLO, input voltage over voltage protection to
stand much higher input voltage spike, thermal protection and output short circuit protection.
Features
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Adjustable Output Voltage, Vfb=0.923V
Maximum output current is 2.5A
Range of operation input voltage: Max 18V
UVLO: 3.4V (typ.)
Withstand input voltage spike >30V
Standby current: 1mA (typ.)
Operating current at zero load: 1.2mA (typ.)
Line regulation: 0.1%/V (typ.)
Load regulation: 10mV (typ.)
High efficiency, up to 95%
Environment Temperature: -20℃~85℃
Application
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Set-top-box
Consumer Electronic Device for automobile
LCD Monitor and LCD TV
Portable DVD
ADSL Modem, WLAN router
Other 12V or double cell Li-ion battery powered device
Absolute Maximum Ratings
Parameter
Symbol Value Unit
Input voltage
Ambien temperature
Package thermal resistance
SOP-8
ESOP-8
Max Operation junction temperature
30
V
TA
-20~85
℃
ΘJC
45
10
125
℃/W
>2000
V
Tj
ESD (HBM)
Storage temperature range
TS
℃
-40~125 ℃
Note: Exceed these limits to damage to the device. Exposure to absolute maximum rating conditions may affect device reliability.
VER 1.2
1
ACE724C
18V 2.5A Synchronous PFM/PWM Buck Converter
Packaging Type
SOP-8 / ESOP-8
1
8
2
7
3
6
4
5
SOP-8/ESOP-8 Description
Function
1
BST
2
VIN
3
SW
High side power transistor gate drive boost input
Power input, the input capacitor should be placed as close to VIN and
GND pin as possible
Power switching node to connect inductor
4
GND
Ground
5
FB
6
COMP
7
EN
8
SS
Feedback input with reference voltage set to 0.923
Compensation node. A serial RC connected to this pin is required to
maintain the Buck converter control loop stable
Enable input. Setting it to high level or connecting to Vin via a resistor
may turn on the chip, while setting it to ground level will turn off the chip
Soft-start node. Connecting a 0.1uF capacitor to ground make the Buck
converter output rise smoothly
Ordering information
Selection Guide
ACE724C XX +
H
Halogen - free
Pb - free
FM : SOP-8
IM : ESOP-8
VER 1.2
2
ACE724C
18V 2.5A Synchronous PFM/PWM Buck Converter
Block Diagram
Recommended Work Conditions
Item
Input voltage range
Value Unit
Max. 18 V
Operating junction temperature -20~125
O
C
PFM at Light Load
Zero Load Operating Current vs. Vin
VER 1.2
3
ACE724C
18V 2.5A Synchronous PFM/PWM Buck Converter
Typical Application
ACE724C
* When Vin is as low as 5V, Cc is recommended to be 100pf, but not needed when Vin larger than 5V.
Electrical Characteristics
(Vin=12V, TA=25℃)
Parameter
Symbol
Test Conditions
Min
Typ
Input voltage range
VDD
Feedback voltage
Vref
Vin=12V, Ven=5V
0.90 0.923 0.946
V
UVLO Voltage
VUVLO
Vin H->L, Iout=0.5A
3.4
V
Feedback leakage current
Ifb
Quiescent current
Iq
Line regulation
3.5
Max
Unit
18
V
0.1
0.4
uA
Active, Vfb=1V, No switching
1.1
1.5
mA
Shutdown, Vin=8V
6
10
uA
LnReg
Vin=5V to 12V
0.1
%/V
Load regulation
LdReg
Iout=0.1 to 2A
0.02
%/A
Switching
Fsoc
Ven=2V, Vin=12V
340
KHz
PMOS Rdson
RdsonP
130
mΩ
NMOS Rdson
RdsonN
110
mΩ
Peak current limit
Llimit
3.8
A
EN high threshold
Venh
EN low threshold
Venl
Input over-voltage
Vovp
Over temperature proection
TSD
1
1.5
2
0.5
Ven=2V
18
V
V
160
℃
VER 1.2
4
ACE724C
18V 2.5A Synchronous PFM/PWM Buck Converter
Typical performance characteristics
(Vin=12V, Vout=3.3V, L=10uH, Cin=10uF, Cout=22uF, TA=25℃, unless otherwise stated)
VER 1.2
5
ACE724C
18V 2.5A Synchronous PFM/PWM Buck Converter
Typical performance characteristics
(Vin=12V, Vout=3.3V, L=10uH, Cin=10uF, Cout=22uF, TA=25℃, unless otherwise stated)
Functional Descriptions
Loop Operation
The ACE724C is a wide input range, high‐efficiency, DC‐to‐DC step‐down switching regulator, capable
of delivering up to 2.5A of output current, integrated with a 110m
synchronous MOSFET, eliminating
the need for external diode. It uses a PWM current‐mode control scheme. An error amplifier integrates
error between the FB signal and the internal reference voltage. The output of the integrator is then
compared to the sum of a current‐sense signal and the slope compensation ramp. This operation
generates a PWM signal that modulates the duty cycle of the power MOSFETs to achieve regulation for
output voltage.
Current Limit
There is a cycle‐by‐cycle current limit on the high‐side MOSFET of 3.8A (typ). When the current flowing
out of SW exceeds this limit, the high‐side MOSFET turns off and the synchronous rectifier turns on.
Unlike the traditional method of current limiting by limiting the voltage at the compensation pin, which
usually has large variation due to duty cycle variance, this type of peak current limiting scheme provides a
relatively more accurate limit for output current, thereby lowering the requirements for system design.
Light Load Operation
Traditionally, a fixed current mode constant frequency PWM DC‐DC regulator always switches even
when the output load is small. When energy is shuffling back and forth through the power MOSFETs,
power is lost due to the finite RDSONs of the MOSFETs and parasitic capacitances. At light load, this loss
is prominent and efficiency is therefore very low. ACE724C employs a proprietary control scheme that
improves efficiency in this situation by enabling the device into a power save mode during light load,
thereby extending the range of high efficiency operation.
VER 1.2
6
ACE724C
18V 2.5A Synchronous PFM/PWM Buck Converter
Faster Transient Response
Normally, people use 3.3nF and 5.6Kohm RC for compensation to keep the loop stable. However, if one
needs to have faster load transient response, 3.3nF and 8.5Kohm is recommended.
Component selection
When setting up the ACE724C for different output voltage, please use following recommended
component value for the best performance.
VOUT(V) COUT(µF) L(µH)
8
22*2
22
5
22*2
15
3.3
22*2
10
2.5
22*2
6.8
1.8
22*2
4.7
1.2
22*2
3.3
Thermal consideration
ACE724C is high efficiency Buck converter, which means it consumes very few power when converting
the high voltage to low voltage. However, when output power is very large, like 5V/2A, the output power is
as high as 10W, a heat dissipation path is strongly recommended to be routed on PCB. ACE724C has
two different SOP8 package. For the normal SOP8, the heat is conducted out via Pin 4 (GND), so the
heat dissipation route on PCB should be connected to the Pin 4 of the chip. If ESOP8 is selected, the heat
dissipation copper area should be exposed and connected to the exposed pad underneath the chip body.
When output power is larger than 10W, the ESOP8 package is recommended.
VER 1.2
7
ACE724C
18V 2.5A Synchronous PFM/PWM Buck Converter
Packing Information
SOP-8
VER 1.2
8
ACE724C
18V 2.5A Synchronous PFM/PWM Buck Converter
Packing Information
ESOP-8
HEAT SLUG
(BTM)
NOTES: ALL DIMENSIONS REFER TO JEDEC STANDARD MS-012 AA DO NOT INCLUDE MOLD
FLASH OR PROTRUSIONS.
BASE METAL
SECTION B-B
VER 1.2
9
ACE724C
18V 2.5A Synchronous PFM/PWM Buck Converter
Notes
ACE does not assume any responsibility for use as critical components in life support devices or systems
without the express written approval of the president and general counsel of ACE Electronics Co., LTD.
As sued herein:
1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and shoes failure to perform when properly used in
accordance with instructions for use provided in the labeling, can be reasonably expected to result in
a significant injury to the user.
2. A critical component is any component of a life support device or system whose failure to perform can
be reasonably expected to cause the failure of the life support device or system, or to affect its safety
or effectiveness.
ACE Technology Co., LTD.
http://www.ace-ele.com/
VER 1.2
10
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