ACE735E - ACE Technology Co., LTD.

ACE735E
36V Input Standoff Voltage, 1.5A Step-Down Converter
Description
The ACE735E is a wide input range, high-efficiency, and high frequency DC-to-DC step-down switching
regulator, capable of delivering up to 1.5A of output current. With a fixed switching frequency of 650KHz,
this current mode PWM controlled converter allows the use of small external components, such as
ceramic input and output caps, as well as small inductors. ACE735E also employs a proprietary control
scheme that switches the device into a power save mode during light load, thereby extending the range of
high efficiency operation. An OVP function protects the IC itself and its downstream system against input
voltage surges. With this OVP function, the IC can stand off input voltage as high as 42V, making it an
ideal solution for industrial applications such as smart meters as well as automotive applications.
In automotive systems, power comes from the battery, with its voltage typically between 9V and 24V.
Including cold crank and double battery jump-starts, the minimum input voltage may be as low as 4V and
the maximum up to 36V, with even higher transient voltages. With these high input voltages, linear
regulators cannot be used for high supply currents without overheating the regulator. Instead, high
efficiency switching regulators such as ACE735E must be used to minimize thermal dissipation.
ACE735E is available in a space-saving SOT23-6 package.
Features
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Wide Input Operating Range from 4V to 36V
Standoff Input Voltage: 38V
High Efficiency at 12V In 5V Out: Up to 91%
High Efficiency PFM mode at light load
Capable of Delivering 1.5A
No External Compensation Needed
Current Mode control
Logic Control Shutdown
Thermal shutdown and UVLO
Available in SOT23-6 Package
Application
 Smart Meters
 Industrial Applications
 Automotive Applications
VER 1.1
1
ACE735E
36V Input Standoff Voltage, 1.5A Step-Down Converter
Absolute Maximum Rating
Parameter
Value
IN Voltage
–0.3V to 42V
SW ,EN Voltage
–0.3V to VIN+0.3
BST Voltage
–0.3V to SW+6V
FB Voltage
–0.3V to 6V
SW to ground current
Internally limited
Operating Temperature Range
–40°C to 85°C
Storage Temperature Range
.–55°C to 150°C
Thermal Resistance
SOT23-6
θJA
220
θJC
110
°C/W
(Note: Exceeding these limits may damage the device. Exposure to absolute maximum rating conditions for long periods may affect device reliability.)
Typical Application
VER 1.1
2
ACE735E
36V Input Standoff Voltage, 1.5A Step-Down Converter
Packaging Type
SOT-23-6
Function
SOT-23-6 Description
1
BST
Bootstrap pin. Connect a 10nF capacitor from this pin to SW.
2
GND
Ground
3
FB
4
EN
5
IN
6
SW
Feedback Input. Connect an external resistor divider from the
output to FB and GND to set VOUT
Enable pin for the IC. Drive this pin high to enable the part, low to
disable.
Supply Voltage. Bypass with a 10μF ceramic capacitor to GND.
Inductor Connection. Connect an inductor between SW and the
regulator output.
Ordering information
ACE735E XX +
H
Halogen - free
Pb - free
GM : SOT-23-6
VER 1.1
3
ACE735E
36V Input Standoff Voltage, 1.5A Step-Down Converter
Block Diagram
Electrical Characteristics
VIN=VEN=5, TA=25℃
Parameter
Input Standoff Voltage
Conditions
Min
Typ
Max
38
Input Voltage Range
Unit
V
4
36
V
Input UVLO
Rising, Hysteresis=140mV
3.8
V
Input OVP
Rising, Hysteresis=1.3V
38
V
Input Supply Current
VFB=0.85V
0.6
mA
6
μA
FB Feedback Voltage
0.8
FB Input Current
0.01
V
μA
Switching Frequency
650
KHz
Input Shutdown Current
Maximum Duty Cycle
Fold-Back Frequency
%
90
VFB=0 V
60
KHz
High side Switch On Resistance lSW =200mA
300
mΩ
High side Switch Current Limit
2.5
A
SW Leakage Current
VIN=12V,VSW=0,EN=GND
EN Input Current
VIN=12V,VEN=5V
EN Input Low Voltage
Rising, Hysteresis=100mV
Thermal Shutdown
Hysteresis=40℃
0.8
10
μA
1
5
μA
1.1
1.4
V
150
℃
VER 1.1
4
ACE735E
36V Input Standoff Voltage, 1.5A Step-Down Converter
FUNCTIONAL DESCRIPTIONS
Loop Operation
The ACE735E is a wide input range, high-efficiency, DC-to-DC step-down switching regulator, capable
of delivering up to 1.5A of output current, integrated with a 300mΩ high side MOSFET. 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.
Light Load Operation
Traditionally, a fixed 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. ACE735E 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.
APPLICATION INFORMATION
Setting Output Voltages
Output voltages are set by external resistors. The FB threshold is 0.8V.
RTOP = RBOTTOM x [(VOUT / 0.8) - 1]
Inductor Selection
The peak-to-peak ripple is limited to 30% of the maximum output current. This places the peak current
far enough from the minimum overcurrent trip level to ensure reliable operation while providing enough
current ripples for the current mode converter to operate stably. In this case, for 1.5A maximum output
current, the maximum inductor ripple current is 500 mA. The inductor size is estimated as following
equation:
LIDEAL=(VIN(MAX)-VOUT)/IRIPPLE*DMIN*(1/FOSC) Therefore, for VOUT=5V,
The inductor values is calculated to be L = 13μH. Chose 10μH or 15μH
For VOUT =3.3V,
The inductor values is calculated to be L = 9.2μH. Chose 10μH
Output Capacitor Selection
For most applications a nominal 22μF or larger capacitor is suitable. The ACE735E internal
compensation is designed for a fixed corner frequency that is equal to
For example, for VOUT=5V, L=15μH, COUT=22μF.
The output capacitor keeps output ripple small and ensures control-loop stability. The output capacitor
must also have low impedance at the switching frequency. Ceramic, polymer, and tantalum capacitors are
suitable, with ceramic exhibiting the lowest ESR and high-frequency impedance. Output ripple with a
ceramic output capacitor is approximately as follows:
VRIPPLE = IL(PEAK)[1 / (2π x fOSC x COUT)]
If the capacitor has significant ESR, the output ripple component due to capacitor ESR is as follows:
VRIPPLE(ESR) = IL(PEAK) x ESR
VER 1.1
5
ACE735E
36V Input Standoff Voltage, 1.5A Step-Down Converter
Input Capacitor Selection
The input capacitor in a DC-to-DC LED Driver reduces current peaks drawn from the battery or other
input power source and reduces switching noise in the controller. The impedance of the input capacitor at
the switching frequency should be less than that of the input source so high-frequency switching currents
do not pass through the input source.The output capacitor keeps output ripple small and ensures
control-loop stability
Dimming Control
VOUT (V)
8
5
3.3
COUT (μF)
22
22
22
COUT (μF)
15 to 22
10 to 15
6.8 to 10
TYPICAL CHARACTERISTICS
VER 1.1
6
ACE735E
36V Input Standoff Voltage, 1.5A Step-Down Converter
VER 1.1
7
ACE735E
36V Input Standoff Voltage, 1.5A Step-Down Converter
VER 1.1
8
ACE735E
36V Input Standoff Voltage, 1.5A Step-Down Converter
Packing Information
SOT-23-6
VER 1.1
9
ACE735E
36V Input Standoff Voltage, 1.5A Step-Down 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 1.1
10