ACE721E - ACE Technology Co., LTD.

ACE721E
1A, 1.5MHz Step-Down Converter
Description
The ACE721E is a high-efficiency, DC-to-DC step-down switching regulator, capable of delivering up to
1A of output current. The devices operate from an input voltage range of 2.6V to 5.5V and provide output
voltages from 0.6V to VIN, making the ACE721E ideal for low voltage power conversions. Running at a
fixed frequency of 1.5MHz allows the use of small inductance value and low DCR inductors, thereby
achieving higher efficiencies. Other external components, such as ceramic input and output caps, can
also be small due to higher switching frequency, while maintaining exceptional low noise output voltages.
Built-in EMI reduction circuitry makes this converter ideal power supply for RF applications. Internal
soft-start control circuitry reduces inrush current. Short-circuit and thermal-overload protection improves
design reliability.
Features
•
•
•
•
•
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Up to 96% Efficiency
Up to 1A Max Output Current
1.5MHz Frequency
Light Load operation
Internal Compensation and Soft-Start
Tiny SOT-23-5 DFN2x2-6 Package
Application
•
•
•
•
•
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MIDs, Tablet PC
Set Top Boxes
USB ports/Hubs
Hot Swaps
Cellphones
Blue tooth.
Absolute Maximum Rating
Parameter
Value
IN, SW, FB, EN Voltage
-0.3V~6.5V
SW to ground current
Internally limited
Maximum Power Dissipation
400mW
Operating Temperature Range
-40°C~85°C
Storage Temperature Range
-55°C~150°C
SOT23-5
400mW
DFN2x2x6L
606mW
Thermal Resistance
Note: Exceed these limits to damage to the device. Exposure to absolute maximum rating conditions may affect device reliability.
VER 1.3
1
ACE721E
1A, 1.5MHz Step-Down Converter
Typical Application
Efficiency Vs IOUT
1.8V/1A 1.5MHz Step-Down Converter
Packaging Type
SOT-23-5
DFN2*2-6L
SOT-23-5 DFN2*2-6 Description
1
2
EN
2
1/5/7
GND
3
4
SW
4
3
IN
5
6
FB
Function
Enable pin for the IC. Drive this pin high to enable the part, low to
disable.
Ground
Inductor Connection. Connect an inductor Between SW and the
regulator output.
Supply Voltage. Bypass with a 10μF ceramic capacitor to GND
Feedback Input. Connect an external resistor divider from the
output to FB and GND to set the output to a voltage between 0.6V
and VIN
Ordering information
ACE721E XX + H
Halogen - free
Pb - free
BN : SOT-23-5
MN: DFN2*2-6
VER 1.3
2
ACE721E
1A, 1.5MHz Step-Down Converter
Block Diagram
Electrical Characteristics
VIN=VEN=5, TA=25℃
Parameter
Input Voltage Range
Conditions
Min
Typ
Max
Unit
6
V
2.31
2.45
V
40
70
uA
1
uA
0.612
V
2.6
Input UVLO
Rising, Hysteresis=90mV
Input Supply Current
VFB =0.65V
2.31
Input Shutdown Current
FB Feedback
Voltage
VIN =2.5 to 5V
0.588
FB Input Current
0.6
0.01
Output Voltage Range
0.6
uA
Load Regulation
VOUT =1.8V, IOUT From 0.2A to 0.4A
0.1
V
%
Line Regulation
VIN =2.7 to 5.5V
0.2
%V
1.5
MHz
Switching Frequency
VIN
NMOS Switch On Resistance
ISW =200mA
200
mΩ
PMOS Switch On Resistance
ISW =200mA
280
mΩ
PMOS Switch Current Limit
SW Leakage Current
1.5
VIN=5.5V,VSW=0 or 5.5V,EN= GND
EN Input Current
EN Input Low Voltage
EN Input High Voltage
A
10
uA
1
uA
0.4
V
1.5
VER 1.3
V
3
ACE721E
1A, 1.5MHz Step-Down Converter
Typical Characteristics
(Typical values are at TA=25°C unless otherwise specified)
Efficiency Vs IOUT
IOUT (A)
Efficiency Vs IOUT
IOUT (A)
Efficiency Vs IOUT
IOUT (A)
Load Transient Response
VOUT VS IOUT
IOUT(mA)
VOUT Vs VIN
VIN=3.6V,VOUT=1.2V,IOUT=0.2A to 1A
VIN(V)
Load Transient Response
Load Transient Response
Heavy Load Switching Waveform
VIN=3.6V, VOUT=1.8V, IOUT=0.2A to 1A
VIN=5V, VOUT=3.3V, IOUT=0.5A to 1A
VIN=3.6V, VOUT=1.8V, IOUT=0.5A
VER 1.3
4
ACE721E
1A, 1.5MHz Step-Down Converter
Typical Characteristics
(Typical values are at TA=25°C unless otherwise specified)
Startup Waveform with EN Turn on
Startup Waveform with EN Tied to IN
Startup Waveform with EN Turn on
VIN=5V, VOUT=3.3V Into 1A Resistive
VIN=5V, VOUT=3.3V Into 1A Resistive
VIN=5V, VOUT=3.3V 1A Resistive Load
Startup Waveform with EN Tied to IN
Short Circuit Response
Short Circuit Recovery
VIN=5V, VOUT=1.8V Into NoLoad
VIN=5V, VOUT=3.3V
VIN=5V,VOUT=3.3V
VER 1.3
5
ACE721E
1A, 1.5MHz Step-Down Converter
FUNCTION DESCRIPTION
The ACE721E high efficiency switching regulator is a small, simple, DC-to-DC step-down converter
capable of delivering up to 1A of output current. The device operates in pulse-width modulation (PWM) at
1.5MHz from a 2.6V to 5.5V input voltage and provides an output voltage from 0.6V to VIN, making the
ACE721E ideal for on-board post-regulation applications. An internal synchronous rectifier improves
efficiency and eliminates the typical Schottky free-wheeling diode. Using the on resistance of the internal
high-side MOSFET to sense switching currents eliminates current-sense resistors, further improving
efficiency and cost.
Loop Operation
ACE721E uses a PWM current-mode control scheme. An open-loop comparator compares the
integrated voltage-feedback signal against the sum of the amplified current-sense signal and the slope
compensation ramp. At each rising edge of the internal clock, the internal high-side MOSFET turns on
until the PWM comparator terminates the on cycle. During this on -time, current ramps up through the
inductor, sourcing current to the output and storing energy in the inductor. The current mode feedback
system regulates the peak inductor current as a function of the output voltage error signal. During the off
cycle, the internal high –side P-channel MOSFET turns off, and the internal low-side N-channel MOSFET
turns on. The inductor releases the stored energy as its current ramps down while still providing current to
the output.
Current Sense
An internal current-sense amplifier senses the current through the high-side MOSFET during on time
and produces a proportional current signal, which is used to sum with the slope compensation signal. The
summed signal then is compared with the error amplifier output by the PWM comparator to terminate the
on cycle.
Current Limit
There is a cycle-by-cycle current limit on the high-side MOSFET. When the current flowing out of SW
exceeds this limit, the high-side MOSFET turns off and the synchronous rectifier turns on. ACE721E
utilizes a frequency fold-back mode to prevent overheating during short-circuit output conditions. The
device enters frequency fold-back mode when the FB voltage drops below 200mV, limiting the current to
IPEAK and reducing power dissipation. Normal operation resumes upon removal of the short-circuit
condition.
Soft-start
ACE721E has an internal soft-start circuitry to reduce supply inrush current during startup conditions.
When the device exits under-voltage lockout (UVLO), shutdown mode, or restarts following a
thermal-overload event, the l soft-start circuitry slowly ramps up current available at SW.
VER 1.3
6
ACE721E
1A, 1.5MHz Step-Down Converter
UVLO and Thermal Shutdown
If IN drops below 2.4V, the UVLO circuit inhibits switching. Once IN rises above 2.6V, the UVLO clears,
and the soft-start sequence activates. Thermal-overload protection limits total power dissipation in the
device. When the junction temperature exceeds TJ=+160°C, a thermal sensor forces the device into
shutdown, allowing the die to cool. The thermal sensor turns the device on again after the junction
temperature cools by 15°C, resulting in a pulsed output during continuous overload conditions. Following
a thermal-shutdown condition, the soft-start sequence begins.
DESIGN PROCEDURE
Setting Output Voltages
Output voltages are set by external resistors. The FB threshold is 0.6V.
RTOP = RBOTTOM x [(VOUT / 0.6) - 1]
Input Capacitor and Output Capacitor Selection
The input capacitor in a DC-to-DC converter 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. Input ripple with a ceramic capacitor is approximately as follows:
VRIPPLE = IL(PEAK)[1 / (2π x fOSC x CIN)]
If the capacitor has significant ESR, the output ripple component due to capacitor ESR is as follows:
VRIPPLE(ESR) = IL(PEAK) x ESR
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.
Inductor Selection
A reasonable inductor value (LIDEAL) can be derived from the following:
LIDEAL = [2(VIN) x D(1 - D)] / IOUT x fOSC
PCB LAYOUT GUIDE
PCB layout is very important to achieve stable operation. It is highly recommended to duplicate EVB
layout for optimum performance.
If change is necessary, please follow these guidelines and take Figure for reference.
1) Keep the path of switching current short and minimize the loop area formed by input cap, high-side
MOSFET and low-side MOSFET.
2) Bypass ceramic capacitors are suggested to be put close to the Vin pin.
3) Ensure all feedback connections are short and direct. Place the feedback resistors and compensation
components as close to the chip as possible.
4) Rout SW away from sensitive analog areas such as FB.
5) Connect IN, SW, and especially GND respectively to a large copper area to cool the chip to improve
thermal performance and long-term reliability.
VER 1.3
7
ACE721E
1A, 1.5MHz Step-Down Converter
Packing Information
SOT-23-5
VER 1.3
8
ACE721E
1A, 1.5MHz Step-Down Converter
Packing Information
DFN2x2-6L
VER 1.3
9
ACE721E
1A, 1.5MHz 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 1.3
10