The ACE705 series are CMOS-based PFM step-up DC-DC Controller with low supply current and high
output voltage accuracy
ACE705
Technology High efficiency, Low supply current, step-up
DC/DC Controller
Description
The ACE705 series are CMOS-based PFM step-up DC-DC Controller with low supply current and high
output voltage accuracy. Quiescent current drawn from power source is as low as 6uA. It is capable
of
delivering 500mA output current at 4.0V output with 2V input Voltage. Only four external components
are
necessary: An inductor, a Schottky diode, an output filter capacitor and a NMOSFET or a NPN
transistor
All of these features make ACE705 series be suitable for the portable devices, which are supplied
by a
single battery to four-cell batteries.
ACE705 has a drive pin (EXT) for external transistor. So it is possible to load a large output
current with
a power transistor which has a low saturation voltage.
ACE705 integrates stable reference circuits and trimming technology, so it can afford high
precision and
low temperature-drift coefficient of the output voltage.
ACE705 is available in SOT-23-3 and SOT-23-5 packages which are PB free. And in
SOT-23-5 the
device can be switch on or off easily by CE pin, to minimize the standby supply current.
Features
• Deliver 500mA at 4.0V Output voltage with 2.0V input Voltage
• The converter output voltage can be adjusted from 2.5V～6.0V(In 0.1V step)
• Output voltage accuracy ±2％
• Low temperature-drift coefficient of the output voltage
±100ppm/℃
• Only four external components are necessary: An inductor, a Schottky diode an output
filter
capacitor and a NMOSFET or a NPN transistor
• High power conversion efficiency 90％
• Low quiescent current drawn from power source
6uA
Application
• Power source for PDA. DSC. MP3 Player. electronic toy and wireless mouse
• Power source for a single or dual-cell battery-powered equipments
• Power source for LED
Absolute Maximum Ratings
Parameter Symbol Max Unit
Input voltage range -0.3~12 V
Input voltage V(EXT) -0.3~Vout+0.3 V
CE pin voltage -0.3~Vout+0.3 V
EXT pin output current 0.7 A
Maximum power dissipation, Pd T=25℃
SOT-23-5
SOT-23-3
Maximum junction temperature
Operating free-air temperature range
Storage temperature range
0.25 W
0.15
150 ℃
-20~80 ℃
-40~125 ℃
VER 1.2 1
Packaging Type
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
SOT-23-3 SOT-23-5
3 5 4
1 2 1 2 3
Pin
VSS(GND)
VOUT
Ext
NC
CE
SOT-23-3
1
2
3
SOT-23-5
4
2
5
3
1
Function
Ground pin
Output pin, power supply for internal circuits
Switching pin
Chip enable pin (active high)
Ordering information
Selection Guide
ACE705 X XX XX + H
Halogen - free
Pb - free
BN : SOT-23-5
BM : SOT-23-3
Output Voltage :
2.5V / 3.0V V
Function Description :
1 : Without Enable circuit
2 : With Enable circuit
VER 1.2 2
Block Diagram
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
ACE705
Recommended Work Conditions
Item Min Nom Max Unit
Input voltage range 0.8 Vout V
Inductor 10 27 100 μH
Input capacitor 0 ≧10 μF
Output capacitor 47 100 220 μF
Vout pin filter capacitor 1 nF
Operating junction temperature -20 85 OC
*Suggestion: Use tantalum type capacitor to reduce the ripple of the output voltage. Use 1nF filter
ceramic type
capacitor to connect Vout pin and GND pin. The filter capacitor is recommended as close as possible
to Vout pin
and GND pin.
Electrical Characteristics
Default condition (unless otherwise provided): Vin=0.6xVout, Iout=10mA.Temperature=25℃. Use external
circuit in test circuit list.
Parameter Symbol Test Conditions Min Typ
Max Unit
2.45 2.5 2.55
2.646 2.7 2.754
2.94 3.0 3.06
Output Voltage
Input Voltage
Vout
Vin
3.234
3.528
3.92
4.9
5.88
3.3
3.6
4.0
5.0
6.0
3.366 V
3.672
4.08
5.1
6.12
12 V
VER 1.2 3
Input Current * (no
load)
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
Lin Iout=0mA, Vin=Vout*0.6 20 25 uA
Quiescent current *
Chip leakage current
IDD
Istandby
No external component,
Vout=Voutx1.05
VCE=0V
6 8 uA
1 uA
CE “H: threshold
voltage
CE “L” threshold
voltage
VCEH
VCEL
VCE
VCE
:0🡪2V
:2🡪0V
0.6
0.9
0.3
V
0.6 V
Oscillator frequency
FOSC
Vout=Vout*0.96 Test EXT pin
frequency
300
350
400
Khz
CE ”H”
CE “L”
EXT “H” output current
EXT “H” output current
Oscillator duty cycle
Efficiency
ICEH
ICEL
IEXTH
IEXTL
Duty
η
Vout=VCE=6V
Vout=VCE=6V
3.0V<=Vout<=3.9V
4.0V<=Vout<=4.9V
5.0V<=Vout<=6.9V
3.0V<=Vout<=3.9V
4.0V<=Vout<=4.9V
5.0V<=Vout<=6.9V
On(Vlx “L”) side
-0.5
-0.5
70
0
0
-21
-35
-41
23
25
31
75
90
0.5 uA
0.5 uA
mA
mA
80 %
%
Note :
1. Diode: Schottky type, such as: 1N5817, 1N5819, 1N5822
2. Inductor: 27uH(R<0.5Ω)
3. Output Capacitor: 100uF (Tantalum type)
4. Vout pin filter capacitor: 1nF (Ceramic type)
5. Input capacitor: 47uF
Typical Application
(1) Application with external NMOSFET
Vin D 1N5817
Vout
L 27uH
EXT OUT
Cin ACE705
47uF
Cout Rload
CE GND Cp 100uF Tan
OFF ON 1nF
Fig2
VER 1.2 4
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
(2) Application with external NPN transistor
ACE705
Fig3
Note: R₁=330Ω, C₁=10nF. (R₁ can be calculated by load. If load is light R₁’s value can be added. If
load is heavy R₁’s value can
be smaller. )
Detailed Description
The ACE705 series are boost structure, voltage-type pulse-frequency modulation(PFM) step-up DC-DC
controller. Only four external components are necessary: an inductor, a schottky diode, an output
filter
capacitor and a NMOSFET or a NPN transistor. The step-up DC-DC converter, constructed by ACE705,
can be adjusted from 2.5V to 6.0V, 0.1V step. By using the depletion technics, the
quiescent current
drawn from power source is lower than 8uA. The high efficiency device consists of resistors for
output
voltage detection and trimming, a start-up voltage circuit, an oscillator, a reference circuit, a
PFM control
circuit, a switch protection circuit and a driver transistor.
ACE705 integrates PFM control system. This system controls fixed power switch on duty
cycle
frequency to stabilize output voltage by calculating results of other blocks which
sense input voltage,
output voltage, output current and load conditions. In PFM modulation system, the frequency and
pulse
width is fixed. The duty cycle is adjusted by skipping pulses, so that switch on-time is changed
based on
the conditions such as input voltage, output current and load. The oscillate block inside ACE705
provides
fixed frequency and pulse width wave.
The reference circuit provides stable reference voltage to output stable output voltage. Because
internal
trimming technology is used, the chip output change less than ±2%. At the same time，the problem of
temperature-drift coefficient of output voltage is considered in design, so temperature-drift
coefficient of
output voltage is less than 100ppm/℃。
High-gain differential error amplifier guarantees stable output voltage at difference input voltage
and load. In order to reduce ripple and noise, the error amplifier is designed with high band-with.
ACE705 has a drive pin (EXT) for external transistor. So it is possible to load a large output
current with
a power transistor and a low saturation voltage. At very light load condition, the
switch current and
quiescent current of chip will effect efficiency certainly. So in very light load condition, the
efficiency will
drop. Therefore, it is recommended that user use ACE705 in the condition of load current as large as
several tens of mA to several hundreds of mA
VER 1.2 5
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
Selection of the External Components
Thus it can be seen, the inductor, schottky diode and external NMOSFET or NPN transistor.
affect the conversion efficiency greatly. The inductor and the capacitor also have great influence
on the output voltage ripple of the converter. So it is necessary to choose a suitable inductor, a
capacitor, an external NMOSFET or NPN transistor and a right schottky diode, to obtain high
efficiency and low ripple.
Before discussion，we define D≣Vout-Vin / Vout
(1)Inductor Selection
Above all, we should define the minimum value of the inductor that can ensure the boost DC-DC to
operate in the continuous current-mode condition.
Lmin≧D(1-D)²RL / 2f
The above expression is got under conditions of continuous current mode, neglect
Schottky diode’s
voltage, ESR of both inductor and capacitor. The actual value is greater that it. If inductor’s
value is less
than Lmin，the efficiency of DC-DC converter will drop greatly, and the DC-DC circuit will not be
stable.
Secondly, consider the ripple of the output voltage,
ΔI=D‧Vin / Lf
Im ax=Vin / (1-D)²RL + DVin / 2Lf
If inductor value is too small, the current ripple through it will be great. Then the current
through diode
and power switch will be great. Because the power switch on chip is not ideal switch, the energy of
switch
will improve. The efficiency will fall.
Thirdly，in general, smaller inductor values supply more output current while larger values start up
with
lower input voltage and acquire high efficiency.
An inductor value of 3uH to 1mH works well in most applications. If DC-DC converter delivers large
output current (for example: output current is great than 50mA), large inductor value is
recommended in
order to improve efficiency. If DC-DC must output very large current at low input supply voltage,
small
inductor value is recommended.
The ESR of inductor will effect efficiency greatly. Suppose ESR value of inductor is
rL，Rlₒₐd is load
resistor，then the energy can be calculated by following expression:
Δη≈ RL / Rlₒₐd (1-D)²
For example: input 1.5V, output is 3.0V, Rlₒₐd=20Ω, rL=0.5Ω, The energy loss is 10%.
Consider all above，inductor value of 47uH、ESR<0.5Ω is recommended in most applications. Large
value is recommended in high efficiency applications and smaller value is recommended
VER 1.2 6
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
(2)Output Capacitor Selection
Ignore ESR of capacitor，the ripple of output voltage is:
R=ΔVout / Vout=D / Rlₒₐd Cf
So large value capacitor is needed to reduce ripple. But too large capacitor value will slow down
system
reaction and cost will improve. So 100uF capacitor is recommended. Larger capacitor value will be
used
in large output current system. If output current is small (<10mA), small value is needed.
Consider ESR of capacitor，ripple will increase：
r'=r+Imax‧RESR / Vout
When current is large, ripple caused by ESR will be main factor. It may be greater than 100mV。The
ESR
will affects efficiency and increase energy loss. So low-ESR capacitor (for example: tantalum
capacitor) is
recommend or connect two or more filter capacitors in parallel.
(3)Diode Selection
Rectifier diode will affects efficiency greatly，Though a common diode (such as 1N4148) will work
well for
light load，it will reduce about 5%~10% efficiency for heavy load，For optimum performance, a Schottky
diode (such as 1N5817、1N5819、1N5822) is recommended.
(4)Input Capacitor
If supply voltage is stable, the DC-DC circuit can output low ripple, low noise and stable voltage
without
input capacitor. If voltage source is far away from DC-DC circuit, input capacitor value greater
than 10uF
is recommended.
(5)Vout~GND filter Capacitor
Because the chip’s switch current flows from Vout pin, then through the chip into GND pin.
Therefore if
the output capacitor’s two pins were not very near the chip’s Vout pin and GND pin, Vout ‘s stable
would
be affected. User will found that the output voltage will drop when load grows up if the output
capacitor’s
two pin is not very near the chip’s Vout pin and GND pin. In this condition, 1nF
ceramic capacitor is
recommended at very near the chip’s Vout pin and GND pin. So in all ACE705 application, two
capacitors
are needed to obtain stable output voltage. The 100μF tantalum output capacitor is
recommended to
stable output voltage nearby load. The 1nF Vout pin to GND pin ceramic filter capacitor is
recommended
to stable chip’s sense voltage.
VER 1.2 7
Test Circuits
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
(1) Output voltage test circuit
ACE705
Fig4
(2) Quiescent current test circuit
ACE705
Fig5
(3) Input Current (no load) test circuit
ACE705
Fig6
(4) Oscillator frequency and duty cycle test circuit
ACE705
Fig7
VER 1.2 8
Extend Applications
(1) 12V step-up application
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
ACE705
Fig8
Note: ACE705’s output voltage is 6V. When the output current is small or no load, the output
voltage will be unstable, use the
RZD for flowing the bias current through the zener diode. For step-up application, a diode(for
example: 1N4148) is
needed as starter circuit.
(2) Step-down application
ACE705
Fig9
Note: In step-down application, use starter circuit as above. 2.5V≤Vzener≤Vout. RST is needed for
bias current of zener
diode. This starter circuit also can be used in high voltage step-up application.
VER 1.2 9
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
(3) Flyback step-up/step-down application
ACE705
Fig10
Note: In step-down and step-up/step-down application, starter circuit in fig 8 is need. In step-up
application, simpler starter
circuit in fig 9 can be used.
Typical Characteristic
(Recommended operating conditions: L=10uH, Cin=47uF, Cout=100uF, Topt=25℃, unless otherwise noted)
1.Output Voltage VS. Output Current 2.Output Voltage VS. Output Current
ACE705230BN+ Output Voltage VS. Output Current ACE705240BN+ Output Voltage VS.
Output Current
Iout (mA)
Iout (mA)
3.Output Voltage VS. Output Current 4.Efficiency VS. Output Current
ACE705260BN+ Output Voltage VS. Output Current ACE705230BN+ Efficiency VS.
Output Current
Iout (mA)
Iout (mA)
VER 1.2 10
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
5. Efficiency VS. Output Current 6.Efficiency VS. Output Current
ACE705240BN+ Efficiency VS. Output Current ACE705260BN+ Efficiency VS.
Output Current
Iout (mA)
Iout (mA)
7. Ripple VS. Output Current 8.Ripple VS. Output Current
ACE705230BN+ Ripple VS. Output Current ACE705240BN+ Ripple VS. Output Current
Iout (mA)
Iout (mA)
9. Ripple VS. Output Current
ACE705260BN+ Ripple VS. Output Current
Iout (mA)
VER 1.2 11
Packing Information
SOT-23-3
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
VER 1.2 12
Packing Information
SOT-23-5
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
VER 1.2 13
ACE705
Technology High efficiency, multi-funtion step-up
DC/DC Controller
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 14