ACE701
Technology
PFM STEP-UP DC/DC Converter with High Efficiency and Low Noise
Description
The ACE701 series are CMOS-based PFM step-up DC-DC Converter. The converter can start up by
supply voltage as low as 0.8V, and capable of delivering maximum 200mA output current at 3.3V output
with 1.8V input Voltage. Quiescent current drawn from power source is as low as 5.5uA. All of these
features make ACE701 series be suitable for the portable devices, which are supplied by a single battery
to four-cell batteries.
To reduce the noise caused by the switch regulator, ACE701 is well considerated in circuit design and
manufacture. So that the interferer to other circuits by the device is reduced greatly.
ACE701 integrates stable reference circuits and trimming technology, so it can afford high precision and
low temperature-drift coefficient of the output voltage.
ACE701 is available in SOT-89-3、SOT-23-3、SOT-89-5 and SOT-23-5 packages which is PB free. And
in 5-pin packages, such as SOT-23-5 and SOT-89-5, the device can be switch on or off easily by CE pin,
to minimize the standby supply current.
Features
•
•
•
•
•
•
•
•
•
•
•
Deliver 200mA at 3.3V Output voltage with 1.8V input Voltage
Low start-up voltage (when the output current is 1mA)--------------------------0.8V
The converter output voltage can be adjusted from 2.5V½6.0V(In 0.1V step)
Output voltage accuracy -----------±2％
Low temperature-drift coefficient of the output voltage------------------±100ppm/℃
Only three external components are necessary: An inductor, a Schottky diode and an output filter
capacitor
High power conversion efficiency---85％
Low quiescent current drawn from power source------------------------------------- <5.5uA
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
Input supply voltage
Input voltage
CE pin voltage
Lx pin output current
Power Dissipation
SOT-89-3
SOT-23-5
SOT-23-3
Junction temperature
Storage temperature
Operating free-air temperature
Symbol
V
IN
V
I(LX)
Max
Unit
-0.3~12
V
-0.3~Vout+0.3 V
-0.3~Vout+0.3
0.7
A
0.5
0.15
0.15
150
- 40 to 125
-20 ~ 80
W
O
O
T
J
T
S
C
C
O
C
VER 1.2
1
Technology
PFM STEP-UP DC/DC Converter with High Efficiency and Low Noise
Packaging Type
SOT-89-3
SOT-23-3
3
ACE701
SOT-23-5
5
4
SOT-89-5
5
4
1
2
3
1
2
1
2
3
1
2
3
Pin
SOT-89-3 SOT-23-3 SOT-23-5 SOT-89-5
V
SS
(GND)
1
1
4
4
V
OUT
L
X
(Ext)
NC
CE
2
3
2
3
2
5
3
1
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
ACE701 X XX XX + H
Halogen - free
Pb - free
BN : SOT-23-5
BM : SOT-23-3
AM : SOT-89-3
AN : SOT-89-5
Output Voltage :
2.5V / 3.0V ….. 6.0V
Function Description :
1 : Internal Tr. Driver, Without Enable circuit
2 : Internal Tr. Driver, With Enable circuit
3 : External Tr. Driver, Without Enable circuit
4 : External Tr. Driver, With Enable circui
VER 1.2
2
Technology
PFM STEP-UP DC/DC Converter with High Efficiency and Low Noise
Block Diagram
ACE701
ACE701
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
Operating junction temperature -20
85
℃
*Suggestion: Use tantalum capacitor to reduce the ripple of the output voltage.
Electrical Characteristics
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
3.234 3.3 3.366
V
3.528 3.6 3.672
3.92 4.0 4.08
4.9
5.0
5.1
5.88 6.0 6.12
12
V
12
15
uA
0.8
0.9
V
0.6
0.7
V
4
0.4
7
0.5
VER 1.2
Output Voltage
Vout
Input Voltage
Input Current
Start-up voltage
Hold-on voltage
Quiescent current drawn from
power source
Switch ON Resistance
Vin
Lin
Vstart
Vhold
I
DD
Rswon
Iout=0mA, Vin=Vout*0.6
Iout=1mA, Vin:0 2V
Iout=1mA, Vin:2 0V
Without external components,
Vout=Vout x 1.05
uA
Ω
3
Technology
PFM STEP-UP DC/DC Converter with High Efficiency and Low Noise
LX leakage current
CE “H” threshold voltage
CE “L” threshold voltage
Oscillator frequency
Oscillator duty cycle
Efficiency
Note :
1.
2.
3.
Diode: Schottky type, such as: 1N5817, 1N5819, 1N5822
Inductor: 27uH(R<0.5Ω)
Capacitor: 100uF (Tantalum type)
ACE701
1.0
I
LXleak
V
CEH
V
CEL
F
OSC
Maxdty
η
Vout=Vlx=6V
V
CE
: 0 2V
V
CE
: 2 0V
LX on “L” side Vout=Vout * 0.96
On (Vlx “L”) side
0.6
300
70
0.9
0.3
350
75
85
0.6
400
80
uA
V
V
Khz
%
%
Typical Application Circuit
D 1N5819
Vin
L 27uH
LX
LX OUT
ACE701
GND
Iout
Cout
100uF
Rload
Tan
Vout
Cin 47uF
Detailed Description
The ACE701 series are boost structure, voltage-type pulse-frequency modulation(PFM) step-up DC-DC
converter. Only three external components are necessary: an inductor, an output filter capacitor and a
schottky diode. And the converter’s low noise and low ripple output voltage can be adjusted from 2.5V to
5.0V, 0.1V step. By using the depletion technics, the quiescent current drawn from power source is lower
than 7uA. 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.
The PFM control circuit is the core of the ACE701 IC. This block controls power switch on duty cycle 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 ACE701 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/℃。
VER 1.2
4
Technology
PFM STEP-UP DC/DC Converter with High Efficiency and Low Noise
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.
Though at very low load condition, the quiescent current of chip do effect efficiency certainly. The four
main energy loss of Boost structure DC-DC converter in full load are the ESR of inductor, the voltage of
Schottky diode, on resistor of internal N-channel MOSFET and its driver. In order to improve the efficiency,
ACE701 integrates low on-resistor N-channel MOSFET and well design driver circuits. The switch energy
loss is limited at very low level.
ACE701
Selection of the External Components
Thus it can be seen, the inductor and schottky diode 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 and a right schottky diode, to obtain high efficiency,
low ripple and low noise.
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)
2
R
L
/ 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)
2
R
L
+ 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 r
L
，R
load
is load
resistor，then the energy can be calculated by following expression:
Δη≈
R
L
/ R
load
(1-D)
2
VER 1.2
5
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