AT1308 [ETC]
Preliminary Product Information Micro-Power Step up DC-DC Converter; 初步产品信息微功率升压升压DC -DC转换器
| 型号： | AT1308 |
| 厂家： | 
ETC |
| 描述： | Preliminary Product Information Micro-Power Step up DC-DC Converter |
| 文件： | 总15页 (文件大小：377K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
Feature
Description
The AT1308 step-up converter is designed for
small or medium size LCD panel of high bias
voltage with a constant current to provide PDAs,
and other hand-held devices. It features a fast 1.0
MHz current-mode PWM control with a built-in
0.3Ω N-MOS that allows for smaller capacitor and
inductor. Fault condition protection uses cycle-by-
cycle current limiting to sense maximum inductor
current and thermal protection. Also included
soft-start circuitry eliminates inrush current during
start-up. The AT1308 is available in 5-pin SOT-25
packages.
•Operating Voltage:2.5V~6.0V
•High Operating Frequency: 1MHz
•Built-in N-MOS, Rds(on)≒ 0.3Ω (TYP)
•High Output Voltage: Up to 28V
•Shutdown Current <1µA
•Built-in Cycle-by-Cycle Current-limited.
•Built-in Soft-Start Function.
•1.5% 1.23V Reference.
•Tiny SOT-25 Package
Application
• STN/OLED Bias
• Personal Digital Assistants (PDAs)
• DSC
Block Diagram
VIN
LX
ON/OFF
Thermal
Soft-Start
EN
FB
Control
Logic
Protection
VBG
1.23V
VBG
N
+
-
Control Logic
Current Limit
400mA
+
-
GND
Aimtron reserves the right without notice to change this circuitry and specifications.
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
1
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
Pin Configuration
SOT-25
(TOP VIEW)
LX
GND
FB
1
2
3
5
4
VIN
EN
Ordering Information
Part number
AT1308X
AT1308X_GRE
Package
SOT-25
SOT-25,Green
Marking
Date Code
,Date Code with one bottom line
Pin Description
Pin N0. Symbol I / O Description
1
2
LX
I
Step-up Regulator N-MOS Drain. Place output diode and inductor.
Ground
GND
P
Step-Up Regulator Feedback Input. Connect a resistive divider from
output to FB to analog ground.
3
FB
I
Enable Control Input. Pull EN low to force the controller into shutdown.
If unused , connect EN to Vin for normal operation.
Power supply.
4
5
EN
I
VIN
P
Absolute Maximum Ratings[note1]
Parameter
Rated Value
-0.3 to +6.5
-0.3 to +30
-0.3 to +6.5
0.8
Unit
V
VIN voltage
LX voltage
V
EN , FB to GND
V
A
W
℃
℃
℃
Switch Current (ILX)
Continuous power dissipation (SOT-25 Ta=+25OC)
Operating Junction Temperature Range
Lead Temperature (Soldering 5 sec)
Storage Temperature
0.25
-30 to 85
260
-65 to 125
250
2
200
Package Thermal Resistance (ΘJA)
ESD Susceptibility (HBM)
ESD Susceptibility (MM)
Note1:Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability
℃/W
KV
V
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
2
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
Recommended Operation Conditions
Parameter
Symbol
Values
Unit
Min.
2.5
-20
Typ.
―
Max.
6.0
Power supply voltage
Operating temperature
VIN
Top
V
℃
+25
+85
Electrical Characteristics
(VIN=2.5V, Ta=+25℃, unless otherwise noted)
Parameter
Symbol
Test Condition
VIN input Voltage
Min. Typ. Max. Units
Operating V IN Range
VIN
2.5
-
2.2
6.0
-
V
Under Voltage Thershold
Switch- Off Input Current
Shutdown Current
UVLO VIN falling, 100mV hysteresis
-
-
-
V
uA
uA
V
IIN1
IIN3
VFB
IFB
No Switching
EN=0V
100 120
-
1
Feedback Reference
1.212 1.23 1.248
FB Input Bais Current
VFB =1.23V
2.5V< VIN <6.0V
-
-
-
1
-
uA
Output Voltage Line Regulation
0.1
%
Switching Frequency
Maximum Duty
fOSC
DMAX
tSS
-
-
1
-
-
MHz
%
90
Soft-Start charging time
Switching Current Limit
0.5
400
ms
mA
Ω
I
VIN=3.0V,duty cycle=80%
-
-
LX
I
=350mA
LX ON Resistance
LX Leakage Current
EN Input Current
RLX
ILeakage
IEN
-
0.3
-
LX
VLX =29V, EN=0V
-
-
1
uA
uA
V
EN=5V
-
-
-
8
VIH
VIL
0.1V hysteresis
2.0
-
-
EN Input Level
-
0.8
V
Thermal Shutdown
120
℃
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
3
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
Application Circuit
10uH
L1
MBR140WS
10pF
1uF
3.3V/
VIN
50mA
2.5V to 4.2V
4u7F/
6V3
VIN
LX
10uH
L2
10uF/
6V3
500K
R1
AT1308
EN
FB
297K
R2
※
L1, L2 : SR0302 (0.25Ohm/0.8A)
GND
※
VOUT=VREFX (1+R1/R2)
Fig1. 1-Cell Li-Ion to 3.3V SEPIC Converter
10uH
L1
MBR140WS
1uF
5V/
VIN
40mA
3.0V to 6.0V
4u7F/
6V3
VIN
LX
10uH
L2
10pF
R1
10uF/
6V3
AT1308
500K
163K
FB
EN
R2
※
※
L1, L2 :SR0302 (0.25Ohm/0.8A)
VOUT=VREFX (1+R1/R2)
GND
Fig2. 4-Cell to 5V SEPIC Converter
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
4
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
-15V/
4mA
4.7uF/
16V
0.1uF
0.1uF
BAT54S
10uH
L1
15V/
4mA
VIN
2.5V to 5.0V
4u7F/
6V3
BAT54S
VIN
LX
10pF
4.7uF/
16V
AT1308
500K
FB
EN
44K
※L1 :SR0302 (0.25Ohm/0.8A)
GND
Fig3. ±15V Dual Output Converter with Output Disconnect
10uH
L1
15V/
20mA
VIN
2.5V to 5.0V
MBR140WS
4.7uF/
6V3
VIN
LX
10uF/
16V
10pF
AT1308
500K
R1
FB
EN
44K
R2
※
L1 :SR0302 (0.25Ohm/0.8A)
VOUT=VREFX (1+R1/R2)
GND
※
Fig4. 15V Boost Converter
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
5
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
VOUT3
VOUT2
10K
510
-13V_TFT
17V_TFT
BAT54S
open
BAT54S
0.1uF
0.1uF
1uF/25V
1uF/25V
10uF/25V
Zener
13V
Zener
17V
open
1uF
1uF
0.1uF
4.7uH
0.1uF
BAT54S
BAT54S
VOUT1
7.5V_TFT
VIN
5V
MBR140S
10uF/10V
VIN
LX
10pF
1uF
SW
AT1308
500K
FB
EN
98K
GND
Fig5. TFT_ Power solution
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
6
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
Typical Characteristics
EFFICIENCY vs OUTPUT CURRENT
90
85
80
75
70
65
60
55
50
45
40
Vo=15V
L=10uH
2.5V
3.6V
5.0V
1 3 5 8 10 13 15 18 20
Io-Output Current-mA
EFFICIENCY vs LOAD CURRENT
90
Vo=15V
85
80
75
70
65
60
55
50
Vin=3.3V
6.8uH
10uH
22uH
1 3 5 7 10 13 15 18 20
Io-Load Current-mA
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
7
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
EFFICIENCY vs INPUT VOLTAGE
90
85
80
75
70
Vo=15V
L=10uH
5mA
10mA
20mA
2.5 3 3.3 3.6 3.9 4.2 4.5 5 5.5
Vin-Input Voltage-V
CURRENT LIMIT vs SUPPLY VOLTAGE
700
650
600
550
500
450
400
350
300
Vo=15V
L=10uH
L=22uH
2.5
3
3.5
4
4.5
5
5.5
6
VIN-SUPPLY VOLTAGE (V)
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
8
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
QUIESCENT CURRENT vs INPUT VOLTAGE
500
450
400
350
300
250
200
150
100
50
Vo=15V
L=10uH
TA=25OC
0
2.5 2.8 3 3.3 3.6 4 4.2 4.5 5 5.5 6
VIN-INPUT VOLTAGE (V)
SW ITCHING FREQUENCY vs TEMPERATURE
975
970
965
960
955
950
945
940
VIN=2.5V
Vo=15V
L=10uH
-20 -10
0
10
25
40
55
85
TEMPERATURE (oC)
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
9
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
Load Transient Response
VIN=2.5V, Vout=15V, L=10uH, Iout=5mA to 25mA
Ch1:Vout (AC mode), Ch4:Iout, Time:0.5ms/div
Line Transient Response
VIN=2.5V to 6.0V, Vout=15V, L=10uH, Iout=20mA
Ch1:VIN, Ch2:Vout (AC mode), Ch4:IIN, Time:0.5s/div
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
10
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
Start up Waveform with Load
VIN=2.5V, Vout=15V, L=10uH, Iout=20mA
Ch1:Vout, Ch2:EN, Ch4:IIN, Time:1.0ms/div
LX Switching Waveform
VIN=3.3V, Vout=20V, L=10uH
Ch1:LX, Ch4:ILX, Time:0.5us/div
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
11
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
Function Description
The AT1308 is designed primarily for use in STN/OLED bias applications. The output voltage of the
step-up converter can be set from Vin to 26V with external resistive voltage divider. The boost
converter operates in current-mode PWM and a constant frequency of 1.0 MHz. Depending on duty
cycle of each switching cycle can regulate output voltage. On the rising edge of the internal clock, the
control and driver logic block sets internal flip-flop when the output voltage is too low, which turns on
the N-MOS . The external inductor current ramps up linearly, storing energy in a magnetic filed. Once
peak current of inductor over trans-conductance output level , the N-MOS turns off, the flip-flop resets,
and external schottky diode turns on . This forces the current through the inductor to ramp back down,
transferring the energy stored in the magnetic field to the output capacitor and load. To reduce external
component amount, the device will be built-in internal loop compensation.
Enable Control
Digital logic of EN provides an electrical ON/OFF control of the power supply. Connecting this pin to
ground or to any voltage less than 0.7V will completely turn off the regulator. In this state, current
drain from the input supply is less than 1uA , the internal reference, error amplifier, comparators, and
biasing circuitry turn off .
EN works as a simple on/off control. Drive EN high to enable the device, or drive EN low for
shutdown.
Soft-Start
Soft-start allows a gradual increase of the internal current-limit level for the step-up converter during
power-up to reduce input surge currents. As the internal current source charges the internal soft-start
capacitor, the peak N-MOS current is limited by the voltage on the capacitor.
Cycle-by-Cycle Over-Current Protection
The AT1308 provides cycle-by-cycle over-current protection. Current limit is accomplished using a separate
dedicated comparator. The cycle-by-cycle current limit abbreviates the on-time of the N-MOS in event that
the current of flowing N-MOS is greater than the current limit value. The current-limit feature protection
against a hard short or over-current fault at the output.
Thermal-Overload Protection
Thermal-overload protection limits total power dissipation in the AT1308. When the junction
temperature exceeds Tj=130 ℃, a thermal sensor activates the thermal protection, which shuts down
the IC, allowing the IC to cool. Once the device cools down by 10 ℃, IC will automatically recover
normal operation. For continuous operation
,
do not exceed the absolute maximum
junction-temperature rating of Tj=120 ℃.
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
12
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
Power dissipation consideration
The AT1308 maximum power dissipation depends on the thermal resistance of the IC package and
circuit board, the temperature difference between the die junction and ambient air, and the rate of any
airflow. The power dissipation in the device depends on the operating conditions of the regulator.
The step-up converter dissipates power across the internal N-MOS as the controller ramps up the
inductor current. In continuous condition, the power dissipated internally can be approximated by :
IO ×V
Vin
Vin × D
12 fOSC × L
1
P
= [(
O )2 +
(
)2 ]× RDS(ON ) × D
boost
where
IO : It is the load current.
OSC : It is a switching frequency.
f
Applications Information
External components of boost converter can be designed by performing simple calculations. It need to
follow regulation by the output voltage and the maximum load current, as well as maximum and
minimum input voltages. Begin by selecting an inductor value. Once L is know, choose the diode and
capacitors.
Boost inductor
Inductor selection depends on input voltage, output voltage, maximum current , switching frequency
and availability of inductor values. The following boost circuit equations are useful in choosing the
inductor values based on the application. They allow the trading of peak current and inductor value
while allowing for consideration of component availability and cost.
The peak inductor current is given by:
∆IL
2
ILpeak = ILAVG
+
IO
ILAVG
=
1− D
where:
△IL is the inductor peak-to-peak current ripple and is decided by:
Vin
L
D
fOSC
∆IL =
×
D is the MOSFET turn on ratio and is decided by:
VO −V in
D =
VO
fOSC is the switching frequency.
The inductor should be chosen to be able to handle this current and inductor saturation current rating
should be greater than IPEAK
.
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
13
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
Diode selection
The output diode has average current of IO, and peak current the same as the inductor’s peak current
and a voltage rating at least 1.5 times the output voltage. Schottky diode is recommended and it should
be able to handle those current.
Output Capacitor
The AT1308 is specially compensated to be stable with capacitors, which have a worst- case minimum
value of 1uF at the particular VOUT being set. Output ripple voltage requirements also determine the
minimum value and type of capacitors. Output ripple voltage consists of two components the voltage
drop caused by the switching current through the ESR of the output capacitor and the charging and
discharging of the output capacitor:
VO −Vin
IO
VRIPPLE = ILPEAK × ESR +
×
VO
COUT × fOSC
For low ESR ceramic capacitors, the output ripple is dominated by the charging or discharging of the
output capacitor.
Impacting frequency stability of the overall control loop, Ceramic capacitors are preferred on the
output capacitance, but tantalum capacitor may also suffice., If it use tantalum capacitor on the output
terminal, that in addition the capacitance parallel with feedback resistor network is necessary. These
frequency response effects together with the internal frequency compensation circuitry of AT308
modify the gain and phase shift of the closed loop system.
PCB layout guidelines
Careful printed circuit layout is extremely important to avoid causing parasitical capacitance and line
inductance. The following layout guidelines are recommended to achieve optimum performance.
• Please the boost converter diode and inductor close to the LX pin and no via. Keep traces short,
direct, and wide.
• Please ceramic bypass capacitors near the input/output pin.
• Locate all feedback sense resistor as close to the feedback pins as possible.
• The ground connections of VIN and VOUT should be as close together as possible.
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
14
AT1308
Preliminary Product Information
Micro-Power Step up DC-DC Converter
Small Outline SOT-25
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
Rev A ; 01/18/05
15
相关型号：
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