AMS AS1341 Datasheet
Annonce
Annonce
A S 1 3 4 1
6 5 0 m A , U l t r a l o w R i p p l e S t e p D o w n D C / D C C o n v e r t e r
1 General Description
The AS1341 is a high-efficiency step-down converter with adjustable output voltages from 1.25V to V
IN
using supply voltages of up to
20V.
An integrated current-limited 0.4
Ω
MOSFET delivers load currents up to 600mA.
The AS1341 also includes a 100% duty cycle LDO mode with a low dropout of only 250mV for high efficiency if input voltages is in the range of the output voltage.
The AS1341 has a low quiescent current (12µA) to improve lightload efficiency and minimize battery use, and draws only 0.8µA in shutdown mode.
High switching frequencies (up to 200kHz) allow the use of small surface-mount inductors and output capacitors.
The device is available in a TDFN-8 3x3mm pin package.
Figure 1. AS1341 - Typical Application
2 Key Features
Output Voltages: Fixed 5V or Adjustable
Input Voltage Range: 4.5V to 20V
Output Current: Up to 600mA
1.25V Lowest Output Voltage
Efficiency: up to 96%
Quiescent Supply Current: 12µA
Power-OK Output
Internal 0.4
Ω
P-Channel MOSFET
Shutdown Current: 0.8µA
100% Maximum Duty Cycle for Low Dropout
Current-Limited Architecture
Thermal Shutdown
TDFN-8 3x3mm Package
3 Applications
The device is ideal for notebook computers, distributed power systems, keep-alive supplies, and any other battery-operated, portable device.
V
IN
4.5V to 20V
C
IN
5
IN
7
SHDNN
6
ILIMIT
2
GND
AS1341
4
LX
D1
8
OUT
3
POK
1
FB
L1
C
OUT
+
V
OUT
= 5V
R
PULL
Indicates High-Power Trace www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
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AS1341
Datasheet - P i n A s s i g n m e n t s
4 Pin Assignments
Figure 2. Pin Assignments (Top View)
FB 1
GND 2
POK 3
LX 4
8 OUT
7 SHDNN
AS1341
6 ILIMIT
9
5 IN
4.1 Pin Descriptions
Table 1. Pin Descriptions
Pin Number Pin Name
1
2
FB
GND
3
4
5
6
POK
LX
IN
ILIMIT
7 SHDNN
8
9
OUT
NC
Description
Feedback Input
. For the fixed 5V output connect this pin to GND. For adjustable output, connect to a resistive divider between V
OUT
and GND to set the output voltage between 1.25V and V
IN
.
Ground
Power OK
. Active-low open-drain reset output.
Note:
Connect pin POK to GND when the Power-Ok feature is not used.
Inductor Connection
. Connect this pin to an external inductor.
4.5V to 20V Input Supply Voltage
Peak Current Control Input
. Connect this pin to IN or GND to set peak current limit
.
Shutdown Input
. A low on this pin puts the AS1341 into shutdown mode. Supply current is reduced to
0.8µA and LX goes high-impedance.
Regulated Output Voltage High-Impedance Sense Input
. For the fixed 5V output connect this pin to
V
OUT
. For adjustable output connect this pin to GND.
Exposed Pad.
This pad is not connected internally. Connect to GND or do not connect.
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AS1341
Datasheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
the device at these or any other conditions beyond those indicated in
Electrical Characteristics on page 4 is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
Table 2. Absolute Maximum Ratings
Parameter
Electrical Parameters
IN to GND
Min
-0.3
Max Units
V
Comments
LX to GND
FB to GND
ILIMIT, SHDNN, OUT, POK to GND
-2
-0.3
-0.3
+23
V
IN
+ 0.3
+5
V
IN
+ 0.3
2
V
V
V
A Peak Input Current
Temperature Ranges and Storage Conditions
Thermal Resistance
Θ
JA
Storage Temperature Range
Junction Temperature
-55
36.3
+150
+150
ºC/W
ºC
ºC on PCB
Package Body Temperature
+260 ºC
The reflow peak soldering temperature (body temperature) specified is in accordance with
IPC/
JEDEC J-STD-020 “Moisture/Reflow Sensitivity
Classification for Non-Hermetic Solid State Surface
Mount Devices”.
The lead finish for Pb-free leaded packages is matte tin
(100% Sn).
Humidity non-condensing
Moisture Sensitive Level
5
1
85 %
Represents a max. floor life time of unlimited www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
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AS1341
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
V
IN
= +12V, SHDNN = V
IN
, Typical values are at T
AMB
= +25ºC (unless otherwise specified). Specifications based on circuit shown in
.
Table 3. Electrical Characteristics
Symbol
T
AMB
V
IN
V
OUT
V
DROPOUT
V
FB
I
IN
I
INDROP
V
UVLO
Parameter
Operating Temperature Range
Input Voltage Range
Output Voltage (Preset Output)
Output Voltage (Adjustable)
Dropout Voltage
Line Regulation
Load Regulation
Feedback Set Voltage (Adjustable
Output)
Input Supply Current
Input Supply Current in Dropout
Input Shutdown Current
Input Undervoltage Lockout
Threshold
I
FB
OUT Bias Current
FB Bias Current
FB Threshold Low
Thermal Shutdown
DC-DC Switches
t
OFFMIN
LX Switch Minimum Off-Time t
ONMAX
LX Switch Maximum On-Time
R
LX
I
LXPEAK
LX Switch On-Resistance
LX Current Limit
LX Zero-Crossing Threshold
Zero-Crossing Timeout
LX Switch Leakage Current
Conditions
FB = GND
I
OUT
= 600mA, ILIMIT = V
IN
V
IN
= 6V to 20V, 200
Ω
load
ILIMIT = V
IN
, I
OUT
= 0 to 500mA
No load
No load
SHDNN = GND
V
IN
rising
V
IN
falling
V
OUT
= 5.5V
V
FB
= 1.3V
10ºC hysteresis
V
FB
= 1.3V
V
IN
= 6V
V
IN
= 4.5V
ILIMIT = GND, L = 39µH
ILIMIT = IN, L = 10µH
LX does not rise above the threshold
V
IN
= 20V, LX = GND, T
AMB
= +25ºC
V
IN
= 20V, LX = GND
Min
-45
4.5
4.85
1.25
1.212
3.6
3.5
2
-25
50
0.2
8
500
1000
-75
Typ
5.00
250
0.1
1
1.25
12
45
0.8
4.0
3.9
3.5
100
145
0.4
10
0.4
0.5
700
1400
30
Max
85
20
5.15
V
IN
1.288
0.6
12
900
1800
+75
4.3
5
+25
150
18
60
3
4.4
0.1
1
Units
°C
V
V mV
%/V
%
V
µA
µA
µA
V
µA nA mV
ºC
µs
µs
Ω mA mV
µs
µA
Control Inputs
Digital Input Level
Digital Input Leakage Current
SHDNN, ILIMIT = GND
SHDNN, ILIMIT = IN
V
SHDNN
, V
ILIMIT
= 0 to 20V, V
IN
= 20V
2.4
-100
0.8
+100
V nA
Power-OK
Power-OK Threshold
POK Output Voltage Low
POK Output Leakage Current
Falling edge, relative to V
OUT
I
POK
= 1mA
V
IN
, V
POK
= 16V, T
AMB
= 25°C
V
IN
, V
POK
= 16V
90 92.5
95
0.4
0.1
1
%
V
µA
Note:
All limits are guaranteed. The parameters with min and max values are guaranteed with production tests or SQC (Statistical Quality
Control) methods.
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AS1341
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
7 Typical Operating Characteristics
V
OUT
= 5V, T
AMB
= +25ºC (unless otherwise specified).
Figure 3. Efficiency vs. I
OUT
100
ILIMIT = high
95
90
85
80
75
70
65
60
55
50
0.1
1 10
V
IN
= 6V
V
IN
= 12V
V
IN
= 20V
100
Output Current (mA)
1000
Figure 5. Efficiency vs. I
OUT
; V
OUT
= 3.3V
100
ILIMIT = high
95
90
85
80
V
IN
= 4.5V
V
IN
= 20V
75
70
65
60
55
V
IN
= 12V
50
0.1
1 10 100
Output Current (mA)
1000
Figure 7. Efficiency vs. I
OUT
; V
IN
= 12V
95
ILIMIT = high
90
85
80
75
70
65
0.1
1 10 100
Output Current (mA)
22uH
10uH
4.1uH
1000 www.ams.com/DC-DC_Step-Up/AS1341
Figure 4. Efficiency vs. I
OUT
100
ILIMIT = low
95
90
85
80
75
70
65
60
55
50
0.1
1
V
IN
= 6V
10
V
IN
= 12V
V
IN
= 20V
100
Output Current (mA)
Figure 6. Efficiency vs. I
OUT
; V
OUT
= 3.3V
100
ILIMIT = low
95
V
IN
= 4.5V
90
V
IN
= 12V
85
80
V
IN
= 20V
75
70
65
60
55
50
0.1
1 10 100
Output Current (mA)
Figure 8. Efficiency vs. I
OUT
; V
IN
= 12V
95
ILIMIT = low
90
85
80
75
70
65
0.1
1 10 100
Output Current (mA)
1000
1000
10uH
39uH
22uH
1000
Revision 1.09
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AS1341
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
Figure 9. Efficiency vs. Input Voltage
100
95
90
85
80
75
70
5
VOUT=3.3V, IOUT=500mA
VOUT=5V, IOUT=500mA
VOUT=3.3V, IOUT=250mA
VOUT=5V, IOUT=250mA
8 11 14
Input Voltage (V)
17 20
Figure 10. Output Voltage vs. Input Voltage
5.15
5.1
5.05
5
4.95
4.9
4.85
5 8 11 14
Input Voltage (V)
17
IOUT = 1mA
IOUT = 100mA
IOUT = 300mA
IOUT = 500mA
IOUT = 600mA
20
Figure 11. Output Voltage vs. Input Voltage;
V
OUT
= 3.3V
3.4
3.35
3.3
3.25
IOUT = 1mA
IOUT = 100mA
IOUT = 300mA
IOUT = 500mA
Figure 12. Peak Switch Current vs. Input Voltage;
V
OUT
= 3.3V
1.8
1.6
1.4
1.2
1
0.8
ILIMIT = high
L=10µH
ILIMIT = high
L=39µH
ILIMIT = low
L=10µH
ILIMIT = low
L=39µH
0.6
0.4
0.2
0
5 8 11 14
Input Voltage (V)
17 20
3.2
4 6 8 10 12 14 16 18 20
Input Voltage (V)
Figure 13. Switching Frequency vs. Output Current;
V
IN
= 12V, V
OUT
= 5V, L = 10µH
250
ILIMIT = low
200
Figure 14. Switching Frequency vs. Output Current;
250
V
IN
= 12V, V
OUT
= 3.3V, L = 10µH
200
ILIMIT = low
150
150
100 100
ILIMIT = high
50
0
0 100 200 300 400 500 600
Output Current (mA) www.ams.com/DC-DC_Step-Up/AS1341
50
Revision 1.09
ILIMIT = high
0
0 100 200 300 400 500 600
Output Current (mA)
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AS1341
Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s
Figure 15. Load Regulation, V
OUT
vs. I
OUT
;
V
IN
= 12V, V
OUT
= 5V
5.15
5.1
5.05
5
4.95
4.9
ILIMIT = high
ILIMIT = low
4.85
0 100 200 300 400 500 600
Output Current (mA)
Figure 17. Line Transient Response; I
OUT
= 500mA
Figure 16. Load Regulation, V
OUT
vs. I
OUT
;
V
IN
= 12V, V
OUT
= 3.3V
3.4
3.35
3.3
ILIMIT = low
ILIMIT = low
3.25
3.2
0 100 200 300 400 500 600
Output Current (mA)
Figure 18. Load Transient Response
200µs/Div
Figure 19. LX Waveform; V
IN
= 20V, I
OUT
= 500mA
15V
10V
10µs/Div
Figure 20. Startup Waveform; R
LOAD
= 100
Ω
500mA
10mA
2µs/Div www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
100µs/Div
5V
0V
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AS1341
Datasheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
The AS1341 step-down converter was specifically designed for battery-powered portable devices, including laptop computers, PDAs, and MP3/
DVD/CD players. The advanced current-limited control scheme provides high-efficiency over a wide range of output loads. The highly-efficient operation (up to 100% duty cycle) allows extremely low dropout voltage, increasing the usable supply voltage range. In no-load conditions the
AS1341 draws only 12µA; in shutdown mode it draws only 0.8µA to further reduce power consumption and extend battery life.
The AS1341 features an integrated 20V switching MOSFET, internal current sensing, and a high switching frequency, for minimal PCB space and external component requirements.
Figure 21. AS1341 - Block Diagram - 5V fixed Output Voltage
5
IN
C
IN
7
SHDNN
6
ILIMIT
Current Limit
Control
+
–
+
–
AS1341
Q R
S
Maximum On-
Time Delay
Minimum Off-Time
Delay
–
+
3
POK
+
–
–
+
V
SET
1.25V
+
–
100mV
+
–
4
LX
8
OUT
1
FB
D1
2
GND
R
PULL
L1
C
OUT
+
8.1 Current-Limit Control
The AS1341 uses a proprietary current-limiting control scheme with operation up to 100% duty cycle. The DC-DC converter pulses as needed to maintain regulation, resulting in a variable switching frequency that increases with the load. This eliminates the high-supply currents associated with conventional constant-frequency pulse-width-modulation (PWM) controllers that unnecessarily switch the MOSFET.
When the output voltage is too low, the error comparator sets a flip-flop, which turns on the internal P-channel MOSFET and begins a switching cycle. The inductor current ramps up linearly, storing energy in a magnetic field while charging the output capacitor and servicing the load
The MOSFET turns off when the peak current limit is reached, or when the maximum on-time of 10µs is exceeded and the output voltage is in regulation. If the output is out of regulation and the peak current is never reached, the MOSFET remains on, allowing a duty cycle up to 100%.
This feature ensures the lowest possible dropout voltage.
, and the current through the inductor ramps back down, transferring the stored energy to the output capacitor and load. The MOSFET remains off until the 0.4µs minimum off-time expires, and the output voltage goes out of regulation.
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AS1341
Datasheet - D e t a i l e d D e s c r i p t i o n
8.2 Dropout Voltage
A buck converter’s minimum input-to-output voltage differential (dropout voltage) determines the lowest usable supply voltage. In batterypowered systems, this limits the useful end-of-life battery voltage. To maximize battery life, the AS1341 operates with duty cycles up to 100%, which minimizes the dropout voltage and eliminates switching losses while in dropout. When the supply voltage approaches the output voltage, the P-channel MOSFET remains on continuously to supply the load.
Note:
Dropout voltage is defined as the difference between the input and output voltages when the input is low enough for the output to drop out of regulation.
For a step-down converter with 100% duty cycle, dropout is related to the MOSFET drain-to-source on-resistance (R
DSON
) and inductor series resistance (R
INDUCTOR
), and thus it is proportional to the load current:
V
DROPOUT
= I
OUT
x (R
DSON
+ R
INDUCTOR
) (EQ 1)
8.3 Shutdown
A logic low on pin SHDNN shuts down the AS1341; a logic high on SHDNN powers on the device.
In shutdown mode the supply current drops to 0.8µA to maximize battery life, and the internal P-channel MOSFET turns off to isolate the output from the input. The output capacitance and load current determine the output voltage decay rate.
Note:
Pin SHDNN should not be left floating. If the shutdown feature is not used, connect SHDNN to IN.
8.4 Power-OK Output
The AS1341 provides a Power OK output (POK) that goes high-impedance when the output reaches 92.5% of its regulation point. POK goes low when the output is below 92.5% of the regulation point and the AS1341 is turned on (IN
≥
4.5V and SHDNN
≥
2.4V). A 12k
Ω
to 1M
Ω
pullup resistor between pin POK and pin IN or pin OUT or another voltage (
≤
IN) can provide a microprocessor logic control signal.
Note:
Connect pin POK to GND when the Power-Ok feature is not used.
8.5 Thermal-Overload Protection
Integrated thermal-overload protection limits total power dissipation in the AS1341. During continuous thermal-overload conditions, when the
AS1341 junction temperature exceeds T
J
= +145ºC, the internal thermal sensor turns off the pass transistor, allowing the AS1341 to cool down.
When the AS1341 junction temperature cools by 10ºC, the thermal sensor turns the pass transistor on again resulting in a pulsed output.
www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
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AS1341
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9 Application Information
9.1 Adjusting Output Voltage
.
Adjust the output voltage by connecting a voltage-divider from the output to GND
Figure 22. Adjustable Output Voltage Circuit
V
IN
4.5V to 20V
C
IN
5
IN
7
SHDNN
6
ILIMIT
2
GND
AS1341
4
LX
D1
3
POK
1
FB
8
OUT
L1
R
PULL
R
1
R
2
1.25V to V
IN
+
C
OUT
Indicates High-Power Trace
Select a value for R
2
between 10k and 1M
Ω
.
Calculate R
1
as:
R
1
=
R
2
⋅
V
-------------
– 1
V
FB
Where:
V
FB
= 1.25V.
V
OUT
may range from 1.25V to V
IN
.
9.2 Negative Output Voltage
V
IN
may range from 4.5V to (20V-V
OUT
). Therefore the maximum negative output voltage is -15V.
Figure 23. Adjustable Negative Output Voltage Circuit
V
IN
4.5V to (20V-V
OUT)
L1
C
IN
5
IN
7
SHDNN
6
ILIMIT
2
GND
AS1341
4
LX
3
POK
1
FB
8
OUT
D1
R
1
R
2
+
C
OUT
(EQ 2)
V
OUT
= -1.25V to -15V
Indicates High-Power Trace www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
10 - 18
AS1341
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9.3 Setting Current Limit
The AS1341 adjustable peak current limit is set by connecting
Table 4. Setting Peak Current Limit
Current Limit
700mA
1400mA
ILIMIT Connected To
GND
IN
The current limit chosen should reflect the maximum load current. The maximum output current is half of the peak current limit. Choosing a lower current limit allows using an inductor with a lower current rating, however, it requires a higher inductance
(see Inductor Selection) and does not
allow for reduced inductor package size.
9.4 Inductor Selection
The AS1341 operates with a wide range of inductance values. For most applications, values between 10µH and 47µH work best with the controller’s high switching frequency. Larger inductor values will reduce the switching frequency and thereby improve efficiency and EMI.
Note:
The four key factors in inductor selection are inductance value, saturation rating, series resistance, and size.
The trade-off for improved efficiency is a higher output ripple and slower transient response. On the other hand, low-value inductors respond faster to transients, improve output ripple, offer smaller physical size, and minimize cost. If the inductor value is too small, the peak inductor current exceeds the current limit due to current-sense comparator propagation delay, potentially exceeding the inductor’s current rating.
Calculate the minimum inductance value as follows:
L
MIN
= ((V
INMAX
- V
OUTPUT
) x t
ONMIN
/I
LXPEAK
(EQ 3)
Where:
t
ONMIN
= 1µs
The inductor saturation current rating must be greater than the peak switch current limit, plus the overshoot due to the 250ns current-sense comparator propagation delay. Saturation occurs when the magnetic flux density of the inductor reaches the maximum level the core can support and the inductance starts to fall. Choose an inductor with a saturation rating greater than IPEAK in the following equation:
I
PEAK
= (I
LXPEAK
+ (V
IN
- V
OUTPUT
) x 250ns)/L (EQ 4)
Inductor series resistance affects both efficiency and dropout voltage
(see Dropout Voltage on page 9) . High series resistance limits the
maximum current available at lower input voltages, and increases the dropout voltage. For optimum performance, select an inductor with the lowest possible DC resistance that fits in the allotted dimensions.
Table 5. Recommended Inductors
Part Number
MSS6132-103ML
LPS4018-472ML
MSS6132-393ML
LPS4018-223ML
CDRH6D28NP-150
CDRH5D18NP-4R1
CDRH6D28NP-470
CDRH5D18NP-220
LQH66SN-100M03
LQH55DN-150M03
LQH66SN-470M03
LQH55DN-470M03
L
10µH
4.7µH
39µH
22µH
15µH
4.1µH
47µH
22µH
10µH
15µH
47µH
47µH
DCR
85m
Ω
125m
Ω
345m
Ω
360m
Ω
62m
Ω
57m
Ω
176m
Ω
215m
Ω
36m
Ω
150m
Ω
170m
Ω
400m
Ω
Current Rating
1.4A
1.8A
0.8A
0.7A
1.4A
1.95A
0.8A
0.8A
1.6A
1.4A
0.8A
0.8A
Manufacturer
Coilcraft www.coilcraft.com
Sumida www.sumida.com
Murata www.murata.com
www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
11 - 18
AS1341
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9.5 Maximum Output Current
The AS1341 output current determines the regulator’s switching frequency. When the converter approaches continuous mode, the output voltage falls out of regulation. For the typical application, the maximum output current is approximately:
(EQ 5) I
LOADMAX
= 1/2 x I
LXPEAKMIN
For low-input voltages, the maximum on-time may be reached and the load current is limited by:
I
LOAD
= (1/2 x (V
IN
- V
OUT
) x 10µs)/L (EQ 6)
9.6 Output Capacitor
Choose the output capacitor to service the maximum load current with acceptable voltage ripple. The output ripple has two components: variations in the charge stored in the output capacitor with each LX pulse, and the voltage drop across the capacitor’s equivalent series resistance (ESR) caused by the current into and out of the capacitor:
V
RIPPLE
≅
V
RIPPLEESR
+ V
RIPPLEC
(EQ 7)
The output voltage ripple as a consequence of the ESR and output capacitance is:
V
RIPPLEESR
= ESR x I
PEAK
V
RIPPLEC
= (L x (I
PEAK
- I
OUTPUT
)2)/(2 x (C
OUT
x V
OUTPUT
)) x V
IN
/(V
IN
- V
OUTPUT
)
Where:
I
PEAK
is the peak inductor current
(see Inductor Selection on page 11)
. The worst-case ripple occurs at no-load.
(EQ 8)
(EQ 9)
circuit. As a general rule, a smaller amount of charge delivered in each pulse results in less output ripple. Since the amount of charge delivered in each oscillator pulse is determined by the inductor value and input voltage, the voltage ripple increases with larger inductance, and as the input voltage decreases.
Table 6. Recommended Output Capacitor
Part Number
T520V107M010ATE018
A700V826M006ATE018
T520B107M006ATE040
T520A336M006ATE070
A700V226M006ATE028
510X107M020ATE040
EEFUD0J101R
EEFCD0K330R
10TPB100ML
6TPB47M
C
100µF
82µF
100µF
33µF
22µF
10µF
100µF
33µF
100µF
47µF
ESR
18m
Ω
18m
Ω
40m
Ω
70m
Ω
28m
Ω
40m
Ω
15m
Ω
18m
Ω
55m
Ω
70m
Ω
Rated Voltage
10V
6.3V
6V
6.3V
6.3V
20V
6.3V
8V
10V
6.3V
Manufacturer
Kemet www.kemet.com
Panasonic www.panasonic.com
Sanyo www.edc.sanyo.com
www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
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AS1341
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9.7 Input Capacitor
The input filter capacitor reduces peak currents drawn from the power source and reduces noise and voltage ripple on the input caused by the circuit’s switching. The input capacitor must meet the ripple-current requirement (I
RMS
) imposed by the switching current defined as:
I
RMS
= (I
LOAD
x V
OUTPUT
)/V
IN
x
√
((4/3) x (V
IN
- V
OUTPUT
) - 1) (EQ 10)
For most applications, non-tantalum type (ceramic, aluminum, polymer, or OS-CON) are preferred due to their robustness to high in-rush currents typical of systems with low-impedance battery inputs. Alternatively, connect two (or more) smaller value low-ESR capacitors in parallel to reduce cost. Choose an input capacitor that exhibits less than +10ºC temperature rise at the RMS input current for optimal circuit life.
Table 7. Recommended Input Capacitor
C TC Code Rated Voltage
10µF X7R 25V
Manufacturer
Murata www.murata.com
Taiyo Yuden www.t-yuden.com
Kemet www.kemet.com
Panasonic www.panasonic.com
Sanyo www.edc.sanyo.com
9.8 Diode Selection
excessive losses, the diode must have a fast turn-on time and a low forward voltage.
Note:
, and that its breakdown voltage exceeds V
IN
. Schottky diodes are recommended.
9.9 Stable Operation
A well-designed system and selection of high-quality external components can eliminate excessive noise on pins OUT, FB, or GND, which can lead to unstable device operation. Instability typically manifests itself as grouped switching pulses with large gaps and excessive low-frequency output ripple (motorboating) during no-load or light-load conditions.
9.10 Recommended Components
Table 8. Recommended Components
Input Voltage Output Voltage ILIMIT
4.5V to 20V
4.5v to 12V
4.5V to 20V
4.5V to 12V
6V to 20V
1.25V to 5V
1.25V to 5V
5V to V
IN
High
Low
High or Low
Inductor
MSS6132-103ML
LQH66SN-100M03
LQH55DN-150M03
CDRH6D28NP-150
CDRH5D18NP-4R1
LPS4018-472ML
MSS6132-393ML
CDRH6D28NP-470
LQH66SN-470M03
LQH55DN-470M03
MSS6132-103ML
LPS4018-223ML
CDRH5D18NP-220
See Inductors above
Output Capacitor
T520V107M010ATE018
A700V826M006ATE018
T520B107M006ATE040
EEFUD0J101R
10TPB100ML
EEFCD0K330R
6TPB47M
T520A336M006ATE070
A700V226M006ATE028
510X107M020ATE040 www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
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AS1341
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
9.11 PC Board Layout and Grounding
High switching frequencies and large peak currents make PC board layout an important part of AS1341-based designs. Good PCB layout can avoid switching noise being introduced into the feedback path, resulting in jitter, instability, or degraded performance.
- High-power traces (see Figure 22 on page 10) should be as short and wide as possible.
- The current loops formed by the external components (C
IN
, C
OUT
, L1, and D1 see
Figure 22 on page 10 ) should be as short as possible
to avoid radiated noise. Connect the ground pins of these power components at a common node in a star-ground configuration.
- Separate noisy traces, such as the LX node, from the feedback network with grounded copper.
- Keep the extra copper on the PCB and integrate it into a pseudo-ground plane.
- When using external feedback, place the resistors as close to pin FB as possible to minimize noise coupling.
www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
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AS1341
Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s
10 Package Drawings and Markings
Figure 24. TDFN-8 3x3mm Marking
AS1341
XXXX xxx - encoded Datecode www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
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AS1341
Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s
Figure 25. TDFN-8 3x3mm Package
www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
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AS1341
Datasheet - O r d e r i n g I n f o r m a t i o n
11 Ordering Information
The device is available as the standard products shown in
.
Table 9. Ordering Information
Ordering Code Marking
AS1341-BTDT-1k 1341
AS1341-BTDT-6k 1341
Description Delivery Form Package
20V, 600mA, 100% Duty Cycle, Step-Down Converter Tape and Reel 1000 pcs TDFN-8 3x3mm
20V, 600mA, 100% Duty Cycle, Step-Down Converter Tape and Reel 6000 pcs TDFN-8 3x3mm
Note:
All products are RoHS compliant and ams green.
Buy our products or get free samples online at ICdirect: http://www.ams.com/ICdirect
Technical Support is found at http://www.ams.com/Technical-Support
For further information and requests, please contact us mailto:[email protected]
or find your local distributor at http://www.ams.com/distributor www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
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AS1341
Datasheet
Copyrights
Copyright © 1997-2010, ams AG, Tobelbaderstrasse 30, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered ®. All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner.
All products and companies mentioned are trademarks or registered trademarks of their respective companies.
Disclaimer
Devices sold by ams AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. ams AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. ams AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with ams AG for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing by ams AG for each application. For shipments of less than 100 parts the manufacturing flow might show deviations from the standard production flow, such as test flow or test location.
The information furnished here by ams AG is believed to be correct and accurate. However, ams AG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of ams AG rendering of technical or other services.
Contact Information
Headquarters
ams AG
Tobelbaderstrasse 30
A-8141 Unterpremstaetten, Austria
Tel: +43 (0) 3136 500 0
Fax: +43 (0) 3136 525 01
For Sales Offices, Distributors and Representatives, please visit: http://www.ams.com/contact www.ams.com/DC-DC_Step-Up/AS1341 Revision 1.09
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