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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 0.4Ω 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 light-
load 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.
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 0.4Ω 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
Figure 1. AS1341 - Typical Application
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
5
IN
4
LX
D1
L1
V
OUT
= 5V
C
IN
7
SHDNN
6
ILIMIT
8
C
OUT
+
AS1341
OUT
R
PULL
3
POK
1
FB
Indicates High-Power Trace
2
GND
www.ams.com/DC-DC_Step-Up/AS1341
Revision 1.09
1 - 18
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
8 OUT
7 SHDNN
AS1341
POK 3
LX 4
9
6 ILIMIT
5 IN
4.1 Pin Descriptions
Table 1. Pin Descriptions
Pin Number
1
2
3
4
5
6
7
8
9
Pin Name
FB
GND
POK
LX
IN
ILIMIT
SHDNN
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
(see Setting
Current Limit on page 11).
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.
www.ams.com/DC-DC_Step-Up/AS1341
Revision 1.09
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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
Stresses beyond those listed in
Table 2
may cause permanent damage to the device. These are stress ratings only, and functional operation of
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
LX to GND
FB to GND
ILIMIT, SHDNN, OUT, POK to GND
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
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).
Represents a max. floor life time of unlimited
on PCB
-0.3
-2
-0.3
-0.3
+23
V
IN
+ 0.3
+5
V
IN
+ 0.3
2
V
V
V
V
A
Min
Max
Units
Comments
Package Body Temperature
+260
ºC
Humidity non-condensing
Moisture Sensitive Level
5
1
85
%
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Revision 1.09
3 - 18
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
Figure 1
on page 1.
Table 3. Electrical Characteristics
Symbol
T
AMB
V
IN
V
OUT
V
DROPOUT
Parameter
Operating Temperature Range
Input Voltage Range
Output Voltage (Preset Output)
Output Voltage (Adjustable)
Dropout Voltage
Line Regulation
Load Regulation
V
FB
I
IN
I
INDROP
Feedback Set Voltage (Adjustable
Output)
Input Supply Current
Input Supply Current in Dropout
Input Shutdown Current
V
UVLO
Input Undervoltage Lockout
Threshold
OUT Bias Current
I
FB
FB Bias Current
FB Threshold Low
Thermal Shutdown
DC-DC Switches
t
OFFMIN
t
ONMAX
R
LX
I
LXPEAK
LX Switch Minimum Off-Time
LX Switch Maximum On-Time
LX Switch On-Resistance
LX Current Limit
LX Zero-Crossing Threshold
Zero-Crossing Timeout
LX Switch Leakage Current
Control Inputs
Digital Input Level
Digital Input Leakage Current
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
SHDNN, ILIMIT = GND
SHDNN, ILIMIT = IN
V
SHDNN
, V
ILIMIT
= 0 to 20V, V
IN
= 20V
2.4
-100
+100
0.8
V
nA
LX does not rise above the threshold
V
IN
= 20V, LX = GND, T
AMB
= +25ºC
V
IN
= 20V, LX = GND
V
FB
= 1.3V
V
IN
= 6V
V
IN
= 4.5V
ILIMIT = GND, L = 39µH
ILIMIT = IN, L = 10µH
500
1000
-75
30
0.1
1
0.2
8
0.4
10
0.4
0.5
700
1400
900
1800
+75
0.6
12
µs
µs
Ω
mA
mV
µs
µA
10ºC hysteresis
No load
No load
SHDNN = GND
V
IN
rising
V
IN
falling
V
OUT
= 5.5V
V
FB
= 1.3V
3.6
3.5
2
-25
50
100
145
I
OUT
= 600mA, ILIMIT = V
IN
V
IN
= 6V to 20V, 200Ω load
ILIMIT = V
IN
, I
OUT
= 0 to 500mA
1.212
FB = GND
Conditions
Min
-45
4.5
4.85
1.25
250
0.1
1
1.25
12
45
0.8
4.0
3.9
3.5
1.288
18
60
3
4.4
4.3
5
+25
150
5.00
Typ
Max
85
20
5.15
V
IN
Units
°C
V
V
mV
%/V
%
V
µA
µA
µA
V
µA
nA
mV
ºC
Note:
All limits are guaranteed. The parameters with min and max values are guaranteed with production tests or SQC (Statistical Quality
Control) methods.
www.ams.com/DC-DC_Step-Up/AS1341
Revision 1.09
4 - 18
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
95
90
ILIMIT = high
V
IN
= 6V
V
IN
= 12V
Figure 4. Efficiency vs. I
OUT
100
95
90
ILIMIT = low
V
IN
= 6V
V
IN
= 12V
V
IN
= 20V
Efficiency (%)
.
85
80
75
70
65
60
55
50
0.1
1
10
100
1000
V
IN
= 20V
Efficiency (%)
.
85
80
75
70
65
60
55
50
0.1
1
10
100
1000
Output Current (mA)
Output Current (mA)
Figure 5. Efficiency vs. I
OUT
; V
OUT
= 3.3V
100
95
90
V
IN
= 4.5V
ILIMIT = high
Figure 6. Efficiency vs. I
OUT
; V
OUT
= 3.3V
100
95
90
ILIMIT = low
V
IN
= 4.5V
V
IN
= 12V
V
IN
= 20V
Efficiency (%)
.
Efficiency (%)
.
85
80
75
70
65
60
55
50
0.1
1
10
100
1000
V
IN
= 12V
V
IN
= 20V
85
80
75
70
65
60
55
50
0.1
1
10
100
1000
Output Current (mA)
Output Current (mA)
Figure 7. Efficiency vs. I
OUT
; V
IN
= 12V
95
90
ILIMIT = high
Figure 8. Efficiency vs. I
OUT
; V
IN
= 12V
95
90
ILIMIT = low
Efficiency (%)
.
85
80
75
70
65
0.1
1
10
100
1000
22uH
10uH
4.1uH
Efficiency (%)
.
85
80
75
70
65
0.1
1
10
100
1000
10uH
39uH
22uH
Output Current (mA)
Output Current (mA)
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Revision 1.09
5 - 18
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