A S1 3 2 2
L o w Vo lt a g e, M i c ro p o w e r, D C- DC St ep - U p C o n v e r te r s
1 General Description
The AS1322A and the AS1322B are synchronous, fixed frequency,
very high-efficiency DC-DC boost converters capable of supplying
3.3V at 150mA from a single AA-supply. Compact size and minimum
external parts requirements make these devices perfect for modern
portable devices.
High-speed switching frequency (1.2MHz) and internally
compensated PWM current mode design provide highly-reliable DC-
DC conversion, especially when driving white LEDs.
The converters are available as the standard products listed in
Table
1.
Table 1. Standard Products
Model
AS1322A
AS1322B
Light Load Switching
Automatic Powersave Operation
Continuous Switching
2 Key Features
95% Efficiency
Single-Cell Operation
Delivers 160mA @ 3.3V (from Single AA Cell)
Delivers 220mA @ 5.0V (from Two AA Cells)
Delivers 570mA @ 3.3V (from Two AA Cells)
Low Start-Up Voltage: 0.85V
High-Speed Fixed-Frequency: 1.2MHz
Internal PMOS Synchronous Rectifier
Automatic Powersave Operation (AS1322A)
Continuous Switching at Light Loads (AS1322B)
Anti-Ringing Control Minimizes EMI
Logic Controlled Shutdown (< 1µA)
Output Range: 2.5 to 5.0V
6-pin TSOT-23 Package
The devices contain two internal MOSFET switches: one NMOS
switch and one PMOS synchronous rectifier.
Anti-ringing control circuitry reduces EMI by damping the inductor in
discontinuous mode, and the devices exhibit extremely low
quiescent current (< 1µA) in shutdown.
In shutdown mode the battery is connected to the output and V
OUT
is held at approximately V
IN
- 0.6V.
The AS1322 is available in a 6-pin TSOT-23 package.
3 Applications
The AS1322 is ideal for low-power applications where ultra-small
size is critical as in medical diagnostic equipment, hand-held
instruments, pagers, digital cameras, remote wireless transmitters,
MP3 players, LCD bias supplies, cordless phones, GPS receivers,
and PC cards.
Figure 1. Typical Application Diagram – Single Cell to 3.3V
Synchronous Boost Converter
L1
4.7µH
1
AA Battery
C
1
10µF
6
V
IN
SW
5
V
OUT
C
2
10µF
V
OUT
3.3V
160mA
AS1322
4
SHDNN
2
GND
3
FB
R
1
1.02MΩ
1%
On
Off
R
2
604kΩ
1%
www.ams.com/DC-DC_Step-Up/AS1322
Revision 1.10
1 - 18
AS1322
Datasheet - P i n A s s i g n m e n t s
4 Pin Assignments
Figure 2. Pin Assignments (Top View)
SW 1
6
VIN
GND 2
AS1322
5
VOUT
FB 3
4 SHDNN
4.1 Pin Descriptions
Table 2. Pin Descriptions
Pin Number
Pin Name
Description
Switch Pin.
Connect an inductor between this pin and V
IN
. Keep the PCB trace lengths as
short and wide as is practical to reduce EMI and voltage overshoot. If the inductor current
falls to zero, or pin SHDNN is low, an internal 100Ω anti-ringing switch is connected from this
pin to V
IN
to minimize EMI.
Note:
An optional Schottky diode can be connected between this pin and V
OUT
.
Signal and Power Ground.
Provide a short, direct PCB path between this pin and the
negative side of the output capacitor(s).
Feedback Pin.
Feedback input to the g
m
error amplifier. Connect a resistor divider tap to this
pin. The output voltage can be adjusted from 2.5 to 5V by: V
OUT
= 1.23V[1 + (R
1
/R
2
)]
Shutdown Pin.
Logic controlled shutdown input.
1 = Normal operation, 1.2MHz typical operating frequency.
0 = Shutdown; quiescent current <1µA. If SHDNN is undefined, pin SW may ring.
Note:
In a typical application, SHDNN should be connected to V
IN
through a 1MΩ pull-up
resistor.
Output Voltage Sense Input and Drain of the Internal PMOS Synchronous Rectifier.
Bias is derived from V
OUT
when V
OUT
exceeds V
IN
. PCB trace length from V
OUT
to the
output filter capacitor(s) should be as short and wide as is practical. V
OUT
is held at
approximately V
IN
- 0.6V during shutdown.
Input Voltage.
The AS1322 gets its start-up bias from V
IN
unless V
OUT
exceeds V
IN
, in
which case the bias is derived from V
OUT
. Thus, once started, operation is completely
independent from V
IN
. Operation is only limited by the output power level and the internal
series resistance of the supply.
1
SW
2
3
GND
FB
4
SHDNN
5
VOUT
6
VIN
www.ams.com/DC-DC_Step-Up/AS1322
Revision 1.10
2 - 18
AS1322
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 3
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
Section 6 Electrical Characteristics on page 4
is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Table 3. Absolute Maximum Ratings
Parameter
VIN to GND
SHDNN, SW to GND
FB to GND
VOUT
Operating Temperature Range
Storage Temperature Range
Min
-0.3
-0.3
-0.3
-0.3
-40
-65
Max
7
7
5
7
+85
+125
Units
V
V
V
V
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 an unlimited floor life time
Notes
Package Body Temperature
+260
ºC
Moisture Sensitive Level
1
www.ams.com/DC-DC_Step-Up/AS1322
Revision 1.10
3 - 18
AS1322
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
T
AMB
= -40 to +85ºC,
V
IN
= +1.2V, V
OUT
= +3.3V,
V
SHDNN
= +1.2V (unless otherwise specified). Typ values @ T
AMB
= +25ºC.
Table 4. Electrical Characteristics
Symbol
Parameter
Minimum Start-Up Voltage
Minimum Operating Voltage
Output Voltage Adjust Range
V
FB
I
FB
I
QPWS
I
QSHDNN
I
Q
I
NMOSSWL
I
PMOSSWL
R
ONNMOS
Feedback Voltage
Feedback Input Current
Quiescent Current
(Powersave Operation)
Quiescent Current (Shutdown)
Quiescent Current (Active)
NMOS Switch Leakage
PMOS Switch Leakage
NMOS Switch On Resistance
Conditions
I
LOAD
= 1mA
SHDNN = V
IN
T
AMB
= 25ºC
T
AMB
=
T
MIN
to T
MAX
V
FB
= 1.25V
3
2
1
Min
Typ
0.85
0.65
Max
1
0.85
5
Units
V
V
V
V
nA
2.5
1.192
1.23
1
30
0.01
150
0.1
0.1
0.35
0.20
0.45
0.30
850
2
1.268
V
FB
= 1.4V , AS1322A only
V
SHDNN
= 0V
V
FB
= 1.4V , AS1322B only
V
SW
= 5V
V
SW
= 0V
V
OUT
= 3.3V
V
OUT
= 5V
V
OUT
= 3.3V
V
OUT
= 5V
V
IN
= 2.5V
AS1322A only
3
50
1
300
5
5
0.8
0.7
0.8
0.7
µA
µA
µA
µA
µA
Ω
Ω
mA
mA
%
R
ONPMOS
I
NMOS
I
PS
PMOS Switch On Resistance
NMOS Current Limit
Powersave Operation Current
Threshold
Max Duty Cycle
3
80
0.95
0.85
1
0.35
87
1.2
1.2
1.5
1.5
V
FB
= 1V, T
AMB
=
T
MIN
to T
MAX
T
AMB
= 25ºC
T
AMB
=
T
MIN
to T
MAX
f
SW
V
SHDNNH
V
SHDNNL
I
SHDNN
Switching Frequency
SHDNN Input High
SHDNN Input Low
SHDNN Input Current
MHz
V
V
µA
V
SHDNN
= 5.0V
0.01
1
1. Minimum V
IN
operation after start-up is only limited by the battery’s ability to provide the necessary power as it enters a deeply dis-
charged state.
2. Specification is guaranteed by design and not 100% production tested.
3. I
QPWS
is measured at V
OUT
. Multiply this value by V
OUT
/V
IN
to get the equivalent input (battery) current.
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/AS1322
Revision 1.10
4 - 18
AS1322
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
Figure 3. Powersave mode threshold vs. V
IN
,
V
OUT
= 3.0V
30
25
Figure 4. Efficiency vs. Output Current,
V
OUT
= 3.3V
100
90
VIN = 2.4V
VIN = 1.5V
Output Current (mA)
.
20
15
10
5
0
0.5 0.75
1
1.25 1.5 1.75
2
2.25 2.5
Efficiency (%)
.
80
70
VIN = 1.0V
60
50
40
30
1
10
100
1000
Battery Voltage (V)
Output Current (mA)
Figure 5. Output Voltage vs. Temperature;
V
OUT
= 3.3V, I
OUT
= 10mA
3.36
3.34
Figure 6. Output Voltage vs. Battery Voltage;
V
OUT
= 3.3V, I
OUT
= 10mA
3.5
3
Output Voltage (V)
.
Output Voltage (V)
.
-25
0
25
50
75
100
3.32
3.3
3.28
3.26
3.24
-50
2.5
2
1.5
1
0.5
0
0
0.5
1
1.5
2
2.5
3
3.5
Temperature (°C)
Battery Voltage (V)
Figure 7. Startup Voltage vs. Output Current;
1.6
1.5
Figure 8. Output Current vs. Battery Voltage;
V
OUT
= 3.3V, 3% Tolerance
1000
900
Startup Voltage (V)
.
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.1
1
10
100
5V
3.3V
.
Output Current (mA)
800
700
600
500
400
300
200
100
0
0.5
1
1.5
2
2.5
3
Output Current (mA)
Battery Voltage (V)
www.ams.com/DC-DC_Step-Up/AS1322
Revision 1.10
5 - 18
嵌入式系统
