www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 1 - 18
AS1322
Low Volt age, Micropower, DC-DC Step-Up Conv e r ter 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.
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.
Figure 1. Typical Application Diagram – Single Cell to 3.3V
Synchronous Boost Converter
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
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.
Table 1. Standard Products
Model Light Load Switching
AS1322A Automatic Powersave Operation
AS1322B Continuous Switching
AA Battery
AS1322
C2
10µF
R2
604kΩ
1%
R1
1.02MΩ
1%
On
Off
L1
4.7µH
C1
10µF
GND
2
SW
1
VOUT
3.3V
160mA
4
SHDNN
3
FB
6
VIN
5
VOUT
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 2 - 18
AS1322
Datasheet - P i n Ass i g n me n t s
4 Pin Assignments
Figure 2. Pin Assignments (Top View)
4.1 Pin Descriptions
Table 2. Pin Descriptions
Pin Number Pin Name Description
1SW
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
.
2GND Signal and Power Ground. Provide a short, direct PCB path between this pin and the
negative side of the output capacitor(s).
3FB 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
)]
4SHDNN
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.
5VOUT
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.
6 VIN
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
AS1322
2
GND
3
FB
6VIN
5VOUT
4SHDNN
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 3 - 18
AS1322
Datasheet - A b s o lu t e M ax i m u m R a t i n gs
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 Min Max Units Notes
VIN to GND -0.3 7 V
SHDNN, SW to GND -0.3 7 V
FB to GND -0.3 5 V
VOUT -0.3 7 V
Operating Temperature Range -40 +85 ºC
Storage Temperature Range -65 +125 ºC
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).
Moisture Sensitive Level 1 Represents an unlimited floor life time
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 4 - 18
AS1322
Datasheet - E l e c tr i c a l C h a r act e r is 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.
Note: All limits are guaranteed. The parameters with min and max values are guaranteed with production tests or SQC (Statistical Quality
Control) methods.
Table 4. Electrical Characteristics
Symbol Parameter Conditions Min Typ Max Units
Minimum Start-Up Voltage I
LOAD
= 1mA 0.85 1 V
Minimum Operating Voltage SHDNN = V
IN
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.
0.65 0.85 V
Output Voltage Adjust Range T
AMB
= 25ºC 2.5 5 V
V
FB
Feedback Voltage T
AMB
= T
MIN
to T
MAX
1.192 1.23 1.268 V
I
FB
Feedback Input Current V
FB
= 1.25V
2
2. Specification is guaranteed by design and not 100% production tested.
1 nA
I
QPWS
Quiescent Current
(Powersave Operation) V
FB
= 1.4V
3
, AS1322A only
3. I
QPWS
is measured at V
OUT
. Multiply this value by V
OUT
/V
IN
to get the equivalent input (battery) current.
30 50 µA
I
QSHDNN
Quiescent Current (Shutdown) V
SHDNN
= 0V 0.01 1 µA
I
Q
Quiescent Current (Active) V
FB
= 1.4V
3
, AS1322B only 150 300 µA
I
NMOSSWL
NMOS Switch Leakage V
SW
= 5V 0.1 5 µA
I
PMOSSWL
PMOS Switch Leakage V
SW
= 0V 0.1 5 µA
R
ONNMOS
NMOS Switch On Resistance V
OUT
= 3.3V 0.35 0.8 Ω
V
OUT
= 5V 0.20 0.7
R
ONPMOS
PMOS Switch On Resistance V
OUT
= 3.3V 0.45 0.8 Ω
V
OUT
= 5V 0.30 0.7
I
NMOS
NMOS Current Limit V
IN
= 2.5V 850 mA
I
PS
Powersave Operation Current
Threshold AS1322A only
2
3 mA
Max Duty Cycle V
FB
= 1V, T
AMB
= T
MIN
to T
MAX
80 87 %
f
SW
Switching Frequency T
AMB
= 25ºC 0.95 1.2 1.5 MHz
T
AMB
= T
MIN
to T
MAX
0.85 1.2 1.5
V
SHDNNH
SHDNN Input High 1 V
V
SHDNNL
SHDNN Input Low 0.35 V
I
SHDNN
SHDNN Input Current V
SHDNN
= 5.0V 0.01 1 µA
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 5 - 18
AS1322
Datasheet - Ty p i c al O p e ra t i n g C h a ra c t e r is t i c s
7 Typical Operating Characteristics
Figure 3. Powersave mode threshold vs. V
IN
, Figure 4. Efficiency vs. Output Current,
V
OUT
= 3.0V V
OUT
= 3.3V
Figure 5. Output Voltage vs. Temperature; Figure 6. Output Voltage vs. Battery Voltage;
V
OUT
= 3.3V, I
OUT
= 10mA V
OUT
= 3.3V, I
OUT
= 10mA
Figure 7. Startup Voltage vs. Output Current; Figure 8. Output Current vs. Battery Voltage;
V
OUT
= 3.3V, 3% Tolerance
30
40
50
60
70
80
90
100
1 10 100 1000
Output Current (mA)
Efficiency (%) .
0
5
10
15
20
25
30
0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5
Battery Voltage (V)
Output Current (mA) .
VIN = 2.4V
VIN = 1.5V
VIN = 1.0V
0
0.5
1
1.5
2
2.5
3
3.5
0 0.5 1 1.5 2 2.5 3 3.5
Battery Voltage (V)
Output Voltage (V) .
3.24
3.26
3.28
3.3
3.32
3.34
3.36
-50 -25 0 25 50 75 100
Temperature (°C)
Output Voltage (V) .
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
0.1 1 10 100
Output Current (mA)
Startup Voltage (V) .
5V
3.3V
0
100
200
300
400
500
600
700
800
900
1000
0.5 1 1.5 2 2.5 3
Battery Voltage (V)
Output Current (mA) .
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 6 - 18
AS1322
Datasheet - Ty p i c al O p e ra t i n g C h a ra c t e r is t i c s
Figure 9. Output Current vs. Battery Voltage; Figure 10.
No Load Battery Current vs. V
BATT
V
OUT
= 5.0V, 3% ToleranceV
OUT
= 3.3V, T
AMB
= 25ºC
Figure 11. SW Pin Antiringing Operation Figure 12.
SW Pin Fixed Frequency Continuous Current
V
IN
= 1.3V, V
OUT
= 3.3V, L = 10µH, C = 10µF, I
OUT
= 5mA
V
IN
= 1.3V, V
OUT
= 3.3V, L = 10µH, C = 10µF, I
OUT
= 100mA
Figure 13. V
OUT
Transient Response. Figure 14. Fixed Frequency vs. Powersave Operation
V
IN
= 1.3V, V
OUT
= 3.3V, L = 10µH, C = 10µF V
IN
= 1.3V, V
OUT
= 3.3V, L = 10µH, C = 10µF
Parts used for measurements: 10µH (MOS6020-103ML) Inductor, 10µF (GRM31CR70J106KA01L) C
IN
and C
OUT
10
100
1000
1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3
Battery Voltage (V)
Battery Current (µA) .
0
100
200
300
400
500
600
700
800
900
0.5 1 1.5 2 2.5 3 3.5 4
Battery Voltage (V)
Output Current (mA) .
100ns/Div
VSW
0V 1V/Div
100ns/Div
VSW
0V 1V/Div
100µs/Div
VOUT(AC)
IOUT
40mA 100mA 100mV/Div
10ms/Div
VOUT(AC)
IOUT
1mA 60mA 100mV/Div
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 7 - 18
AS1322
Datasheet - D e t a il e d D es c r i pt i o n
8 Detailed Description
The AS1322/AS1322B can operate from a single-cell input voltage (V
IN
) below 1V, and feature fixed frequency (1.2MHz) and current mode
PWM control for exceptional line- and load-regulation. With low R
DS(ON)
and gate charge internal NMOS and PMOS switches, the devices
maintain high-efficiency from light to heavy loads.
Modern portable devices frequently spend extended time in low-power or standby modes, switching to high power-drain only when certain
functions are enabled. The AS1322A and the AS1322B are ideal for portable devices since they maintain high-power conversion efficiency over
a wide output power range, thus increasing battery life in these types of devices.
In addition to high-efficiency at moderate and heavy loads, the AS1322A includes an automatic powersave mode that improves efficiency of the
power converter at light loads. The powersave mode is initiated if the output load current falls below a factory programmed threshold (see Figure
3 on page 5).
Note: The AS1322B does not support powersave mode and provides continuous operation at light loads, eliminating low-frequency V
OUT
ripple at the expense of light load efficiency.
Figure 15. AS1322 - Block Diagram
8.1 Low-Voltage Start-Up
The AS1322 requires V
IN
of only 0.85V (typ) or higher to start up. The low-voltage start-up circuitry controls the internal NMOS switch up to a
maximum peak inductor current of 850mA (typ), with 1.5ms (approx.) off-time during start-up, allowing the devices to start up into an output load.
With a V
OUT
> 2.3V, the start-up circuitry is disabled and normal fixed-frequency PWM operation is initiated. In this mode, the AS1322 operates
independent of V
IN
, allowing extended operating time as the battery can drop to several tenths of a volt without affecting output regulation. The
limiting factor for the application is the ability of the battery to supply sufficient energy to the output.
AS1322
+
–
Start Up
OSC
PWM
Control
A/B
MUX
Slope
Compensator
1.2MHz
Ramp
Generator
+
–
Powersave
Operation
Control
–
Shutdown
Control
PWM
Comp
Σ
+
–
1.23V
Ref
Sync Drive
Control
A
B
VOUT
Good
2.3V
gm Error
Amp
Shutdown
Powersave
0.35Ω0.45Ω
R2
640kΩ 1%
R1
1.02MΩ
1%
CFF*
COUT
4.7µF
3.3V
Output
CIN
1µF
1.5V
Single Cell
* Optional
Current
Sense
RC
80kΩCP2
2.5pFCC
150pF
GND
2
SW
1
4
SHDNN
3
FB
6
VIN 5
VOUT
L1
4.7µH
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 8 - 18
AS1322
Datasheet - D e t a il e d D es c r i pt i o n
8.2 Low-Noise Fixed-Frequency Operation
8.2.1 Oscillator
The AS1322 switching frequency is internally fixed at 1.2MHz allowing the use of very small external components.
8.2.2 Error Amplifier
The integrated error amplifier is an internally compensated trans-conductance (g
m
) type (current output). The internal 1.23V reference voltage is
compared to the voltage at pin FB to generate an error signal at the output of the error amplifier. A voltage divider from V
OUT
to GND programs
the output voltage from 2.5 to 5V via pin FB as:
V
OUT
= 1.23V(1 + (R
1
/R
2
)) (EQ 1)
8.2.3 Current Sensing
A signal representing the internal NMOS-switch current is summed with the slope compensator. The summed signal is compared to the error
amplifier output to provide a peak current control command for the PWM. Peak switch current is limited to approximately 850mA independent of
V
IN
or V
OUT
.
8.2.4 Zero Current Comparator
The zero current comparator monitors the inductor current to the output and shuts off the PMOS synchronous rectifier once this current drops to
20mA (approx.). This prevents the inductor current from reversing polarity and results in improved converter efficiency at light loads.
8.2.5 Anti-Ringing Control
Anti-ringing control circuitry prevents high-frequency ringing on pin SW as the inductor current approaches zero. This is accomplished by
damping the resonant circuit formed by the inductor and the capacitance on pin SW (C
SW
).
8.3 Powersave Operation (AS1322A)
In light load conditions, the integrated powersave feature removes power from all circuitry not required to monitor V
OUT
. When V
OUT
has
dropped approximately 1% from nominal, the AS1322A powers up and begins normal PWM operation.
C
OUT
(see Figure 15 on page 7) recharges, causing the AS1322A to re-enter powersave mode as long as the output load remains below the
powersave threshold. The frequency of this intermittent PWM is proportional to load current; i.e., as the load current drops further below the
powersave threshold, the AS1322A turns on less frequently. When the load current increases above the powersave threshold, the AS1322A will
resume continuous, seamless PWM operation.
Notes:
1. An optional capacitor (C
FF
) between pins V
OUT
and FB in some applications can reduce V
OUTp-p
ripple and input quiescent current
during powersave mode. Typical values for C
FF
range from 15 to 220pF.
2. In powersave mode the AS1322A draws only 30µA from the output capacitor(s), greatly improving converter efficiency.
8.4 Shutdown
When pin SHDNN is low the AS1322 is switched off and <1µA current is drawn from battery; when pin SHDNN is high the device is switched on.
If SHDNN is driven from a logic-level output, the logic high-level (on) should be referenced to V
OUT
to avoid intermittently switching the device
on.
Note: If pin SHDNN is not used, it should be connected directly to pin OUT. V
OUT
is held at approximately V
IN
- 0.6V during shutdown.
In shutdown the battery input is connected to the output through the inductor and the internal synchronous rectifier P-FET. Due to the body diode
of the internal synchronous rectifier PFET, V
OUT
is held at approximately V
IN
- 0.6V during shutdown. This allows the input battery to provide
backup power for devices such as an idle microcontroller, memory, or real-time-clock, without the usual diode forward drop. In this way a
separate backup battery is not needed.
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 9 - 18
AS1322
Datasheet - A p p l ic a t i o n I n f or m a t i on
9 Application Information
The AS1322 is perfectly suited for LED matrix displays, bar-graph displays, instrument-panel meters, dot matrix displays, set-top boxes, white
goods, professional audio equipment, medical equipment, industrial controllers to name a few applications.
Along with Figure 1 on page 1, Figures 16-19 depict a few of the many applications for which the AS1322 converters are perfectly suited.
Figure 16. Single AA Cell to 3.3V Synchronous Boost Converter with Load Disconnect in Shutdown
Figure 17. Single Lithium Cell to 5V, 250mA
AS1322
C2
4.7µF
R2
604kΩ
1%
On
Off
Q1
L1
4.7µH
AA
Battery C1
4.7µF
R3
510kΩ
R3
510kΩ
VOUT
3.3V, 160mA
D1
R1
1.02MΩ
1%
GND
2
SW
1
4
SHDNN
3
FB
6
VIN
5
VOUT
AS1322
C2
4.7µF
R2
332kΩ 1%
R1
1.02MΩ 1%
On
Off
L1
4.7µH
Lithium
Battery C1
4.7µF
D1
C3
100pF
100nF
2Ω
Optional
Snubber
GND
2
SW
1
4
SHDNN
3
FB
6
VIN
5
VOUT
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 10 - 18
AS1322
Datasheet - A p p l ic a t i o n I n f or m a t i on
Figure 18. Single AA Cell to ±3V Synchronous Boost Converter
Figure 19. Single AA Cell to 2.5V Synchronous Boost Converter
AS1322
R2
750kΩ
1%
R1
1.02MΩ
1%
On
Off
L1
4.7µH
AA
Battery C1
4.7µF
C3
1µF
D1
VOUT2
-3V, 10mA
VOUT1
3V, 90mA
C2
4.7µF
C4
10µF
D2
GND
2
SW
1
4
SHDNN
3
FB
6
VIN
5
VOUT
AS1322
C2
10µF
R2
1.02MΩ
1%
R1
1.02MΩ
1%
On
Off
L1
4.7µH
AA
Battery C1
10µF
VOUT
2.5V, 230mA
D1
GND
2
SW
1
4
SHDNN
3
FB
6
VIN
5
VOUT
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 11 - 18
AS1322
Datasheet - A p p l ic a t i o n I n f or m a t i on
9.1 Output Voltage Ripple
The AS1322 is designed to work at high efficiency. In order to reduce the output ripple the following improvements are recommended:
Use a higher output capacitor, up to 44µF and a higher input capacitor (22µF).
Use smaller values for the resistor divider. R1 should be about 300kΩ. To avoid a high leakage current from pin VOUT through the resistor
divider to GND, R1 should not be less than 100kΩ.
To reduce the output ripple it’s also possible to speed up the feedback loop. To achieve this, place a 22pF (C4 in Figure 20) capacitor in
parallel to R1. Via C4 the fast transients are shorted to the FB pin and the feedback loop is even faster. A 1MΩ resistor for R1 slows down
the FB loop.
Due to noise and to their non linear behavior, the use of potentiometers is not recommended.
Figure 20. AS1322 - Typical Application for lower Output Voltage Ripple
Note: For correct measurements of the output ripple connect the oscilloscope probe as close as possible to the positive plate of the C
OUT
and connect the GND of the oscilloscope probe to the negative plate of the C
OUT
. This will reduce the inductive coupling and will
deliver a more accurate measurement result.
The output ripple is getting higher as V
IN
is getting closer to V
OUT
. Figure 21 shows that the above mentioned improvements reduce the output
voltage ripple. If V
IN
is higher than V
OUT
the AS1322 stops switching and V
IN
is connected to V
OUT
via the inductor and the internal P-FET.
Figure 21. Output Voltage Ripple vs. Input Voltage; V
OUT
= 2.8V, I
OUT
= 0.8mA
AS1322
C2
22µF
R2
196kΩ
R1
250kΩ
On
Off
L1
4.7µH
2xAA Battery
C1
22µF
VOUT = 2.8V
GND
2
SW
1
4
SHDNN
3
FB
5
VOUT C3
22µF
C4
22pF
6
VIN
0
25
50
75
100
125
0.5 1 1.5 2 2.5 3 3.5
Input Voltage (V)
Output Voltage Ripple (mVpp)
Cout = 44µF
Cout = 66µF
Cout = 44µF + C4 = 22pF
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 12 - 18
AS1322
Datasheet - A p p l ic a t i o n I n f or m a t i on
9.2 External Component Selection
9.2.1 Inductor Selection
The fast switching frequency (1.2MHz) of the AS1322 allows for the use of small surface mount or chip inductor for the external inductor (see
Figure 15 on page 7).
The required minimum values for the external inductor are:
3.3µH for applications ≤ 3.6V
4.7µH for applications > 3.6V
Larger inductor values allow greater output current capability by reducing the inductor ripple current. Increasing the inductance above 10µH will
increase size while providing negligible improvement in output current capability.
The approximate output current capability of the AS1322 versus inductor value is given in:
Where:
η is the estimated efficiency;
I
P
is the peak current limit value (0.6A);
V
IN
is the input voltage;
D is the steady-state duty ratio = (V
OUT
- V
IN
)/V
OUT
;
f is the switching frequency (1.2MHz typ);
L is the inductor value.
The inductor current ripple is typically set for 20 to 40% of the maximum inductor current (I
P
). High-frequency ferrite core inductor materials
reduce frequency dependent power losses compared to less expensive powdered iron types, which result in improved converter efficiency.
The inductor should have low ESR to reduce the I
2
R power losses, and must be able to handle the peak inductor current without saturating.
Molded chokes and some chip inductors normally do not have enough core to support the peak inductor currents of the AS1322 (850mA typ). To
minimize radiated noise, use a toroid, pot core, or shielded bobbin inductor.
Table 5. Recommended Inductors
Part Number L DCR Current Rating Dimensions (L/W/T) Manufacturer
MOS6020-103ML 10µH 93mΩ1A 6.8x6.0x2.4mm Coilcraft
www.coilcraft.com
MOS6020-472ML 4.7µH 50mΩ1.5A 6.8x6.0x2.4mm
MOS6020-332ML 3.3µH 46mΩ1.8A 6.8x6.0x2.4mm
CDRH4D18-100 10µH 200mΩ0.61A 6.9x5.0x2.0mm Sumida
www.sumida.com
CDRH4D18-6R8 6.8µH 200mΩ0.76A 6.9x5.0x2.0mm
CR43-6R8 6.8µH 131.2mΩ0.95A 4.8x4.3x3.5mm
CDRH4D18-4R7 4.7µH 162mΩ0.84A 6.9x5.0x2.0mm
(EQ 2)
I
OUT MAX( )
ηI
P
V
IN
D⋅
f L 2⋅ ⋅
------------------
–
1 D–( )⋅ ⋅=
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 13 - 18
AS1322
Datasheet - A p p l ic a t i o n I n f or m a t i on
Figure 22. Efficiency Comparison of Different Inductors, V
IN
= 1.5V, V
OUT
= 3.3V
9.2.2 Output Capacitor Selection
Low ESR capacitors should be used to minimize V
OUT
ripple. Multi-layer ceramic capacitors are recommended since they have extremely low
ESR and are available in small footprints. A 2.2 to 10µF output capacitor is sufficient for most applications. Larger values up to 22µF may be
used to obtain extremely low output voltage ripple and improve transient response.
An additional phase lead capacitor may be required with output capacitors larger than 10µF to maintain acceptable phase margin. X5R and X7R
dielectric materials are recommended due to their ability to maintain capacitance over wide voltage and temperature ranges.
Input Capacitor Selection.
Low ESR input capacitors reduce input switching noise and reduce the peak current drawn from the battery.
Ceramic capacitors are recommended for input decoupling and should be located as close to the device as is practical. A 4.7µF input capacitor
is sufficient for most applications. Larger values may be used without limitations.
Diode Selection.
A Schottky diode should be used to carry the output current for the time it takes the PMOS synchronous rectifier to switch
on. For V
OUT
< 4.5V a Schottky diode is optional, although using one will increase device efficiency by 2 to 3%.
Note: Do not use ordinary rectifier diodes, since the slow recovery times will compromise efficiency.
Table 6. Recommended Output Capacitor
Part Number C TC Code Rated Voltage Dimensions (L/W/T) Manufacturer
JMK212BJ226MG-T 22µF ±20% X5R 6.3V 2x1.3x1.3mm Taiyo Yuden
www.t-yuden.com
Table 7. Recommended Input Capacitor
Part Number C TC Code Rated Voltage Dimensions (L/W/T) Manufacturer
GRM31CR70J106KA01L 10µF ±10% X7R 6.3V 3.2x1.6x1.6mm Murata
www.murata.com
Ser ies8
40
45
50
55
60
65
70
75
80
85
90
0.1 1 10
Output Current (mA)
Efficiency (%)
10uH - Coilcr af t (MOS6020-103ML)
10uH - Sumida(CDRH4D18-100)
6.8uH - Sumida(CDRH4D18-6R8)
6.8uH - Sumida(CR43-6R8)
4.7uH - Coil cr af t(MOS6020-472M L)
4.7 uH - Sumida(CDRH4D18-4R7)
3.3 uH - Coilcr af t(MOS6020-332ML)
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 14 - 18
AS1322
Datasheet - A p p l ic a t i o n I n f or m a t i on
9.3 PCB Layout Guidelines
The high-speed operation of the AS1322 requires proper layout for optimum performance. Figure 23 shows the recommended component
layout.
A large ground pin copper area will help to lower the device temperature.
A multi-layer board with a separate ground plane is recommended.
Traces carrying large currents should be direct.
Trace area at pin FB should be as small as is practical.
The lead-length to the battery should be as short as is practical.
Figure 23. Recommended Single-Layer Component Placement
1
AS1322
2
3
6
5
4
Optional
SHDNN
VIN
FB
VOUT
GND
SW
VOUT
VIN
SHDNN
R2
R1COUT
CIN
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 15 - 18
AS1322
Datasheet - P a c k a ge D raw i n g s a n d Ma r k i n gs
10 Package Drawings and Markings
The device is available in a 6-pin TSOT-23 package.
Figure 24. 6-pin TSOT-23 Package
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 16 - 18
AS1322
Datasheet - P a c k a ge D raw i n g s a n d Ma r k i n gs
Figure 25. 6-pin TSOT-23 Marking
ZZZZ XXXX
Top Bottom
Pin1
Pin1
Package Code:
ZZZZ - Marketingcode
XXXX - encoded Datecode
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 17 - 18
AS1322
Datasheet
11 Ordering Information
The device is available as the standard products listed in Table 8.
Note: All products are RoHS compliant.
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:sales@ams.com
or find your local distributor at http://www.ams.com/distributor
Table 8. Ordering Information
Ordering Code Marking Description Delivery Form Package
AS1322A-BTTT ASKQ Low Voltage, Micropower, DC-DC Step-Up Converter with
Automatic Powersave Operation Tape and Reel 6-pin TSOT-23
AS1322B-BTTT ASKZ Low Voltage, Micropower, DC-DC Step-Up Converter with
Continuous Switching Tape and Reel 6-pin TSOT-23
www.ams.com/DC-DC_Step-Up/AS1322 Revision 1.10 18 - 18
AS1322
Datasheet - O r d e r in g Inf o r m a ti o n
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