AMSCO AS1321_1

Da t as heet
AS1321
1 3 0 m A St e p - U p D C - D C C o n v e r t e r
1 General Description
2 Key Features
The AS1321 is a high-efficiency step-up DC-DC converter designed to generate a fixed output voltage of
+5.0V.
!
Fixed Output Voltage: +5.0V
!
Output Current: Up to 130mA (@ 2V VBATT)
The AS1321 achieves an efficiency of up to 96%. The
minimum input voltage is +1.5V, the output voltage is
fixed at +5.0V, and output current is up to 130mA
(@ 2V VBATT).
!
Internal Synchronous Rectifier
!
Shutdown Mode Supply Current: Less Than 1µA
!
Efficiency: Up to 96%
!
Minimum Input Voltage: +1.5V
!
Accurate Shutdown Low-Battery Cutoff Threshold
!
Battery Input Connected to Pin OUT in Shutdown
Mode for Backup Power
!
6-pin SOT23 Package
In order to save power the AS1321 features a shutdown
mode, where it draws less than 1µA. In shutdown mode
the battery is connected directly to the output enabling
the supply of real-time-clocks.
The AS1321 provides a power-on reset output that goes
high-impedance when the output reaches 90% of its regulation point.
The SHDNN trip threshold of the AS1321 can be used
as an input voltage detector that disables the device
when the battery voltage falls to a predetermined level.
An internal synchronous rectifier is included, which is
parallel with the external Schottky diode.
3 Applications
The AS1321 is available in a 6-pin SOT23 package.
The AS1321 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, cordless phones, and PC
cards.
The device is also perfect as a local +5.0V supply or as
a battery backup.
Figure 1. AS1321 - Typical Application Diagram
2
BATT
4
+1.5V to +5.0V
Battery
L1
10µH
CIN
22µF
On
Off
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LX
+5.0V
Output
5
OUT
AS1321
1
6
RESETN
COUT
22µF
R1
100kΩ
RESETN
Output
3
SHDNN
GND
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AS1321
Datasheet - P i n o u t
4 Pinout
Pin Assignments
Figure 2. Pin Assignments (Top View)
SHDNN
1
BATT
2
GND
3
AS1321
6
RESETN
5
OUT
4
LX
Pin Descriptions
Table 1. Pin Descriptions
Name
Pin Number
Description
SHDNN
1
Active-Low Logic Shutdown Input
0 = The AS1321 is off and the current into BATT is ≤ 1µA (typ).
1 = The AS1321 is on.
BATT
2
Battery Voltage Input
GND
3
Ground
LX
4
External Inductor Connection
OUT
5
Output Voltage
RESETN
6
Active-Low reset output
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AS1321
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 Section 6 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
Min
Max
Units
All Pins to GND
-0.3
7
V
1
A
-100
100
mA
JEDEC 78
500
mW
(ΘJA = 9.1mW/ºC above +70ºC)
LX Current
Latch-Up
Package Power Dissipation
(TAMB = +70ºC)
Operating Temperature Range
-40
+85
ºC
Electrostatic Discharge
-500
+500
V
Humidity (Non-Condensing)
5
85
%
Storage Temperature Range
-55
125
ºC
150
ºC
Junction Temperature
Package Body Temperature
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260
ºC
Revision 1.02
Comments
HBM MIL-Std. 883E 3015.7 methods
The reflow peak soldering temperature (body
temperature) specified is in compliance with
IPC/JEDEC J-STD-020D “Moisture/ Reflow
Sensitivity Classification for Non-Hermetic
Solid State Surface Mount Devices”.
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AS1321
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
TAMB = -40 to +85ºC, VBATT = +2V, VOUT = +5.0, VSHDNN = +1.5V (unless otherwise specified). Typ values @ TAMB = +25ºC.
Table 3. Electrical Characteristics
Parameter
Symbol
Battery Input Range
VBATT
1
Startup Battery Input Voltage
Output Voltage
VSU
2
VOUT
N-Channel
On-Resistance
RNCH
P-Channel On-Resistance
RPCH
N-Channel Switch Current Limit
Switch Maximum
On-Time
1
IMAX
tON
Synchronous Rectifier
Zero-Crossing Current
Quiescent Current into OUT
Min
Typ
1.5
RLOAD = 100Ω, TAMB = +25ºC
1.22
RLOAD = 100Ω, TAMB = -40 to +85ºC
1.24
TAMB = +25ºC
4.950
TAMB = -40 to +85ºC
4.875
ILX = 100mA, TAMB = +25ºC
5.000
0.3
ILX = 100mA, TAMB = +25ºC
0.4
ILX = 100mA, TAMB = -40 to +85ºC
TAMB = +25ºC
550
TAMB = -40 to +85ºC
450
TAMB = +25ºC
5
TAMB = -40 to +85ºC
4
TAMB = +25ºC
8
TAMB = -40 to +85ºC
0
700
7
1.2
1.3
850
9
30
60
65
55
60
0.01
1
2
VOUT = +5.5V, TAMB = +25ºC
0.01
1
2
VSHDNN = 0V, TAMB = +25ºC
SHDNN Threshold
5.050
10
VOUT = +5.5V, TAMB = -40 to +85ºC
1
1.5
950
35
VSHDNN = 0V, TAMB = +25ºC
Shutdown Current into BATT
V
1.6
VSHDNN = 0V, TAMB = -40 to +85ºC
3
Unit
5.0
1.5
VOUT = +5.5V, TAMB = -40 to +85ºC
Quiescent Current into BATT
Max
5.125
ILX = 100mA, TAMB = -40 to +85ºC
VOUT = +5.5V, TAMB = +25ºC
3
Shutdown Current into OUT
SHDNN Logic Low
Conditions
0.01
1
VSHDNN = 0V, TAMB = -40 to +85ºC
2
VBATT = +1.5 to +5.0V
0.3
Rising Edge, TAMB = +25ºC
1.185
Rising Edge, TAMB = -40 to +85ºC
1.170
SHDNN Threshold Hysteresis
1.228
1.271
1.286
0.02
RESETN Threshold
RESETN Voltage Low
RESETN Leakage Current
LX Leakage Current
Falling Edge, TAMB = +25ºC
4.288
Falling Edge, TAMB = -40 to +85ºC
4.242
4.500
V
V
Ω
Ω
mA
µs
mA
µA
µA
µA
µA
V
V
V
4.712
4.758
IRESETN = 1mA, VOUT = +2.5V,
TAMB = +25ºC
0.15
IRESETN = 1mA, VOUT = +2.5V,
TAMB = -40 to +85ºC
0.2
V
V
VRESETN = +5.5V, TAMB = +25ºC
0.1
VRESETN = +5.5V, TAMB = +85ºC
1
TAMB = +25ºC
0.1
TAMB = +85ºC
10
100
1000
nA
nA
Maximum Load Current
ILOAD
VBATT = +2V
130
mA
Efficiency
η
VBATT = +3V, ILOAD = 100mA
91
%
1. Guaranteed by design.
2. Voltage which triggers next loading cycle. Ripple and rms value depend on external components.
3. The Quiescent current is measured while the DC-DC Converter is not switching.
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AS1321
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
VBATT = 2.0V, VOUT = 5.0V, TAMB = +25°C (unless otherwise specified).
Figure 3. Efficiency vs. Load Current
Figure 4. Efficiency vs. Input Voltage
100
100
95
90
VBATT = 4.5V
Efficiency (%)
Efficiency (%)
VBATT = 3.5V
VBATT = 3V
90
VBATT = 2.5V
VBATT = 2V
85
80
70
VBATT = 1.5V
80
Iout = 1mA
60
Iout = 10mA
Iout = 100mA
75
50
1
10
100
1000
1
2
Load Current (mA)
4
5
Figure 6. VOUT vs. VBATT; On, 470Ω
6
6
5
5
Output Voltage (V)
Output Voltage (V)
Figure 5. VOUT vs. VBATT; On, 39Ω
4
3
2
1
4
3
2
1
0
0
0
1
2
3
4
5
0
1
Battery Voltage (V)
2
3
4
5
Battery Voltage (V)
Figure 7. VOUT vs. VBATT; Shutdown, 130mA Load
Figure 8. VOUT vs. VBATT; Shutdown, no Load
6
6
5
5
Output Voltage (V)
Output Voltage (V)
3
Battery Voltage (V)
4
3
2
1
4
3
2
1
0
0
1.5
2
2.5
3
3.5
4
4.5
5
0
Battery Voltage (V)
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1
2
3
4
5
Battery Voltage (V)
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AS1321
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. Maximum Output Current vs. VBATT
Figure 10. Startup Voltage vs. Load Resistance
5
350
4
300
Supply Voltage (V)
Maximum Output Current (mA)
400
250
200
150
100
3
2
1
50
0
0
1.5
2
2.5
3
3.5
4
4.5
5
10
Battery Voltage (V)
100
1000
10000
Load Resistance (Ohm)
Figure 12. Waveforms; RLOAD = 100Ω, VBATT = 3V
Figure 11. Input Current vs. Input Voltage
400
VOUT
300
2V/Div
250
VLX
Input Current (µA)
Iout = 34µA
50mV/Div
Iout = 4µA
350
200
150
IL
500mA/Div
100
50
0
1
2
3
4
5
10µs/Div
Battery Voltage (V)
VOUT
2mA
IOUT
1V/Div
VOUT
VIN
130mA
100µs/Div
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100mV/Div
Figure 14. Load Transient
100mV/Div
Figure 13. Line Transient
500µs/Div
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AS1321
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
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1V/Div
VOUT
VSHDNN
2ms/Div
2V/Div
1V/Div
Figure 16. Shutdown Response; RLOAD = 100Ω
1V/Div
VIN
VOUT
Figure 15. On / Off Response; RLOAD = 100Ω
500µs/Div
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AS1321
Datasheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
The AS1321 is a high-efficiency, compact step-up converter with 35µA quiescent supply current which ensures the
highest efficiency over a wide load range. With a minimum of +1.5V input voltage, the device is well suited for applications with one- or two-cells, such as lithium ion (Li+), nickel-metal-hydride (NiMH), or alkaline.
Figure 17. AS1321 - Block Diagram
+1.5 to +5.0V
Battery
CIN
22µF
Zero
Crossing
Detector
4
10µH
LX
5
OUT COUT
22µF
+5.0V
Output
Startup
Circuitry
Driver
and
Control
Logic
–
+
2
BATT
+1.228V
VREF
Current
Limiter
–
1
AS1321
SHDNN
GND
+1.1V
+
6
RESETN
3
The input battery is connected to the device through an inductor and an internal P-FET when pin SHDNN is low. In this
state, the step-up converter is off and the voltage drop across the P-FET body diode is eliminated, and the input battery can be used as a battery-backup or real-time-clock supply.
The built-in synchronous rectifier significantly improves efficiency.
Control Circuitry
The AS1321 integrated current-limited key circuitry provides low quiescent current and extremely-high efficiency over
a wide VOUT range without the need for an oscillator. Inductor current is limited by the 7µs switch maximum on-time or
by the 0.7A N-channel current limit. At each cycle, the inductor current must ramp down to zero after the on-time
before the next cycle may start. When the error comparator senses that the output has fallen below the regulation
threshold, another cycle begins.
Shutdown
When pin SHDNN is low the AS1321 is switched off and no 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
VOUT to avoid intermittently switching the device on.
Note: If pin SHDNN is not used, it should be connected directly to pin OUT.
In shutdown the battery input is connected to the output through the inductor and the internal synchronous rectifier PFET. This allows the input battery to provide backup power for devices such as an idle microcontroller, memory, or realtime-clock, without the usual diode forward drop. In this way a separate backup battery is not needed.
In cases where there is residual voltage during shutdown, some small amount of energy will be transferred from pin
OUT to pin BATT immediately after shutdown, resulting in a momentary spike of the voltage at pin BATT. The ratio of
CIN and COUT partly determine the size and duration of this spike, as does the current-sink ability of the input device.
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AS1321
Datasheet - D e t a i l e d D e s c r i p t i o n
Low-Battery Cutoff
The AS1321 SHDNN trip threshold (1.228V) can be used as an input voltage detector that disables the device when
the battery input voltage falls to a pre-set level. An external resistor-divider network can be used to set the batterydetection voltage (see Figure 18).
Figure 18. Low-Battery Cutoff Application Diagram
2
+1.5 to +5.0V
Battery
5
BATT
OUT
CIN
22µF
R3
100kΩ
4
R1
220kΩ
L1
10µH
LX
AS1321
RESETN
1
R2
1MΩ
10nF
6
COUT
22µF
+5.0V
Output
Power-On
Reset
3
SHDNN
GND
For the resistor-divider network shown in Figure 18, calculate the value for R1 by:
R1 = R2 x ((VOFF/VSHDNN) - 1)
Where:
VOFF is the battery voltage at which the AS1321 shuts down.
VSHDNN = 1.228V
(EQ 1)
The value of R2 should be between 100kΩ and 1MΩ to minimize battery drain.
Note: Input ripple can cause false shutdowns, therefore to minimize the effect of ripple, a low-value capacitor from
SHDNN to GND should be used to filter out input noise. The value of the capacitor should be such that the R/C
time constant is > 2ms.
Power-On Reset
The AS1321 provides a power-on reset output (RESETN) that goes high-impedance when the output reaches 90% of
its regulation point. RESETN goes low when the output is below 90% of the regulation point. A 100kΩ to 1MΩ pullup
resistor between pin RESETN and pin OUT can provide a microprocessor logic control signal.
Note: Connect pin RESETN to GND when the power-on reset feature is not used.
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AS1321
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
Inductor Selection
The control circuitry of the AS1321 permits a wide range of inductor values to be selected – from 4.7 to 47µH; 10µH is
ideal for most applications.
The intended application should dictate the value of L. The trade-off between required PCB surface area and desired
output ripple are the determining factors: smaller values for L require less PCB space, larger values of L reduce output
ripple. If the value of L is large enough to prevent IMAX from being reached before tON expires, the AS1321 output
power will be reduced.
For maximum output current calculate the value for L as:
(VBATT(MAX) (1µs))/0.7A < L < (VBATT(MIN)(7µs))/0.7A
IOUT(MAX) = (0.7A/2)(VBATT(MIN) - (0.7A/2)(RNCH + RIND))/VOUT
Where:
RIND is the inductor series resistance.
RNCH is the RDS(ON) of the N-channel MOSFET (0.3Ω typ).
(EQ 2)
(EQ 3)
Note: Coils should be able to handle 500mARMS and have a ISAT ≥ 1A and should have a RIND ≤ 100mΩ.
Capacitor Selection
COUT Selection
Choose a COUT value to achieve the desired output ripple percentage. A 22µF ceramic capacitor is a good initial value.
The value for COUT can be determined by:
2
COUT > (L + 2.5µH) x VBATT(MAX) / (r% x 4)
(EQ 4)
Where:
r is the desired output ripple in %.
CIN Selection
CIN reduces the peak current drawn from the battery and can be the same value as COUT. A larger value for CIN can be
used to further reduce ripple and improve AS1321 efficiency.
External Diode
An external Schottky diode must be connected, in parallel with the on-chip synchronous rectifier, from LX to OUT. Use
diodes such as MBR0520L, EP05Q03L, or the generic 1N5817. The diode should be rated for 500mA, since it carries
current during startup and after the synchronous rectifier turns off. The Schottky diode must be connected as close to
the IC as possible. Ordinary rectifier diodes must not be used, since the slow recovery rate will compromise efficiency.
PC Board Layout and Grounding
Well-designed printed circuit-board layout is important for minimizing ground bounce and noise.
!
Place pin GND lead and the ground leads of CIN and COUT as close to the device as possible.
!
Keep the lead to pin LX as short as possible.
!
To maximize output power and efficiency and minimize output ripple voltage, use a ground plane and solder the
GND pin directly to the ground plane.
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AS1321
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
The AS1321 is available in a 6-pin SOT23 package.
Figure 19. 6-pin SOT23 Package
Notes:
1. All dimensions are in millimeters.
2. Foot length is measured at the intercept point between datum
A and lead surface.
3. Package outline exclusive of mold flash and metal burr.
4. Pin 1 is the lower left pin when reading the top mark from left
to right.
5. Pin 1 identifier dot is 0.3mm.φ min and is located above pin 1.
6. Meets JEDEC MO178.
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Revision 1.02
Symbol
A
A1
A2
b
C
D
E
E1
L
e
α
Min
Max
0.90
1.45
0.00
0.15
0.90
1.30
0.35
0.50
0.08
0.20
2.80
3.00
2.60
3.00
1.50
1.75
0.35
0.55
0.95 REF
0º
10º
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AS1321
Datasheet - O r d e r i n g I n f o r m a t i o n
11 Ordering Information
The AS1321 is available as the standard products shown in Table 4.
Table 4. Ordering Information
Ordering Code
Marking
Description
Delivery Form
Package
AS1321-T
ASKX
130mA Step-Up DC-DC Converter
Tape and Reel
6-pin SOT23
Note: All products are RoHS compliant and Pb-free.
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AS1321
Datasheet
Copyrights
Copyright © 1997-2009, austriamicrosystems 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 austriamicrosystems AG are covered by the warranty and patent indemnification provisions appearing
in its Term of Sale. austriamicrosystems 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.
austriamicrosystems 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 austriamicrosystems 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
austriamicrosystems 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.
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Tobelbaderstrasse 30
A-8141 Unterpremstaetten, Austria
Tel: +43 (0) 3136 500 0
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