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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
The AS1321 is a high-efficiency step-up DC-DC converter designed to generate a fixed output voltage of +5.0V. 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). In order to save power the AS1321 features a shutdown mode, where it draws less than 1A. 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. The AS1321 is available in a 6-pin SOT23 package.
2 Key Features
! ! ! ! ! ! ! !
Fixed Output Voltage: +5.0V Output Current: Up to 130mA (@ 2V VBATT) Internal Synchronous Rectifier Shutdown Mode Supply Current: Less Than 1A 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
!
3 Applications
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
5 OUT COUT 22F
+5.0V Output R1 100k RESETN Output
+1.5V to +5.0V Battery CIN 22F
4 L1 10H LX
AS1321
6 RESETN
On Off
1 SHDNN
3 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
6
RESETN
BATT
2
AS1321
5
OUT
GND
3
4
LX
Pin Descriptions
Table 1. Pin Descriptions Name SHDNN BATT GND LX OUT RESETN Pin Number 1 2 3 4 5 6 Description Active-Low Logic Shutdown Input 0 = The AS1321 is off and the current into BATT is 1A (typ). 1 = The AS1321 is on. Battery Voltage Input Ground External Inductor Connection Output Voltage 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 All Pins to GND LX Current Latch-Up Package Power Dissipation (TAMB = +70C) Operating Temperature Range Electrostatic Discharge Humidity (Non-Condensing) Storage Temperature Range Junction Temperature -40 -500 5 -55 -100 Min -0.3 Max 7 1 100 500 +85 +500 85 125 150 Units V A mA mW C V % C C 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". HBM MIL-Std. 883E 3015.7 methods JEDEC 78 (JA = 9.1mW/C above +70C) Comments
Package Body Temperature
260
C
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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 +85C, VBATT = +2V, VOUT = +5.0, VSHDNN = +1.5V (unless otherwise specified). Typ values @ TAMB = +25C. Table 3. Electrical Characteristics Parameter Battery Input Range Startup Battery Input Voltage Output Voltage
2 1
Symbol VBATT VSU VOUT RNCH RPCH
1
Conditions RLOAD = 100, TAMB = +25C RLOAD = 100, TAMB = -40 to +85C TAMB = +25C TAMB = -40 to +85C ILX = 100mA, TAMB = +25C ILX = 100mA, TAMB = -40 to +85C ILX = 100mA, TAMB = +25C ILX = 100mA, TAMB = -40 to +85C TAMB = +25C TAMB = -40 to +85C TAMB = +25C TAMB = -40 to +85C TAMB = +25C TAMB = -40 to +85C VOUT = +5.5V, TAMB = +25C VOUT = +5.5V, TAMB = -40 to +85C VSHDNN = 0V, TAMB = +25C VSHDNN = 0V, TAMB = -40 to +85C VOUT = +5.5V, TAMB = +25C VOUT = +5.5V, TAMB = -40 to +85C VSHDNN = 0V, TAMB = +25C VSHDNN = 0V, TAMB = -40 to +85C VBATT = +1.5 to +5.0V Rising Edge, TAMB = +25C Rising Edge, TAMB = -40 to +85C Falling Edge, TAMB = +25C Falling Edge, TAMB = -40 to +85C IRESETN = 1mA, VOUT = +2.5V, TAMB = +25C IRESETN = 1mA, VOUT = +2.5V, TAMB = -40 to +85C VRESETN = +5.5V, TAMB = +25C VRESETN = +5.5V, TAMB = +85C TAMB = +25C TAMB = +85C
Min 1.5
Typ 1.22 1.24
Max 5.0 1.5 5.050 5.125 1.2 1.5 1.3 1.6 850 950 9 10 60 65 55 60 1 2 1 2 1 2 0.3
Unit V V V mA s mA A A A A V V V
4.950 4.875
5.000 0.3 0.4
N-Channel On-Resistance P-Channel On-Resistance N-Channel Switch Current Limit Switch Maximum On-Time Synchronous Rectifier Zero-Crossing Current Quiescent Current into OUT
3
IMAX tON
550 450 5 4 8 0
700 7 30 35 0.01 0.01 0.01
Shutdown Current into OUT Quiescent Current into BATT
3
Shutdown Current into BATT SHDNN Logic Low
1
SHDNN Threshold SHDNN Threshold Hysteresis RESETN Threshold
1.185 1.170
1.228 0.02
1.271 1.286
4.288 4.242
4.500
4.712 4.758 0.15
V
RESETN Voltage Low
V 0.2 0.1 1 0.1 10 130 91 1000 100 nA nA mA %
RESETN Leakage Current LX Leakage Current Maximum Load Current Efficiency ILOAD
VBATT = +2V VBATT = +3V, ILOAD = 100mA
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 = +25C (unless otherwise specified). Figure 3. Efficiency vs. Load Current
100
Figure 4. Efficiency vs. Input Voltage
100
95
VBATT = 4.5V VBATT = 3V VBATT = 2.5V
90
Efficiency (%)
90
Efficiency (%)
VBATT = 3.5V
80
85
VBATT = 2V VBATT = 1.5V
70
80
60
Iout = 1mA Iout = 10mA Iout = 100mA
75 1 10 100 1000
50 1 2 3 4 5
Load Current (mA) Figure 5. VOUT vs. VBATT; On, 39
6 5
Battery Voltage (V) Figure 6. VOUT vs. VBATT; On, 470
6 5
Output Voltage (V)
4 3 2 1 0 0 1 2 3 4 5
Output Voltage (V)
4 3 2 1 0 0 1 2 3 4 5
Battery Voltage (V) Figure 7. VOUT vs. VBATT; Shutdown, 130mA Load
6 5
Battery Voltage (V) Figure 8. VOUT vs. VBATT; Shutdown, no Load
6 5
Output Voltage (V)
4 3 2 1 0 1.5 2 2.5 3 3.5 4 4.5 5
Output Voltage (V)
4 3 2 1 0 0 1 2 3 4 5
Battery Voltage (V) www.austriamicrosystems.com Revision 1.02
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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
400
Figure 10. Startup Voltage vs. Load Resistance
5
Maximum Output Current (mA)
350 4 250 200 150 100 50 0 1.5 2 2.5 3 3.5 4 4.5 5 0 10 100 1000 10000
Supply Voltage (V) Battery Voltage (V)
300
3
2
1
Load Resistance (Ohm)
Figure 11. Input Current vs. Input Voltage
400
Iout = 4A
Figure 12. Waveforms; RLOAD = 100, VBATT = 3V
Input Current (A)
300 250 200 150
VOUT
350
Iout = 34A
50 0 1 2 3 4 5
10s/Div
Battery Voltage (V)
Figure 13. Line Transient
Figure 14. Load Transient
100mV/Div
1V/Div
130mA IOUT 2mA
VIN
100s/Div
500s/Div
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100mV/Div
VOUT
VOUT
500mA/Div
100
IL
2V/Div
VLX
50mV/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
Figure 15. On / Off Response; RLOAD = 100
Figure 16. Shutdown Response; RLOAD = 100
1V/Div
VOUT
1V/Div
VSHDNN
VOUT
2ms/Div
500s/Div
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2V/Div
VIN
1V/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 35A 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 22F
4 10H LX
Zero Crossing Detector Startup Circuitry Driver and Control Logic
5 OUT COUT 22F
+5.0V Output
- + +1.228V
2 BATT 1 SHDNN
Current Limiter
VREF
-
6 RESETN
AS1321
GND 3
+1.1V
+
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 7s 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
+1.5 to +5.0V Battery CIN 22F
2 BATT
5 OUT R3 100k COUT 22F
+5.0V Output
4 R1 220k L1 10H LX
AS1321
6 RESETN
Power-On Reset
1 R2 1M 10nF SHDNN
3 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 The value of R2 should be between 100k and 1M 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. (EQ 1)
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 100k to 1M 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 47H; 10H 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) (1s))/0.7A < L < (VBATT(MIN)(7s))/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 (0.3 typ). Note: Coils should be able to handle 500mARMS and have a ISAT 1A and should have a RIND 100m. (EQ 2) (EQ 3)
Capacitor Selection
COUT Selection
Choose a COUT value to achieve the desired output ripple percentage. A 22F ceramic capacitor is a good initial value. The value for COUT can be determined by: COUT > (L + 2.5H) x VBATT(MAX) / (r% x 4) Where: r is the desired output ripple in %.
2
(EQ 4)
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. min and is located above pin 1. 6. Meets JEDEC MO178.
Symbol A A1 A2 b C D E E1 L e
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 0 10
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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 AS1321-T Marking ASKX Description 130mA Step-Up DC-DC Converter Delivery Form Tape and Reel Package 6-pin SOT23
Note: All products are RoHS compliant and Pb-free. Buy our products or get free samples online at ICdirect: http://www.austriamicrosystems.com/ICdirect For further information and requests, please contact us mailto:sales@austriamicrosystems.com or find your local distributor at http://www.austriamicrosystems.com/distributor
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AS1321
Datasheet
Copyrights
Copyright (c) 1997-2009, austriamicrosystems AG, Tobelbaderstrasse 30, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered (R). 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. The information furnished here by austriamicrosystems AG is believed to be correct and accurate. However, austriamicrosystems 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 austriamicrosystems AG rendering of technical or other services.
Contact Information
Headquarters austriamicrosystems 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.austriamicrosystems.com/contact
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