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Da t as heet
AS1337
2 0 0 m A , D C - D C St e p - U p C o n v e r t e r w i t h B u c k M o d e
1 General Description
The AS1337 is a synchronous, fixed frequency, highefficiency DC-DC boost converter capable of supplying 3.3V @ 200mA from two AA Cells. Compact size and minimum external parts requirements make these devices perfect for modern portable devices. The AS1337 offers automatic powersave mode to increase efficiency at light loads. For input voltages higher than VOUT the AS1337 will switch in a step down mode, so that a Buck Boost function is realized. The AS1337A offers a shutdown mode where the battery is connected directly to the output enabling the supply of real-time-clocks or memories. The AS1337 offers a POK (open-drain) feature which detects output power fail of 10%. The AS1337 is available in a TDFN (3x3mm) 8-pin package.
2 Key Features
! ! ! ! ! ! ! ! ! ! ! !
Input Voltage Range: 0.65V to 4.5V Low Start-Up Voltage: 0.85V Output Voltage Range: 2.5V to 5.0V Delivers 200mA @ 3.3V (from two AA Cell) up to 97% Efficiency High-Speed Fixed-Frequency: 1.2MHz Single-Cell Operation Internal PMOS Synchronous Rectifier Automatic Powersave Operation Anti-Ringing Control Minimizes EMI Logic Controlled Shutdown (< 1A) TDFN (3x3mm) 8-pin Package
3 Applications
The AS1337 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. AS1337 - Typical Application Diagram - Dual Cell to 3.3V Synchronous Boost Converter
3.6V Buck Mode VOUT=3.3V 2x AA Cell Range VIN Curve Boost Mode
L1 4.7H VIN = 2xAA 1.6V to 3.6V CIN 10F
On Off
VOUT = 3.3V LX VIN VOUT FB COUT 22F
AS1337
EN GND
POK PGND
1.6V
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AS1337
Datasheet - P i n A s s i g n m e n t s
4 Pin Assignments
Figure 2. Pin Assignments (Top View)
VOUT 1 LX 2
8 FB 7 VIN
AS1337
PGND 3 GND 4 6 POK 5 EN
9 GND
Pin Descriptions
Table 1. Pin Descriptions Pin Name VOUT Pin Number 1 Description Output Voltage. Bias is derived from VOUT when VOUT exceeds VIN. PCB trace length from VOUT to the output filter capacitor(s) should be as short and wide as is practical. Switch Pin. Connect an inductor between this pin and VIN. 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 EN is low, an internal 100 anti-ringing switch is connected from this pin to VIN to minimize EMI. Note: An optional Schottky diode can be connected between this pin and VOUT. Power Ground. Provide a short, direct PCB path between this pin and the output capacitor(s). Ground Enable Pin. Logic controlled enable input. 1 = Normal operation 0 = Shutdown Note: In a typical application, EN should be connected to VIN through a 1M pull-up resistor. POK. High when VOUT is within regulation. Input Voltage. The AS1337 gets its start-up bias from VIN unless VOUT exceeds VIN, in which case the bias is derived from VOUT. Thus, once started, operation is completely independent from VIN. Operation is only limited by the output power level and the internal series resistance of the supply. Feedback Pin. Feedback input to the gm error amplifier. Connect a resistor divider tap to this pin. The output voltage can be adjusted from 2.5V to 5V by: VOUT = 1.23V[1 + (R1/R2)] Exposed Pad Ground
LX
2
PGND GND
3 4
EN
5
POK VIN
6 7
FB GND
8 9
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AS1337
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 VIN to GND FB to GND All other pins to GND Operating Temperature Range Storage Temperature Range Min -0.3 -0.3 -0.3 -40 -65 Max 5.5 5 6 +85 +125 Units V V V C C The reflow peak soldering temperature (body temperature) specified is in accordance with IPC/JEDEC J-STD020D "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). @85C, JEDEC 78 HBM MIL-Std. 883E 3015.7 methods Notes
Package Body Temperature
+260
C
Latch-Up Human Body Model
-100 2
100
mA kV
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AS1337
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
VIN = VEN = +1.2V, VOUT = +3.3V, Typ values @ TAMB = +25C, TAMB = -40 to +85C (unless otherwise specified); Table 3. Electrical Characteristics Symbol Input Minimum Start-Up Voltage Minimum Operating Voltage VIN Maximum Input Voltage Output Voltage Adjust Range Regulation VFB IFB Feedback Voltage Feedback Input Current VFB = 1.25V
2
Parameter
Conditions ILOAD = 1mA EN = VIN
1
Min
Typ
Max
Units
0.85 0.65
1.15 0.85 4.5
V V V V
2.5
5
1.192
1.23 1
1.268
V nA
Operating Current IQPWS ISHDN Switches INMOSSWL NMOS Switch Leakage RONNMOS NMOS Switch On Resistance VOUT = 3.3V VOUT = 5V VOUT = 3.3V VOUT = 5V 0.01 0.35 0.20 0.45 0.30 850 VFB = 1V 80 0.95 87 1.2 1.5 1 A mA % MHz Quiescent Current Shutdown Current VFB = 1.4V 20 0.01 35 1 A A
EN = GND, VIN = 3.3V
RONPMOS PMOS Switch On Resistance INMOS NMOS Current Limit Max Duty Cycle fSW Shutdown VIH VIL IEN Power-OK POK Voltage Low POK Leakage Current Power-OK Threshold Thermal Protection TENM TENM Overtemperature Protection Overtemperature Protection Hysteresis EN Input Current Enable Input Threshold Switching Frequency
1 0.3 EN = 5.0V 0.01 1
V A
IPOK=1mA VPOK = VIN or VOUT Falling Edge 86
0.1 1 88
0.4 100 91
V nA %
145 10
C C
1. Minimum VIN operation after start-up is only limited by the battery's ability to provide the necessary power as it enters a deeply discharged state. 2. IQPWS is measured at VOUT. Multiply this value by VOUT/VIN to get the equivalent input (battery) current.
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AS1337
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
VOUT = 3.3V, CIN = 10F, COUT = 22F, L1 = 4.7H, TAMB = +25C (unless otherwise specified). Figure 3. Efficiency vs. IOUT - Down Conversion Mode
100 90 80 70 60 50 40 30 0.1 1 10 100 1000
Vin = 3.5V Vin = 4.0V
Figure 4. Efficiency vs. IOUT - Step-up Mode
100 90 80 70 60 50
Vin = 1.5V
Efficiency (%)
Efficiency (%)
40 30 0.1 1 10 100
Vin = 2.0V Vin = 3.0V
1000
Output Current (mA) Figure 5. Efficiency vs. Input Voltage
100 90 80 70 60 50 40 30 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
Iout = 1mA Iout = 10mA Iout = 30mA Iout = 100mA Iout = 200mA
Output Current (mA) Figure 6. Output Current vs. Input Voltage
500
Output Current (mA)
400
Efficiency (%)
300
200
100
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Input Voltage (V) Figure 7. Min. Operating Voltage vs. Temperature
0.85
Input Voltage (V) Figure 8. Switching Frequency vs. Temperature
1.5
Minimum Operating Voltage (V)
Switching Frequency (MHz)
0 15 30 45 60 75 90
0.75
1.4 1.3 1.2 1.1 1 0.9 -45 -30 -15
0.65
0.55
0.45
0.35 -45 -30 -15
0
15
30
45
60
75
90
Temperature (C) www.austriamicrosystems.com Revision 1.03
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AS1337
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. Output Voltage vs. Temp.; ILOAD = 1mA
3.5 3.45
Figure 10. Load Transient Response; VIN = 1.8V
Output Voltage (V)
3.35 3.3
IOUT
VOUT
3.4
3.25 3.2 3.15 3.1 -45 -30 -15
0
15
30
45
60
75
90
1ms/Div
Temperature (C)
Figure 11. Load Transient Response; VIN = 3.0V
Figure 12. Load Transient Response; VIN = 3.6V
100mV/Div
100mA
IOUT
10mA
IOUT
1ms/Div
1ms/Div
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10mA
100mA
100mV/Div
VOUT
VOUT
10mA
100mA
100mV/Div
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AS1337
Datasheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
The AS1337 can operate from a single-cell input voltage (VIN) below 1V, and features fixed frequency (1.2MHz) and current mode PWM control for exceptional line- and load-regulation. With low RDS(ON) and gate charge internal NMOS and PMOS switches, the device maintains high-efficiency from light to heavy loads. Modern portable devices frequently spend extended time in low-power or standby modes, switching to high powerdrain only when certain functions are enabled. The AS1337 is ideal for portable devices since they maintain highpower 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 AS1337 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. The Overtemperature protection circuitry turn-off both switches for a short time when the temperature reaches 145C in the device . Figure 13. AS1337 - Block Diagram
L1 4.7H
4
1 SW
POK
1.5V Single Cell 6 Start Up OSC
VIN CIN 1F
A B
A/B MUX
PWM Control Sync Drive Control 1.2MHz Ramp Generator + PWM - Comp - Slope Compensator
- VOUT Good +
2.3V 5
3.3V Output
VOUT
0.35 Current Sense
0.45 CFF* R1 1.02M 1% COUT 4.7F
4
EN
Shutdown Control
Shutdown
Powersave Operation Control
RC 80k CC 150pF
- gm Error Amp +
3
FB
CP2 2.5pF
1.23V Ref
Powersave
R2 640k 1%
AS1337
2 GND
* Optional
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AS1337
Datasheet - D e t a i l e d D e s c r i p t i o n
Low-Voltage Start-Up and Soft Start
The AS1337 requires a VIN of only 0.85V (typ) or higher to start up. The low-voltage start-up circuitry controls the internal switches and provides a soft start function, where the inductor current during start up is limited to about 300mA. This soft start and in rush current limitation feature provides also a smooth curve of VOUT after start up and makes the overshoot of VOUT minimal. After a certain time a bigger inductor current is allowed and the soft start is disabled.
Low-Noise Fixed-Frequency Operation
Oscillator
The AS1337 switching frequency is internally fixed at 1.2MHz allowing the use of very small external components.
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 VIN or VOUT.
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.
Anti-Ringing Control
Anti-ringing control circuitry prevents high-frequency ringing on pin LX as the inductor current approaches zero. This is accomplished by damping the resonant circuit formed by the inductor and the capacitance on pin LX.
Setting Output Voltage
A voltage divider from VOUT to GND programs the output voltage from 2.5V to 5V via pin FB as: VOUT = 1.23V(1 + (R1/R2)) (EQ 1)
Powersave Operation
In light load conditions, the integrated powersave feature removes power from all circuitry not required to monitor VOUT. When VOUT has dropped approximately 1% from nominal, the AS1337 powers up and begins normal PWM operation. COUT (see Figure 13 on page 7) recharges, causing the AS1337 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 AS1337 turns on less frequently. When the load current increases above the powersave threshold, the AS1337 will resume continuous, seamless PWM operation. Note: An optional capacitor (CFF) between pins VOUT and FB in some applications can reduce VOUTp-p ripple and input quiescent current during powersave mode. Typical values for CFF range from 15pF to 220pF.
Buck Mode
The AS1337A offers a low power buck mode for VIN > VOUT operation.
Shutdown
When pin EN is low the AS1337 is switched off and <1A current is drawn from battery; when pin EN is high the device is switched on. If EN 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 EN is not used, it should be connected directly to pin VOUT. Caution: Because of the feedthrough the output voltage is the same as the input voltage during shutdown. If VIN > VOUT the output voltage will jump to the value of the input voltage when the device switches into shutdown. During normal operation the device is in down conversion mode.
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AS1337
Datasheet - D e t a i l e d D e s c r i p t i o n
Shutdown Battery Feedthrough (AS1337A)
In shutdown the battery input of the AS1337A is connected to the output through the inductor and the small internal synchronous rectifier P-FET. 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.
Future Version (on request): Shutdown Battery Disconnect (AS1337B)
The AS1337B is designed to allow true output disconnect by opening both P-channel MOSFET rectifiers. This means that VOUT is discharged and connected to GND.
POK Function
The POK output indicates if the output voltage is within 88% (typ.) of the nominal voltage level. As long as the output voltage is within regulation the open-drain POK output is high impedance. The POK output can be tied to VIN or to VOUT or to any external voltage up to VIN or VOUT via a pull-up resistance (see Figure 1 on page 1). If the output voltage drops below 88% (typ.) of the nominal voltage the POK pin is pulled to GND. Note: It is important to consider that in shutdown mode the POK output is pulled to VIN in order to save current.
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AS1337
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
The AS1337 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, Figure 14 and Figure 15 depict a few of the many applications for which the AS1337 converters are perfectly suited. Figure 14. Single AA Cell to 3.3V Synchronous Boost Converter
L1 4.7H LX VIN = 1.5V CIN 10F
On Off
VOUT = 3.3V VOUT R1 1.02M R2 640k COUT 22F
VIN
FB
AS1337
POK
EN
GND
PGND
Figure 15. Single Lithium Cell to 5V
L1 4.7H LX Lithium-Ionen Cell CIN 10F
On Off
VOUT = 5.0V VOUT R1 2M R2 640k COUT 22F
VIN
FB
AS1337
POK
EN
GND
PGND
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AS1337
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
Component Selection
Only three power components are required to complete the design of the buck-boost converter, except the additional two resistors for the voltage divider to set VOUT. The high operating frequency and low peak currents of the AS1337 allow the use of low value, low profile inductors and tiny external ceramic capacitors.
Inductor Selection
The inductor should have low ESR to reduce the IR power losses, and must be able to handle the peak inductor current without saturating. High-frequency ferrite core inductor materials reduce frequency dependent power losses compared to less expensive powdered iron types, which result in improved converter efficiency. A 4.7H to 15H inductor value with a >850mA current rating and low DCR is recommended. For applications where radiated noise is a concern, a toroidal or shielded inductor can be used.
Capacitor Selection
A 10F capacitor is recommend for CIN as well as a 22F for COUT. Small-sized ceramic capacitors are recommended. X5R and X7R ceramic capacitors are recommend as they retain capacitance over wide ranges of voltages and temperatures.
Output Capacitor Selection
Low ESR capacitors should be used to minimize VOUT ripple. Multi-layer ceramic capacitors are recommended since they have extremely low ESR and are available in small footprints. A 1 to 10F output capacitor is sufficient for most applications. Larger values up to 22F 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 10F 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 4.7F input capacitor is sufficient for most applications. Larger values may be used without limitations. Table 4. Recommended External Components Name CIN COUT L1 Part Number GRM219R60J106KE19 GRM21BR60J226ME39 MOS6020-472ML Value 10F 22F 4.7H Rating 6.3V 6.3V 1.82A Type X5R X5R 50m Size 0805 0805 Manufacturer Murata www.murata.com
Coilcraft 6.8x6.0x2.4mm www.coilcraft.com
PCB Layout Guidelines
The high-speed operation of the AS1337 requires proper layout for optimum performance.
! ! ! ! !
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.
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AS1337
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 devices are available in a TDFN (3x3mm) 8-pin package. Figure 16. TDFN (3x3mm) 8-pin Package
D D2 SEE DETAIL B B A L E2/2
aaa C 2x PIN 1 INDEX AREA (D/2 xE/2)
D2/2
E2 K N N-1 e (ND-1) X e
BTM VIEW
E
PIN 1 INDEX AREA (D/2 xE/2)
aaa C
2x TOP VIEW
b ddd bbb C CAB
e DETAIL B e/2
Terminal Tip
ccc C
A3
C
SEATING PLANE
0.08 C
A
Datum A or B EVEN TERMINAL SIDE
Symbol A A1 A3 L1 L2 aaa bbb ccc ddd eee ggg Notes:
Min 0.70 0.00 0.03
Typ 0.75 0.02 0.20 REF
Max 0.80 0.05 0.15 0.13
0.15 0.10 0.10 0.05 0.08 0.10
Notes 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2
Symbol D BSC E BSC D2 E2 L K b e N ND
Min
Typ 3.00 3.00
A1
SIDE VIEW
Max
1.60 1.35 0.30 0 0.20 0.18
0.40
2.50 1.75 0.50 14 0.30
0.25 0.65 8 4
Notes 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2 1, 2, 5 1, 2 1, 2, 5
1. Figure 16 is shown for illustration only. 2. All dimensions are in millimeters; angles in degrees. 3. Dimensioning and tolerancing conform to ASME Y14.5 M-1994. 4. N is the total number of terminals. 5. The terminal #1 identifier and terminal numbering convention shall conform to JEDEC 95-1, SPP-012. Details of terminal #1 identifier are optional, but must be located within the zone indicated. The terminal #1 identifier may be either a mold or marked feature. 6. Dimension b applies to metallized terminal and is measured between 0.15mm and 0.30mm from the terminal tip. 7. ND refers to the maximum number of terminals on side D. 8. Unilateral coplanarity zone applies to the exposed heat sink slug as well as the terminals
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AS1337
Datasheet - O r d e r i n g I n f o r m a t i o n
11 Ordering Information
The device is available as the standard products listed in Table 5. Table 5. Ordering Information Ordering Code AS1337A-BTDT AS1337B-BTDT* *) on request Marking ASSE ASSF Descriptiom 200mA, DC-DC Step-Up Converter with Buck Mode; Battery Connect in Shutdown 200mA, DC-DC Step-Up Converter with Buck Mode; Battery Disconnect in Shutdown Delivery Form Tape and Reel Tape and Reel Package TDFN (3x3mm) 8-pin TDFN (3x3mm) 8-pin
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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AS1337
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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