AS1326 - Evaluation Board Application Note AS1326 Evaluation Board Application Note www.austriamicrosystems.com Revision 1.00 1-5 AS1326 - Evaluation Board Application Note General Description Board Description Figure 2: Board Description Figure 1: Board Description Connector Description Label Name A A:ONN B:ON VREF B C CLK/SEL D E F VOUT VIN GND Description Info Enable Input AS1326A: 0=ON, 1=OFF AS1326B: 0=OFF, 1=ON Internal Reference Bypass Pin 0: Normal operation enabling automatic powersave mode 1: Forced PWM-mode Clocked: Forced PWM-mode with the internal oscillator synchronized to this pin between 500kHz and 1.2MHz. Power Output Connector Input Voltage Ground Input voltage ranging from 0.7V to 5V Jumper Description Label Name Description G A:OFF/ON B:ON/OFF Enable Jumper H LOW/HIGH Mode Selection Info AS1326A: AS1326B: ON OFF ON OFF LOW Normal Operation Mode HIGH Forced PWM Mode Measurement Points Description Label Name Description I J L M GND VIN LX OUT Power Supply Connectors for VBATT and Ground. External Conductor Power Output Connector Info Additional Components Label Name Description Info N O P RSS2 CSS R1 Current Limit Resistance Softstart Capacitance Output Voltage Resistance ILIMIT=1.6A*RSS2/(RSS+RSS2) tSS=(RSS*RSS2/(RSS+RSS2))CSS R1=R2*(VOUT/VFB-1) www.austriamicrosystems.com Revision 1.00 2-5 AS1326 - Evaluation Board Application Note Operational sequence This evaluation board comes with the AS1326A. The output voltage is set to the default 3.3V but can be adjusted if an additionally resistor R1 “P” is soldered on the board. 1. If not present get the datasheet for the AS1326 from www.austriamicrosystems.com. Drive the IC on the Demoboard only with the recommended settings and values as described in the datasheet. 2. Connect a +0.7V to VOUT power supply (VIN “E” and GND “F”). 3. Perform measurements at the measurement points “I” to “M”. If there are questions do not hesitate to contact us. See contact information at the end of the application note. Optional Features Setting the output voltage The AS1326 has a default output voltage of 3.3V. Additionally the output voltage can be set between 2.5 and 5V via an additionally resistor R1 which can be placed at “P”. The required resistor value for a certain output voltage can be calculated as shown in equation 1. R1=R2*(VOUT/VFB-1) (Eq1) R1=270kΩ*(VOUT/1.24V-1) (Eq2) Using the current limiter The ISET pin is used to adjust the inductor current limit and to implement the soft-start feature. With pin ISET connected to pin REF, the inductor current limit is set to 1.6A. With ISET connected to a resistor-divider network from pin REF to GND, the current limit is calculated as: ILIMIT=1.6A*RSS2/(RSS+RSS2) (Eq3) ILIMIT=1.6A*RSS2/(220kΩ+RSS2) (Eq4) Setting the soft-start On default the soft-start feature is disabled. The soft-start feature can be implemented by placing a resistor RSS (already soldered) between pin ISET and pin REF and a capacitor CSS between pin ISET and GND. At power-up, ISET is 0V and the LX current is tSS=RSS*CSS (Eq5) tSS=220kΩ*CSS (Eq6) If the current limiter resistance is also in use, the equation for the soft-start time would be: tSS=(RSS*RSS2/(RSS+RSS2))CSS (Eq7) tSS=(220kΩ*RSS2/(220kΩ+RSS2))CSS (Eq8) www.austriamicrosystems.com Revision 1.00 3-5 AS1326 - Evaluation Board Application Note Layout of evaluation board Board schematics and layout Figure 3: Schematics Figure 4: Top view Figure 5: Bottom view Assembly List Label CIN COUT or L1 RSS R1 RCC CRC RCC Info 33µF, ±10%, 10V, 150mΩ 100µF , ±10%, 10V, 50mΩ 82µF , ±20%, 6.3V, 18mΩ 3.3µH, 46mΩ, 1.8A 220kΩ 270kΩ 10Ω 330nF 10nF www.austriamicrosystems.com Type TPSC336K010R0150 T495D107M010ATE050 A700V826M006ATE018 MOS6020-332 Revision 1.00 Manufacturer AVX Kemet Kemet Coilcraft 4-5 AS1326 - Evaluation Board Application Note Copyright Copyright © 1997-2007, austriamicrosystems AG, Schloss Premstaetten, 8141 Unterpremstaetten, AustriaEurope. Trademarks Registered ®. All rights reserved. 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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 A-8141 Schloss Premstätten, Austria T. +43 (0) 3136 500 0 F. +43 (0) 3136 5692 For Sales Offices, Distributors and Representatives, please visit: http://www.austriamicrosystems.com/contact www.austriamicrosystems.com Revision 1.00 5-5