ev-125 i 2 c/s 2 cwire? controller with aat1142 demo board introduction this document describes how to connect the i 2 c/s 2 cwire controller board to the aat1142 dynamically program- mable dc/dc buck converter. the schematic and pcb drawing of the controller board, as well as the function of each button, is described. the i 2 c/s 2 cwire controller board contains a microcontroller which provides the i 2 c and s 2 cwire interface via a five-wire ribbon cable. this controller board works as a master device in either the i 2 c or s 2 cwire system, while the aat1142 slave device receives data and varies the aat1142 output voltage in response to push-button commands. the microcontroller is programmed with one i 2 c slave address. getting started figure 1 shows how to connect the i 2 c/s 2 cwire controller board to the aat1142 demo board. esd protection (ground cable) is recommended to prevent unwanted esd events. figure 1: connection of aat1142 demo board and i 2 c/s 2 cwire controller board. there are three (3) buttons on the controller board. selecting the 'up' or 'down' button blinks the green led, indicating that the i 2 c or s 2 cwire signal was successfully transmitted from the microcontroller. the output volt- age level of the aat1142 responds by adjusting the aat1142 demo board output voltage in 50mv incre- ments. by holding the 'up' or 'down' button, the voltage level is auto-incremented and auto-decremented with- in the aat1142 specified operating voltage range (please refer to the aat1142 datasheet). selecting the 'up' or 'down' button at the voltage extremes returns the output to the lowest or highest voltage level, respective- ly. the 'reset' button sets the output voltage level to the lowest setting. there is a toggle switch on the controller board that switches between the i 2 c and s 2 cwire communication pro- tocols. when the switch is in the left position, the s 2 cwire protocol is implemented via the en pin. when the switch is in the right position, the i 2 c protocol is implemented via the scl and sda pins. it can be switched at any time, as the microcontroller has auto-detection capability. upon initial power-up and prior to i 2 c or s 2 cwire programming, the default output voltage of the aat1142 is set at 1.8v. the input dc voltage range of the i 2 c/s 2 cwire controller board and aat1142 demo board is 2.7v to 5.5v. on/off control of the aat1142 demo board using i 2 c interface is accomplished by applying or remov- ing dc input voltage. ev-125.2006.08.1.1 1 slave gnd en vcc scl sda master
pinouts connection the five-wire ribbon cable connector is a standard 0.1-inch (2.54mm) pitch. one end has a five-header con- nector and the other end has two connectors (three-header and two-header). the five-header connector should connect to the controller board. the three-header and two-header are connected to the aat1142 demo board in the orientation shown in figure 1. order of leads 1. gnd 2. en 3. vcc 4. scl 5. sda ground pin it is imperative that the controller board be on a common ground with the slave board. if the ground is not con- nected, the signaling is entirely unpredictable and communication will likely be corrupted. vcc pin vcc is the power for the master system and the voltage range is from 2.7v to 5.5v. the dc source powers both the i 2 c/s 2 cwire controller board and aat1142 demo board. i 2 c pins scl (serial clock line): the signal used to synchronize communication between the master and the slave. sda (serial data line): the signal used to transfer data between the transmitter and the receiver. en pin en (en/set): when using the i 2 c protocol interface, this en pin provides logic high to enable the demo board device. when using the s 2 cwire protocol interface, the demo board provides clock edges. (please refer to the aat1142 product datasheet for more information.) pull-up resistors there is a 4.7k resistor on each i 2 c line (scl, sda) and s 2 cwire enable (en) pins. these pins are effec- tively pulled up to the v cc input rail, resulting in approximately 1ma of pull-up current. the i 2 c specification allows for a maximum of 3ma pull-up current on each i 2 c line. ev-125 i 2 c/s 2 cwire? controller with aat1142 demo board 2 ev-125.2006.08.1.1
external power source this controller board can be powered either from the aat1142 demo board through the ribbon cable 1 or from a separate power supply. to use a separate external power source, simply disconnect the vcc pin from the controller board, then connect an external power supply to the power post. the input voltage of the controller board can be in the range of 2.5v to 5.5v. for detailed information regarding the v il or v ih level of the i 2 c bus, please read the i 2 c specification or refer to the electrical characteristic table in the aat1142 product datasheet. i 2 c and s 2 cwire switch this switch changes the communication protocol between i 2 c and s 2 cwire. table 1: user interface functionality. button(s) pushed description up (sw1) [push/release once] increment +50mv output voltage level. [holding 1.5 sec.+] auto-increment one voltage level per second. down (sw2) [push/release once] decrement -50mv output voltage level. [holding 1.5 sec.+] auto-decrement one voltage level per second. [push/release once at i 2 c mode] set to the lowest voltage level (0.6v). reset (sw3) [push/release once at s 2 cwire mode] set to the lowest voltage level of s 2 cwire (0.65v). [holding 1.5 sec. at s 2 cwire mode] disables output, disabling dc output 2 (0v), and then return to lowest voltage level of s 2 cwire (0.65v). ev-125 i 2 c/s 2 cwire? controller with aat1142 demo board ev-125.2006.08.1.1 3 1. when using the common power source, r3 on the aat1142 demo board must be shorted. 2. on/off control using the i 2 c interface is accomplished by applying or removing the dc input voltage.
ev-125 i 2 c/s 2 cwire? controller with aat1142 demo board 4 ev-125.2006.08.1.1 schematic figure 2: i 2 c/s 2 cwire controller board schematic. vdd 1 gp5 2 gp4 3 gp3 4 gp2 5 gp1 6 gp0 7 vss 8 u1 1f c1 1k r1 1k r2 1k r3 330 r4 1 2 3 4 5 0 sw1 1 2 3 4 5 0 sw2 led1 red led2 green 1 2 3 4 5 0 sw3 gnd dc+ 330 r5 sda scl gnd gnd gnd gnd gnd 2 1 3 5 4 6 1 2 3 4 5 header 5 j1 dc+ s1-b s1-a 4.7k r6 4.7k r7 4.7k r8 1pf c3 (optional) 1pf c2 (optional) fine/coarse down up gnd en dc+ scl sda pic12f675
printed circuit board figure 3: top layer (not to scale). figure 4: bottom layer (not to scale). bill of materials table 2: i 2 c/s 2 cwire controller board component listing. component part# description manufacturer u1 pic12f675 8-bit cmos, flash-based c; microchip 8-pin pdip package sw1 - sw3 pts645tl50 switch tact, spst, 5mm itt industries r1, r2, r3 chip resistor 1k , 5%, 1/4w; 0805 vishay r4, r5 chip resistor 330 , 5%, 1/4w; 0805 vishay r6, r7, r8 chip resistor 4.7k , 5%, 1/4w; 0805 vishay c2, c3 vj0603a1r0cxacw1bc 1pf, 50v, c0g, 0603 vishay c1 grm216r61a105ka01 1f, 10v, x5r, 0805 murata s1 gt21mcbe toggle switch, dpdt itt industries led1 cmd15-21src/tr8 red led; 1206 chicago miniature lamp led2 cmd15-21vgc/tr8 green led; 1206 chicago miniature lamp j1 prpn401paen conn. header, 2mm zip sullins electronics ev-125 i 2 c/s 2 cwire? controller with aat1142 demo board ev-125.2006.08.1.1 5
ev-125 i 2 c/s 2 cwire? controller with aat1142 demo board 6 ev-125.2006.08.1.1 advanced analogic technologies, inc. 830 e. arques avenue, sunnyvale, ca 94085 phone (408) 737-4600 fax (408) 737-4611 ? advanced analogic technologies, inc. analogictech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an analogictech pr oduct. no circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. analogictech reserves the right to make changes to their products or specifi cations or to discontinue any product or service without notice. customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information b eing relied on is current and complete. all products are sold sub- ject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. analogictech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with anal ogictech?s standard warranty. testing and other quality con- trol techniques are utilized to the extent analogictech deems necessary to support this warranty. specific testing of all param eters of each device is not necessarily performed. analogictech and the analogictech logo are trademarks of advanced analogic technologies incorporated. all other brand and produ ct names appearing in this document are regis- tered trademarks or trademarks of their respective holders.
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