AATIAN17 datasheet, PDF - EEWORLD Datasheet

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.

EV-125

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.

GND

EN

VCC

SCL

SDA

Slave

Master

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

I

2

C/S

2

Cwire™ Controller

with AAT1142 Demo Board

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.

EV-125

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 4.7kΩ 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.

2

EV-125.2006.08.1.1

I

2

C/S

2

Cwire™ Controller

with AAT1142 Demo Board

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.

EV-125

I

2

C and S

2

Cwire Switch

This switch changes the communication protocol between I

2

C and S

2

Cwire.

Button(s) Pushed

Up (SW1)

Down (SW2)

Description

[Push/Release once] Increment +50mV output voltage level.

[Holding 1.5 sec.+] Auto-increment one voltage level per second.

[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).

[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).

Reset (SW3)

Table 1: User Interface Functionality.

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-125.2006.08.1.1

3

I

2

C/S

2

Cwire™ Controller

with AAT1142 Demo Board

Schematic

DC+

R6

4.7K

J1

GND

EN

DC+

SCL

SDA

5

4

3

2

1

EV-125

GND

2

S1-B

1

3

4

S1-A

5

6

R7

4.7K

R8

4.7K

Header 5

GND

SCL

SDA

C3 (optional)

1pF

GND

C2 (optional)

1pF

GND

DC+

C1

1µF

U1

1

VDD

2

GP5

3

GP4

4

Fine/Coarse

Down

Up

0

2

4

0

2

4

0

2

4

SW3

1

3

5

R3

1K

R2

1K

R1

1K

GP3

VSS

7

GP0

6

GP1

5

GP2

R5

330

LED2

Green

8

R4

330

LED1

Red

PIC12F675

SW2

1

3

5

SW1

1

3

5

GND

Figure 2: I

2

C/S

2

Cwire Controller Board Schematic.

4

EV-125.2006.08.1.1

I

2

C/S

2

Cwire™ Controller

with AAT1142 Demo Board

Printed Circuit Board

EV-125

Figure 3: Top Layer (not to scale).

Figure 4: Bottom Layer (not to scale).

Bill of Materials

Component

U1

SW1 - SW3

R1, R2, R3

R4, R5

R6, R7, R8

C2, C3

C1

S1

LED1

LED2

J1

Part#

PIC12F675

PTS645TL50

Chip Resistor

VJ0603A1R0CXACW1BC

GRM216R61A105KA01

GT21MCBE

CMD15-21SRC/TR8

CMD15-21VGC/TR8

PRPN401PAEN

Description

8-bit CMOS, FLASH-based µC;

8-pin PDIP Package

Switch Tact, SPST, 5mm

1kΩ, 5%, 1/4W; 0805

330Ω, 5%, 1/4W; 0805

4.7kΩ, 5%, 1/4W; 0805

1pF, 50V, C0G, 0603

1µF, 10V, X5R, 0805

Toggle Switch, DPDT

Red LED; 1206

Green LED; 1206

Conn. Header, 2mm zip

Manufacturer

Microchip

ITT Industries

Vishay

MuRata

ITT Industries

Chicago Miniature Lamp

Sullins Electronics

Table 2: I

2

C/S

2

Cwire Controller Board Component Listing.

EV-125.2006.08.1.1

5

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