VBG

200mV

CTRL

Error

Amplifer

FB

TPS61165

SLVS790A – NOVEMBER 2007 – REVISED MAY 2010

www.ti.com

For optimum performance, use the PWM dimming frequency in the range of 5kHz to 100kHz. The requirement of

minimum dimming frequency comes from the EasyScale detection delay and detection time specification in the

dimming mode selection. Since the CTRL pin is logic only pin, adding external RC filter applied to the pin does

not work.

To use lower PWM dimming, add external RC network connected to the FB pin as shown in the additional typical

application, Figure 17.

Figure 13. Block Diagram of Programmable FB Voltage Using PWM Signal

DIGITAL 1 WIRE BRIGHTNESS DIMMING

The CTRL pin features a simple digital interface to allow digital brightness control. The digital dimming can save

the processor power and battery life as it does not require a PWM signal all the time, and the processor can

enter idle mode if available.

The TPS61165 adopts the EasyScale™ protocol for the digital dimming, which can program the FB voltage to

any of the 32 steps with single command. The step increment increases with the voltage to produce pseudo

logarithmic curve for the brightness step. See Table 1 for the FB pin voltage steps. The default step is full scale

register. A power reset clears the register value and reset it to default.

EasyScale™: 1 WIRE DIGITAL DIMMING

EasyScale is a simple but flexible one pin interface to configure the FB voltage. The interface is based on a

master-slave structure, where the master is typically a microcontroller or application processor. Figure 14 and

Table 2 give an overview of the protocol. The protocol consists of a device specific address byte and a data byte.

The device specific address byte is fixed to 72 hex. The data byte consists of five bits for information, two

address bits, and the RFA bit. The RFA bit set to high indicates the Request for Acknowledge condition. The

Acknowledge condition is only applied if the protocol was received correctly. The advantage of EasyScale

compared with other on pin interfaces is that its bit detection is in a large extent independent from the bit

transmission rate. It can automatically detect bit rates between 1.7kBit/sec and up to 160kBit/sec.

Table 1. Selectable FB Voltage

FB voltage

D4

D3

D2

D1

D0

(mV)

0

0

0

0

0

0

0

1

5

0

0

0

0

1

2

8

0

0

0

1

0

3

11

0

0

0

1

1

4

14

0

0

1

0

0

5

17

0

0

1

0

1

6

20

0

0

1

1

0

7

23

0

0

1

1

1

8

26

0

1

0

0

0

10

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