ADP5350ACBZ-1-R7 datasheet(30/63 Pages) AD

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ADP5350

Data Sheet

Rev. B | Page 30 of 63

Figure 48 shows the typical boost regulator diagram in standalone

operation. Table 16 summarizes the difference between LED

operation mode and standalone operation mode. Table 16

provides four programmable OVP thresholds according to the

boost output voltage. The various OVP thresholds provide

different internal compensation depending on the boost output

voltage. It strongly recommended to select the proper OVP level

related to the set output voltage.

Figure 48. Boost Regulator in Standalone Operation Mode

Table 16. Two Operation Modes for the Boost Regulator

Operation

LED Operation

Mode

Standalone

Operation Mode

Activation

Control

Activated by active

LED EN_LEDx

Activated by EN_BST

Output

Regulation

Adaptive to LED VF

voltage variation

Fixed and determined

by external resistor

divider

FB4 Pin

Tied to ground

Tied to boost output

via resistor divider

OVP

5.6 V, 10 V, 15 V, or

18.5 V threshold on

the VOUT4 pin

5.6 V, 10 V, 15 V, or

18.5 V threshold on

the VOUT4 pin

PGOOD Indicator of Boost Output

In boost standalone mode, the PGOOD pin can be programmed

to indicate whether the boost PGOOD signal is output to the

external PGOOD pin by setting the PG4_BST_MASK bit high

in Register 0x37. The ADP5350 monitors the FB4 pin voltage,

and asserts the PGOOD signal high when the FB4 pin voltage

reaches up to 90% of the typical voltage with a typical 2 ms

deglitch time. The PGOOD signal asserts low when the FB4 pin

voltage drops to 86.5% of the typical voltage.

The boost output PGOOD status can be read via the I2C

interface, Register 0x36, Bit 1.

Soft Start

The boost regulator in the ADP5350 includes soft start circuitry

that ramps the output voltage in a controlled manner during

startup, thereby limiting the inrush current of the battery. The

soft start time is typically fixed at 1 ms for the boost regulator.

Backlight Current Settings

The backlight current setting is determined by a 6-bit code

programmed by the user via the IBL_SET[5:0] bits. This 6-bit

code allows the user to set the backlight to one of 64 levels

between 0 mA and 20 mA.

The ADP5350 uses a square law algorithm for the 64 levels,

where the backlight current increases linearly for a corresponding

increase of input code. The backlight current, in milliamperes

(mA), is determined by the following equations:

)

(













−

Current

Scale

Full

Code

Current

Backlight

where:

Code is the input code programmed by the user.

Full-Scale Current is the maximum sink current allowed

(typically, 20 mA).

Figure 49. Backlight Current vs. Sink Current Code

Backlight Linear Fade In and Fade Out

When the ADP5350 operates in normal operation, the backlight

can be turned on using the EN_BL bit. The backlight turns on

when EN_BL = 1, and turns off when EN_BL = 0.

To prevent abrupt turn on and turn off of the backlight, the

ADP5350 contains timers to facilitate smooth fading between

the turn on and turn off states. Fading is implemented using the

square law backlight code algorithm.

The BL_FI timer and BL_FO timer in the BL_FR register can be

used for smooth fade in transitions from a low to high backlight

setting. The BL_FI timer and BL_FO timer can be programmed

to one of 15 settings ranging from 0.3 sec to 4.5 sec. The timer

must be programmed before asserting EN_BL.

C10

10µF

ADP5350

VOUT4 (UP TO 16V)

AGND

RFB1

RFB2

PGND4

BOOST

REGULATOR

VISOS

4.7µH

4.7µF

LED DRIVER

OLED

(OR OTHER

LOAD)

FB4

VOUT4

SW4

SINK CURRENT CODE

ADP5350ACBZ-1-R7 Datenblatt(PDF) 30 Page - Analog Devices

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