ADP5350ACBZ-1-R7 datasheet(33/63 Pages) AD

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Data Sheet

ADP5350

Rev. B | Page 33 of 63

LED in Series

The ADP5350 supports connecting LEDs in series (see

Figure 54 for an example).

Figure 54. Four LEDs in Series (15 mA Each) for Grouped Backlight Connected

to D1, and One LED Strip or Indicator (2 mA) in D5 with Connection to VISOS Rail

Figure 54 shows four LEDs in series (15 mA each), in grouped

backlight configuration, connected to D1, and one additional

LED indicator (2 mA) connected to D5 and the VISOS rail.

Configure the boost regulator as follows:

Set BST_MODE = 0 to configure the boost in LED

operation mode.

Set BST_BL = 1 to configure the boost to provide the

bias voltage to the LED backlight only.

Set BST_OVP = 0 to configure the boost OVP

threshold = 18.5 V.

Configure the grouped backlight as follows:

Set IBL[5:0] = 15 mA for the LED backlight current.

Set the BL_FI and BL_FO code for the fade in and

fade out timer (if required).

Set FOVR = 1 to enable the fading overwritten feature

(if required).

Configure the individual current sink as follows:

Set ILED5 = 2 mA for D5 sink current.

Set the LED5_ON and LED5_OFF code for the

blinking timer (if required).

Set EN_BL = 1 to enable the LED backlight.

Set EN_LED5 = 1 to enable the LED indicator.

Boost Switching Frequency

The boost regulator of the ADP5350 operates in 1.5 MHz fixed

switching frequency and it is synchronized with the switching

frequency in battery charger.

Boost Current Limit

The boost regulator in the ADP5350 includes the peak current-

limit protection circuitry to limit the amount of positive current

flowing through the battery to the output. Two current-limit

thresholds (600 mA or 300 mA) can be selected using the

BST_IPK bit. The programmable current-limit threshold

feature allows the use of a small size inductor for low power

applications.

As the battery discharges, the lower battery voltage results in

higher peak current through the battery ESR, which may cause

early shutdown of other devices on the battery. The programmable

current threshold can be used to change the current limit

according to different battery voltages.

Overvoltage Fault

The boost regulator contains OVP circuits to prevent damage if

the VOUT4 voltage becomes excessive for any reason. To keep a

safe output level, the integrated OVP circuit monitors the VOUT4

voltage. When the VOUT4 voltage exceeds the OVP rising

threshold, the boost regulator stops switching, causing the

output voltage to drop. When the VOUT4 voltage goes lower than

the OVP falling threshold, the boot regulator begins switching,

causing the output to rise. The overvoltage threshold is

programmable (default of 18.5 V) in the BST_OVP register.

The overvoltage threshold level must be programmed according

to the output voltage because the various OVP thresholds

provide different internal compensation depending on the

boost output voltage.

LED Open-Circuit Protection

The LED circuit contains a headroom control circuit to minimize

power loss at each current source. Therefore, the minimum

feedback voltage is achieved by regulating the output voltage of

the boost regulator. If any LED string is opened during normal

operation, the current source headroom voltage is pulled to AGND.

In this condition, LED open-circuit protection activates when the

voltage on the Dx pin is less than 200 mV and the VOUT4 voltage

rises to the OVP level. If LED open-circuit protection is

triggered, the open LED channel turns off while the other LED

channel continues to work, and the LEDx_OPEN bit is set to 1

in the LED_STATUS register. The open LED channel remains

disabled to ensure protection against a potential LED open

circuit, until the processor clears the fault register by rewriting a

1 to the fault bit or the ADP5350 is power cycled.

When one channel is selected for independent LED operation

and the bias voltage is separate from the LED backlight group

(BST_BL = 1), the LED open-circuit protection has no effect on

this channel due to the boost OVP never being detected on this

channel.

LINEAR LOW DROPOUT (LDO) REGULATORS

The ADP5350 integrates three LDO regulators. LDO1 is a low

quiescent current LDO that can be used as a supply that is

always on for the system. LDO2 and LDO3 are general-purpose

LDO regulators.

All LDO input power rails are supplied from the VIN123 pin

and share the input power of the control circuits with the VIN4

pin. Thus, the VIN123 pin must be tied to the VIN4 pin in all

applications.

The LDO regulator operates with an input voltage range of

2.7 V to 5.5 V. The wide supply range makes the regulator

suitable for cascading configurations where the LDO supply

FB4

C10

4.7µF

ADP5350

VOUT4 (UP TO 17.5V)

AGND

PGND4

VOUT4

BOOST

VISOS

4.7µH

4.7µF

SW4

LED STRIP

OR INDICATOR

15mA

LED

DRIVER

VISOS

D2 D3 D4

2mA

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