DA9155M datasheet(21/36 Pages) DIALOG

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DA9155M

2.5 A Companion Charger for rapid charging

frequency fold back mode, where the switching frequency is stepwise reduced until a required duty

cycle can be achieved. Without the frequency fold back the duty cycle is limited by the Buck’s

minimum off-time.

It is recommended to configure the switching frequency to 1 MHz when operating with 5 V VIN.

10.4

Safety timer

DA9155M features a safety timer that is intended to disable the Buck converter in the event of

system malfunction during charging.

Whenever the Buck is enabled, either through the EN pin or from a register, the safety timer is

loaded with a pre-programmed value (TIMER_LOAD) and it starts decrementing. In normal operation

the application processor should periodically re-initialize the safety timer by writing a new value to the

TIMER_LOAD register. The value of the counter can be read from the TIMER_COUNT register.

However, if the timer reaches zero an event is asserted, and the Buck is automatically disabled. The

BUCK_EN register is cleared and the Buck is stopped by ramping down the output current at a rate

defined in SLEW_RATE. Resuming normal operation requires that the event is cleared.

10.5 VIN monitoring

VIN is monitored to detect a power supply insertion, and to ensure that VIN is within an acceptable

voltage range. The monitoring is illustrated in .

When VIN is below the VIN2BAT threshold DA9155M stays in the no-power mode. When VIN rises

above the VIN2BAT threshold, DA9155M moves to the reset mode where the internal supply and

reference are enabled.

VIN

VBAT

VIN_UV

IN2BAT

VBAT_OV

VBAT_UV

VREF

VIN_OV

VIN_DROP

Figure 18: VIN monitoring of DA9155M

In reset, disabled, and active mode, VIN is monitored against over- and undervoltage. If over- or

undervoltage is detected, an event is triggered (E_VIN_OV, E_VIN_UV), the BUCK_EN register is

cleared, and DA9155M moves to disabled mode. Re-enabling the Buck requires that the status and

event bits are cleared.

During charging VIN is monitored for weak charger or high impedance USB cable detection. If VIN

drops below the threshold VIN_DROP, an event is triggered (E_VIN_DROP) and the Buck is

automatically disabled. The BUCK_EN register is cleared and the Buck is stopped by ramping down

the output current at a rate defined in DEF_SLEW_RATE. The Buck does not start automatically

when the VIN rises above the threshold. Resuming normal operation requires that the status and

event bits are cleared. This feature is targeted for use cases where the VIN is above the standard

Datasheet

v3.05

22-July-2016

CFR0011-120-00 Rev 5

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