PCA9420 datasheet(23/87 Pages) NXP

23 / 87 page

NXP Semiconductors

PCA9420

Power management IC for low-power microcontroller applications

For more details, see Figure 10.

8.12.4 Low-battery/dead-battery (pre-qualification) charging

If the battery is detected and VBAT < VBAT_LOW, the charger initiates pre-charging

using a predefined (I2C register) current.

When it is under the dead-battery condition, the charging current ICHG_DEAD is

programmed by ICHG_DEAD [5:0]; and when it is under the low-battery condition, the

charging current ICHG_LOW is programmed by ICHG_LOW [5:0]. When VBAT ≥ VBAT_LOW,

the charger moves to the next state, fast charging mode.

8.12.5 Constant current charging/constant voltage charging (fast charging) and

termination

When VBAT ≥ VBAT_LOW, the charger enters Fast Charge Mode (Constant Current). In this

state, the battery voltage VBAT continues to rise, while the battery is being charged with

the current set by ICHG_CC [5:0], until VBAT reaches the maximum allowable voltage

set by VBAT_REG [5:0].

At this time, the charger enters the Constant Voltage (CV) mode. While operating in

the CV mode, the voltage is still regulated at the level set by VBAT_REG [5:0], and the

charging current continues to decrease.

When the charging current drops below the top-off current threshold, set by

ICHG_TOPOFF [5:0], the charger enters TOPOFF mode, and upon expiration of

TOPOFF timer (set by T_TOPOFF [1:0]), the charger enters DONE mode.

8.12.6 Charger safety timers

Two sets of charging safety timers are implemented on PCA9420. These timers

ensure the charging is terminated if the charging time is longer than its predefined limit

(programmed via I2C registers) at given states:

• Pre-qualification timer, set by ICHG_PREQ_TIMER [1:0], 15 min to 60 min

• Fast charge timer, set by ICHG_FAST_TIMER [1:0], 3 hr to 9 hr

8.12.7 Recharging

While in DONE mode, if the voltage of VBAT stays below (a programmed VBAT_REG –

140 mV or 240 mV) over the deglitch time (tDGL_BAT_RESTART), 50 ms the battery charger

resumes back to Constant Current (CC) Mode.

8.12.8 Starting a new charge cycle

When a VIN plug in, VBAT attached, or CHG_EN are set to “1”, the device initializes a

new charging process.

8.13 Hardware and software reset

Please refer to description for ON pin for the hardware reset function by a long time

ON key pressed. The "software reset” is achieved by setting “1” to SW_RST bit in I2C

setting; this bit is cleared and reset back to “0” as well.

PCA9420

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 4.0 — 28 November 2022

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