MP2615C

– 2.1A, 1-CELL OR 2-CELL LI-ION BATTERY CHARGER

MP2615C Rev. 1.1

www.MonolithicPower.com

13

6/15/2023

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2023 MPS. All Rights Reserved.

OPERATION

The MP2615C is a peak current mode control

switching charger for single-cell or dual-cell Li-ion

and

Li-polymer

batteries.

The

MP2615C

integrates

both

the

high-side

and

low-side

MOSFETs of the synchronous buck converter to

provide high efficiency and reduce PCB size.

Charge Cycle (Mode Change: TC to CC to CV)

The MP2615C regulates the charge current (ICHG)

and battery voltage (VBATT) using two control

loops to achieve highly accurate constant current

(CC) charge and constant voltage (CV) charge.

If VBATT is below VTC, the MP2615C remains in

trickle charge mode, and the output of the charge

current loop (COMPI) dominates the control (see

Figure 2). The battery is charged by a trickle

charge current (ITC) until the battery voltage

reaches VTC. If the charger remains in trickle

charge mode until the trickle charge timer is

triggered, charging is terminated.

The MP2615C enters CC charge mode once the

battery voltage exceeds VTC. In this mode, the

charge current increases from ITC to ICC to fast

charge the battery.

If the battery voltage exceeds the battery-full

voltage (VBATT_FULL), the charger enters CV mode.

In CV mode, the battery voltage is regulated at

VBATT_FULL, and the charge current falls naturally

due to the existing equivalent internal resistance

of the battery. Figure 4 shows an operation

flowchart.

CC Charge

Threshold

CV Charge

Threshold

CC

Charge

ICHG

VBATT

Charge

Full

TC Charge

Current

CC Charge

Current

CV

Charge

Auto-

Recharge

Auto-

Recharge

Threshold

IBF

Trickle

Charge

Figure 2: Li-Ion Battery Charge Profile

Charge Full Termination and Auto-Recharge

If

the

charge

current

drops

below

the

termination threshold (IBF) during the CV charge

phase, the charger stops charging and the

CHGOK

pin becomes an open drain. The timer

resets and turns off. Once the battery voltage

drops below the recharge threshold (VRECH)

(4.0V/cell while the SEL pin is connected to

AGND), recharging automatically begins and

the timer restarts a new charge cycle.

Constant-Off-Time (COT) Charge Mode

The MP2615C uses the floating ground method

to drive the

buck converter’s high-side MOSFET

(HS-FET). While the HS-FET is off, the BST

capacitor is recharged, and the voltage across

the capacitor is used as the HS-

FET’s gate

driver. Thus a minimum off time of 200ns is

required to maintain sufficient voltage at the

BST capacitor.

When the 200ns minimum off time is achieved

due to a large duty cycle, the MP2615C enters

constant-off-time (COT) charge mode. In this

mode,

the

switching

frequency

is

slightly

reduced to achieve a 99% duty cycle.

Charge Status Indication

The MP2615C has two open-drain status

outputs: the CHGOK and ACOK pins. The

ACOK pin goes low when the input voltage

exceeds the battery voltage and the under-

voltage lockout (UVLO) threshold by 300mV.

The CHGOK pin indicates the status of the

charge cycle.

Table 1 lists the operation for both CHGOK and