MP2681 – CC/CV CONTROLLER WITH FULL PROTECTION

MP2681 Rev.1.01

www.MonolithicPower.com

13

12/25/2013

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If the charger successfully goes through pre-

charge within the allowed time limit, it will start

CC charge and then CV charge. If the total

charge time exceeds T2 cycles and the battery

full has not been reached, the MP2681 will

terminate the charger and the CCON output will

be pulled high to turn off the switch and stop

charge. The timer out fault indication will also be

set: flashes LEDR and LEDG low. This function

prevents charging a dead battery for prolonged

duration. Table 2 shows the Timer for pre-charge

and total charge duration limit.

Table 2— Timer Cycles

Spec

T1

T2

Fast:115200

3S1P, 4S1P, 5S1P

57600

Slow:460800

Fast:172800

3S2P,4S2P,5S2P

86400

Slow:691200

The TMR pin is used to set the internal oscillator

frequency. The timer function can be disabled by

shorting TMR pin to ground although this is not

recommended.

The Timer frequency according to the TMR

capacitor is as below:

T(s)= 0.6×C(uF)

Smart Negative Temperature Coefficient

(NTC) Protection

The MP2681 continuously monitors the battery

temperature by measuring the voltage on the

NTC pin, which is generated by a negative

temperature coefficient (NTC) thermistor and an

external voltage divider. The controller compares

this voltage against its internal thresholds to

determine if the charging is allowed. As Figure 5

shows, to initiate a charge cycle, the voltage on

suspends charge and waits until the battery

slow charge mode, the charge current is set to

low and the NTC will not have any effect on the

charge current. Figure 5 shows the charge

current setting by the NTC window control.

Figure 5 — NTC control window

CCON

The CCON is a driver output pin used to turn

on/off the external MOSFET to connect or cutoff

the charge path according to the charge

condition. If the MP2681 is under normal charge

operation, the CCON is pulled low, else if a fault

happens, CCON is pulled high to cutoff the

charge path.

Status indication

The MP2681 integrates two driver outputs, LEDG

and LEDR. Connecting a bi-color back-to-back

LED between these two pins can output varieties

of indication states to help distinguish each

operation, including: charging, charge termination,

NTC fault, timer out, ID open, ID out pf range, ID

short and power line fault.

Table 3 below summarizes the status of the two

indication LEDs under the different charge state

based on the LEDR and LEDG outputs as Figure

6 shown.

Table 3- LED Indicator Table

Condition

Red

LED

Green

LED

CCON

Charging

OFF

Flash

Low

Charging

Finish/ID

short

OFF

ON

High

NTC Fault

Flash

OFF

High

Timer Fault/ID open/

ID out of range

Flash

OFF

High

Power Line Fault

Flash

OFF

High