MP2681B – CC/CV CONTROLLER WITH FULL PROTECTION

MP2681B Rev.1.0

www.MonolithicPower.com

12

12/22/2014

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Table 1 summarizes all the charge-voltage

settings for the MP2681B. The real ID voltage

threshold for every battery pack is about ±65mV

wider than the ones listed in the table, taking into

consideration reference variations, comparator

offsets, and hysteresis.

Table1. Charge-Voltage Setting Summary

ID Resistor

Detect Voltage

Operation

Mode

Battery Spec

VDD

VBATT

Float

NTC Float

Sleep Mode

No Battery

10.8V

0

NTC OK

Default Mode

3S

12.44V

12.44V

1.8k

Automatic Mode

3S

12.44V

12.44V

6.8k

4S

16.59V

16.59V

15k

5S

20.74V

20.74V

Short

Sleep Mode

Unknown

10.8V

0

ID voltage is detected out of range based on the

values specified in Table 1 (possibly caused by

the

insertion

of

a

wrong

battery-pack

configuration). The MP2681B detects this fault

condition and cuts off the external MOSFET to

stop charging and protect the battery. Under this

condition, the output voltage is set to a default

value of 10.8V, causing the MP2681B to enter

sleep mode. Also, the MP2681B provides a fault

indication. No battery condition is detected when

both NTC and ID are floating; when there is no

battery, the indication is off. If the NTC is ok

(while ID is floating), it means the battery has no

ID resistor, and the MP2681B will default set it as

a 3 cell condition.

The MP2681B compares the VFB voltage to its

internal voltage reference in order to maintain

voltage regulation. If this voltage is higher than

2.075V, the output of the voltage-loop operational

amplifier decreases; the opto-coupler current will

increase, reducing the output voltage of the PWM

controller.

Figure 3 shows the CC and CV control circuit.

Figure 3. CC/CV Control Circuit of MP2681B