Board schematics

AN2818

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8.2

Controlling/changing the charging parameters

Table 4 provides methods to configure various NiMH battery-charging parameters.

Table 4.

NiMH parameter configuration

Signal

no.

Parameter

name

Function

Formulae

Comments

1

NiMH_VF_H

To define constant

voltage threshold or to fix

the constant voltage level

X = [(Threshold / {2 * 3.6})] *

1024

Example:

X = 597 for 4.2 V threshold

2

NiMH _VFAST

Voltage to switch from

pre-charge level

X = [(Threshold / {2 * 3.6})] *

1024

Example:

X = 469 for 3.3 V pre-charge

threshold

3

NiMH _VFAIL

Not used

4

NiMH _VF_L

Not used

5

NiMH _VSC

Used along with

LION_TFAIL to define

bad battery condition

X = [(Threshold / {2* 3.6})] *

1024

Example:

X = 213 for 1.5 V threshold

6

NiMH _VSAT

Voltage to switch from

pre-charge level

X = [(Threshold / {2 * 3.6})] *

1024

Example:

X = 469 for 3.3 V pre-charge

threshold

7

NiMH

_ICONST

Current level during

constant current charging

Y = Current_Thre / 2.5

Example:

Y = 120 for 300 mA charging

current

8

NiMH _ITRI_1

Constant current level

during pre – charging

phase

Y = Current_Thre / 2.5

Example:

Y = 20 for 50 mA pre -

charging current

9

NiMH _ITRI_2

Not used

10

NiMH _IFAIL

Short circuit current

threshold

Y = Current_Thre / 2.5

Example:

Y = 140 for 350 mA short

circuit current

11

NiMH _ISAT

Current threshold to end

the charging

Y = Current_Thre / 2.5

Example:

Y = 18 for 45 mA short circuit

current

12

NiMH

_VHEAT_UP

Heat condition indicator

threshold

Z = {R1 / (10 k

Ω + R1)} * 256

Example:

Z = 80 for 45 deg temperature

(here R1 is in k

Ω)

13

NiMH

_VHEAT_DO

WN

Cold condition indicator

threshold

Z = {R1 / (10 k

Ω +

R1)} * 256

Example:

Z = 195 for 0 deg temperature

(Here R1 is in k

Ω)

14

NiMH _TFAIL

Used with LION_VSC

15

NiMH _TEXP

Expiry condition in

minutes

W = (expected time expiry

value in minutes) / 2

Example:

W = 150 for a 5 hour time

expiry condition