Vaux

TS M102 Vref

Vcc

+

9

Vaux

13

8

+

Figure 3 : A precise power supply for the TSM102A and other components

= 2.5 / [ 56 / (131.5 + 56 + 0.68 ) ]

= 8.400V

Vout = 8.400V

Low Battery signal :

If R5 = 0

Ω and R6 = open :

Vout(LoBatt) = Vref / [ R19 / ( R17 + R19 ) ]

= 2.5 / [ 10 / (12.4 + 10) ]

= 5.6V

Vout(LoBatt) = 5.6V

End of Charge signal :

Vout(EOC)

= Vref / [ (R2 + R3 ) / (R1 + R2 + R3) ]

= 2.5 / [ (56 + 0.68) / (131.5 + 56 + 0.68) ]

= 8.300V

Vout (EOC)= 8.300V

Notes:

The current control values must be chosen in ac-

cordance with the elements of the primary side. The

performances of the battery charger in their global-

ity are highly dependent on the adequation of the

primary and the secondary elements.

The addition of the diode D9 is necessary to avoid

dramatic discharge of the battery cells in case of

the charger disconnection from the mains voltage,

and therefore, the voltage measurement is to be

operated on the cathode side of the diode not to

take its voltage drop into account. The total bridge

value of R1, R2, R3 must ensure low battery dis-

charge if the charger is disconnected from main,

but remains connected to the battery by mistake.

The chosen values impose a 44

µA discharge cur-

rent max.

R12 and R13 are the equivalent resistors seen from

the opamp and from the comparator.

A hysteresis resistor can be connected to the ”End

Of Charge” comparator to ensureproper hysteresis

to this signal, but this resistor must be chosen

carefully not to degrade the output voltage preci-

sion. It might be needed to impose unidirectionnal

hysteresis (by inserting a diode on the positive

feedback of the comparator).

Figure 3 shows how to use the integrated Voltage

Reference to build a precise Power Supply for the

TSM102

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