# Battery Charging Regulator Schematic Circuit Diagram

#### Philips IC TEA1100: Fast and Efficient Battery Charging

The Philips IC Type TEA1100 employs the delta-peak principle to achieve rapid and effective charging of nickel-cadmium (NiCd) and nickel-metal-hydride (NiMH) batteries. The primary function of the delta-peak battery charging regulator is to monitor and assess changes in the battery voltage. Charging is halted if the voltage at pin 7 drops 1% or more below the average maximum. As per the manufacturers’ data sheet, the voltage at pin 7 should ideally be within the range of 0.385–3.85 V. The potential divider R4-R5 is instrumental in ensuring that the battery electromotive force aligns with this specified range.

The values of these resistors are given by:

• R4/(R4+R5).n.-1.8 <3.85:
• R4/(R4+R5) < 2.14n;
• R4/(R4+R5).n.1.1 >0.385;
• R4/(R4+R5) >0.35n.

The charging current 4 is given by:

• IC = 1•25Rsense/Rshunt’Rref.

Where Rsense is R10; Rshunt is R8 parallel with R9; and Rref is R2. Timeout (TO) is a safety facility of the IC. If, for whatever reason, no maximum can be detected, the IC stops charging after the timeout. This time constant is given by:

TO = 226.0.93.RrefCosc,

where Cosc = C3. Note that both timeout and charging current are influenced by R2. When the charging current and timeout 0 are being determined, the value of R2 must, therefore, be fixed and that of C3 must be variable.

#### TEA1100’s ‘Maintain Charge’ Mode for Fully Charged Batteries

Upon reaching full charge, the TEA1100 transitions into the ‘maintain charge’ mode. In this state, during 1/10 of the regular charging time, only 1/2 of the standard charging current is active. Essentially, the battery undergoes a trickle charge at 1/20 of the normal charging current. The formula I_trickle = I * 2.5 * R_sense / (1 + R_shunt / R_N) determines the trickle-charge current, where the current is influenced by the shunt resistor’s voltage drop and controlled by transistors through pin 2 of the IC. The stability of the circuit is maintained through the presence of capacitor C2.

#### Battery Connection and LED Indicators

When K1 has no connected battery or when a battery is undergoing trickle charging, the LED DI flashes. If the voltage at pin 7 drops, the LED lights continuously. The supply voltage at pin 12 must fall within the range of 5.65–11.5 V. The quiescent current, when all outputs are off, is approximately 4 mA. The TEA1100 IC extends its utility to various applications, with additional details provided in Philips’ Data Sheets TEA1100 and TEA1100T.

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