12

ICS1700A

Voltage Reference: VREF Pin

A 1.26V reference is present at this pin. The reference sets internal

voltage references such as the 0.5V and 2.0V internal thresholds

used by the controller for battery polling/fault detection and the

analog/digital converter range.

The reference provides a fast way of checking the internal

thresholds. Measuring VREF with a high input impedance volt

meter (>1M

buffered with a high impedance device having an input impedance

greater than 1M

voltage

thresholds

and

analog/digital

converter

range

and

resolution are not altered.

The reference may be overridden by an external 1.2V to 1.3V

reference.

Power: VDD Pin

The power supply for the device must be connected to the VDD

pin. The voltage should be +5 VDC and should be supplied to the

part through a regulator that has good noise rejection and an

adequate current rating. The controller requires up to a maximum

of 11mA with V

DD

=5.00V.

Grounding: VSS, AVSS Pins

There are two ground pins. Both pins must be connected together

at the device. This point must have a direct connection to a solid

ground plane.

If a temperature sensor is not used, the THERM pin must be

grounded.

Voltage Input: VIN Pin

The battery voltage must be normalized by an external resistor

divider network to one cell. The electrochemical potential of one

cell is about 1.2V. For example, if the battery consists of six cells

in series, the voltage at the VIN pin must be equal to the total

battery voltage divided by six. This can be accomplished with two

resistors, as shown in Figure 11. To determine the correct resistor

values, count the number of cells to be charged in series. Then

choose either R1 or R2 and solve for the other resistor using:

R1 = R2 * (# of cells -1) or R2 =

R1

(# of cells -1)

Figure 11: Resistor divider network

at the VIN pin

R1

R2

VIN pin

# of cells