7

ICS1700A

Battery Fault Detection

The ICS1700A will turn on the PFN fault indicator and shut down

if the battery is removed or if an open circuit occurs in the current

path anytime after fast charge has been initiated. When in the

topping charge or maintenance charge stages, a charge pulse may

not occur for several seconds. During the period between charge

pulses, the voltage at VIN should be greater than 0.5V if a battery

is attached. If the voltage at VIN is less than 0.5V, the ICS1700A

assumes the battery has been removed, a fault condition is

indicated by the PFN fault indicator, and the controller shuts down.

Cold Battery Charging

Cold battery charging is activated if a voltage at the THERM pin is

in the cold battery voltage range, as shown in Figure 7. The

ICS1700A checks for a cold battery before initiating fast charge. If

a cold battery is present before fast charging begins, the ICS1700A

begins a two-hour C/10 topping charge (the pulsed duty cycle is

based on the selected charge rate). If the battery is still cold after

the two-hour topping charge is complete, the ICS1700A begins a

C/40 maintenance charge. The maintenance charge will continue

for as long as the battery remains cold. The thermistor voltage at

the THERM pin is checked every second to see if the battery has

warmed up. If so, the ICS1700A stops the topping charge or

maintenance charge and begins a fast charge at a rate selected by

the SEL0 and SEL1 inputs. See the section on Temperature

Sensing for more information.

The CMN will flash at a one-second rate, and the OTN indicator

will be active, indicating that a low current charge is being applied

to a battery that is outside the specified temperature range for fast

charging.

Battery Polling

Upon power-up or after a reset is issued, any excess charge from

filter capacitors at the charging system terminals is removed with a

series of discharge pulses. After the discharge pulse series is

complete, the voltage at VIN must be greater than 0.5V when a

battery is present. If the voltage at VIN is less than 0.5V, the

ICS1700A assumes no battery is attached and initiates a polling

sequence.

The ICS1700A then applies a 100ms charge pulse. During the

pulse, the ICS1700A monitors the VIN pin to determine if the

divided down terminal voltage is greater than the internal 2.0V

reference. If the battery is present, the voltage is clamped below the

2.0V reference when the current pulse is applied and the fast

charge stage begins immediately. If a battery is not present, the

voltage at VIN rises above the 2.0V reference and the PFN fault

indicator is activated.

The charge pulses repeat for 10 seconds. If the battery is installed

within 10 seconds, the ICS1700A will turn off the PFN fault

indicator and enter the soft start stage. If the battery is not installed

within 10 seconds, the PFN fault indicator remains active and the

ICS1700A shuts down. A reset must be issued to restart the

controller after installing the battery.