Rainbow Electronics DS2788 - Manual (Page 19)

Fuel-Gauge Display
The DS2788 provides five open-drain drivers capable
of sinking 30mA. These can be used to directly drive
either 4 or 5 LEDs to display Remaining Active Relative
Pack Capacity (RARC). The LEDs are enabled when
the PIO is configured as an input and the PIO pin rec-
ognizes a rising edge. The display lights for 4s and
then is disabled regardless of the state of the PIO pin.
Further presses or releases of the button connected to
the PIO pin after the 100ms debounce delay causes
the display to be enabled (the display does not light
continuously if the button is held down).
Table 2 summarizes how the LEDs are enabled. B sig-
nifies that the LED is blinking at a 50% duty cycle, 0.5s
on, 0.5s off, to be repeated for the display time of 4s. L
signifies the pin is pulled low, and the LED is lit. X signi-
fies the pin is high impedance, and the LED is unlit.
Table 2. Fuel-Gauge Display Summary
D
S
2
7
8
8
Stand-Alone Fuel-Gauge IC with
LED Display Drivers
______________________________________________________________________________________ 19
Special Feature Register
ADDRESS 15h BIT DEFINITION
Field Bit Format Allowable Values
Reserved 1:7 Undefined
PIOSC 0 Read/Write
PIO Sense and Control
Read values:
0: PIO pin
V IL
1: PIO pin  V IH
Write values:
0: Activates PIO pin open-drain output driver, forcing the PIO pin low.
1: Disables the output driver, allowing the PIO pin to be pulled high or used as
an input.
Power-up and SLEEP mode default: 1 (PIO pin is high-Z).
Note: PIO pin has weak pulldown.
Figure 16. Special Feature Register Format
All Special Feature register bits are read and write acces-
sible, with default values specified in each bit definition.
CAPACITY
5 LEDs, DC: 0
LED5–LED1
4 LEDs, DC: 1
LED4–LED1
RARC
10 XXXXB XXXB
10 < RARC
20 XXXXL XXXL
20 < RARC
25 XXXLL XXXL
25 < RARC
40 XXXLL XXLL
40 < RARC
50 XXLLL XXLL
50 < RARC
60 XXLLL XLLL
60 < RARC
75 XLLLL XLLL
75 < RARC
80 XLLLL LLLL
80 < RARC
100 LLLLL LLLL