EUP8092
Power on Reset (POR)
Battery Charge Current
The EUP8092 resets itself as the input voltage rises
above the POR rising threshold. The V2P8 pin outputs a
2.8V voltage, the internal oscillator starts to oscillate, the
internal timer is reset, and the charger begins to charge
the battery.
The EUP8092 offers on-chip current regulation with
programmable set point. The resistor connected between
the IREF and GND, RIREF, determines the AC charge rate.
There are three ways to program the charge current:
1. driving the IREF pin above 1.3V
2. driving the IREF pin below 0.35V,
3. or using the RIREF as shown in the Typical
Applications.
The EUP8092 has a typical rising POR threshold of 3.4V
and a falling POR threshold of 2.4V.
Signals in a charge cycle are illustrated in Figure 21.
The voltage of IREF is regulated to a 0.8V reference
voltage when not driven by any external source. The
charging current during the constant current mode is
100,000 times that of the current in the RIREF resistor.
Hence, depending on how IREF pin is used, the charge
current is,
V
> 1.3V
500mA
IREF
0.8V
5
R
V
×10 (A)
IREF =
IREF
R
(4)
IREF
< 0.35V
100mA
IREF
The 500mA current is a guaranteed maximum value for
high-power USB port, with the typical value of 450mA.
The 100mA current is also a guaranteed maximum value
for the low-power USB port. This design accommodates
the USB power specification.
Figure 21. Operation Waveforms
Battery Voltage Regulation
The following events initiate a new charge cycle:
• POR,
The voltage regulation feedback is through the VBAT pin.
This input is tied directly to the positive side of the
battery pack. The EUP8092 monitors the battery pack
voltage between the VBAT and GND pins. When the
battery voltage rises to VO(REG) threshold, the voltage
regulation phase begins and the charging current begins
to taper down.
• a new battery being inserted (detected by TEMP pin),
• the battery voltage drops below a recharge threshold
after completing a charge cycle,
• recovery from an battery over-temperature fault,
• or, the EN pin is toggled from GND to floating.
Sleep Mode
As a safety backup, the EUP8092 also monitors the
charge time in the charge mode. If charge is not
terminated within this time period, TIMEOUT, the
EUP8092 turns off the charger and enunciates FAULT on
the FAULT pins.
End-of-Charge (EOC) Current
The EUP8092 enters the low-power sleep mode if
AC-adapter is removed from the circuit. This feature
prevents draining the battery during the absence of input
supply.
Internal Timer
The internal oscillator establishes a timing reference. The
oscillation period is programmable with an external
timing capacitor, CTIME. The oscillator charges the timing
capacitor to 1.5V and then discharges it to 0.5V in one
period, both with 10µA current. The period TOSC is:
The end-of-charge current C/10 sets the level at which
the charger starts to indicate the end of the charge with
the STATUS pin, as shown in Figure 21. The charger
actually does not terminate charging until the end of the
TIMEOUT, as described in the Total Charge Time
section.
6
T
= 0.2 ×10 × C
(seconds)
(5)
OSC
TIME
Recharge
A 15nF capacitor results in a 3ms oscillation period. The
accuracy of the period is mainly dependent on the
accuracy of the capacitance and the internal current
source. The total charge time for the CC mode and CV
mode is limited can be calculated as:
After End-of-charge, the EUP8092 re-starts the charge
once the voltage on the VBAT pin falls below the V(RCH)
threshold. This feature keeps the battery at full capacity
at all times.
DS8092 Ver 0.2 July 2008
12
EUTECH [ EUTECH MICROELECTRONICS INC ]
