LTM8062IV#PBF Linear Technology, LTM8062IV#PBF Datasheet - Page 14

• Manufacturer Part Number: LTM8062IV#PBF
• Description: IC, BATT CHRG, Li-Ion, Li-Polymer, 2A, LGA77
• Manufacturer: Linear Technology

Specifications of LTM8062IV#PBF

• Battery Type: Li-Ion, Li-Polymer
• Input Voltage: 32V
• Battery Charge Voltage: 14.4V
• Charge Current Max: 2A
• Battery Ic Case Style: LGA
• No. Of Pins: 77
• No. Of Series Cells: 1

APPLICATIONS INFORMATION
LTM8062
Status Pins
The LTM8062 reports charger status through two open-
collector outputs, the CHRG and FAULT pins. These pins can
be pulled up as high as V
CHRG pin indicates that the charger is delivering current at
greater than a C/10 rate, or one-tenth of the programmed
charge current. The FAULT pin signals bad-battery and NTC
faults. These pins are binary coded, as shown in Table 3.
Table 3. Status Pin State
CHRG
High
High
Low
Low
If the battery is removed from an LTM8062 charger that is
configured for C/10 termination, a low amplitude sawtooth
waveform appears at the charger output, due to cycling
between termination and recharge events. This cycling
results in pulsing at the CHRG output. An LED connected
to this pin will exhibit a blinking pattern, indicating to the
user that a battery is not present. The frequency of this
blinking pattern is dependent on the output capacitance.
C/10 Charge Termination
The LTM8062 supports a low current based termination
scheme, where a battery charge cycle terminates when
the charge current falls below one-tenth the programmed
charge current, or approximately 200mA. This termination
mode is engaged by shorting the TMR pin to ground. When
C/10 termination is used, an LTM8062 charger sources
battery charge current as long as the average current level
remains above the C/10 threshold. As the full-charge float
voltage is achieved, the charge current falls until the C/10
threshold is reached, at which time the charger terminates
and the LTM8062 enters standby mode. The CHRG status
pin follows the charger cycle and is high impedance when
the charger is not actively charging. There is no provision
for bad-battery detection if C/10 termination is used.
Timer Charge Termination
The LTM8062 supports a timer-based termination scheme,
where a battery charge cycle terminates after a specific
amount of time elapses. Timer termination is engaged
14
FAULT
High
Low
High
Low
STATUS
Not Charging—Standby or Shutdown Mode
Bad-Battery Fault (Precondition Timeout/EOC Failure)
Normal Charging at C/10 or Greater
NTC Fault (Pause)
IN
, and can sink up to 10mA. The
when a capacitor (C
to ground. The timer cycle time span (t
by C
When charging at a 1C rate, t
hours, which requires a 0.68μF capacitor.
The CHRG status pin continues to signal charging, regard-
less of which termination scheme is used. When timer
termination is used, the CHRG status pin is pulled low
during a charge cycle until the charge current falls below
the C/10 threshold. The charger continues to top off the
battery until timer EOC, when the LTM8062 terminates the
charge cycle and enters standby mode.
Termination at the end of the timer cycle only occurs if the
charge cycle was successful. A successful charge cycle
occurs when the battery is charged to within 2.5% of the
full-charge float voltage. If a charge cycle is not success-
ful at EOC, the timer cycle resets and charging continues
for another full timer cycle. When V
the full-charge float voltage, whether by battery loading
or replacement of the battery, the charger automatically
resets and starts charging.
Preconditioning and Bad-Battery Fault
The LTM8062 has a precondition mode, where the charge
current is limited to 15% of the maximum charge current, or
approximately 300mA. Precondition mode is engaged if the
voltage on the BAT pin is below the precondition threshold,
or approximately 70% of the float voltage. Once the BAT
voltage rises above the precondition threshold, normal full-
current charging can commence. The LTM8062 incorporates
90mV hysteresis to avoid spurious mode transitions.
Bad-battery detection is engaged when the internal timer
is used for termination (capacitor tied to TMR). This fault
detection feature is designed to identify failed cells. A
bad-battery fault is triggered when the voltage on BAT
remains below the precondition threshold for greater
than one-eighth of a full timer cycle (one-eighth EOC). A
bad-battery fault is also triggered if a normally charging
battery re-enters precondition mode after one-eighth EOC.
When a bad-battery fault is triggered, the charge cycle
is suspended, and the CHRG status pin becomes high
C
TIMER
TIMER
= t
in the equation:
EOC
• 2.27 • 10
TIMER
) is connected from the TMR pin
–7
EOC
(Hours)
is commonly set to three
BAT
EOC
drops 2.5% from
) is determined
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