LTC4010CFEPBF LINER [Linear Technology], LTC4010CFEPBF Datasheet - Page 13

• Manufacturer Part Number: LTC4010CFEPBF
• Description: High Efficiency Standalone Nickel Battery Charger
• Manufacturer: LINER [Linear Technology]

operaTion
the average current through R
the error amplifier is a scaled control current for the input
of the PWM comparator CC. The I
peak current threshold for CC such that the desired aver-
age current through R
comparator output does this by switching the state of the
SR latch at the appropriate time.
At the beginning of each oscillator cycle, the PWM clock
sets the SR latch and the external P-channel MOSFET is
switched on (N-channel MOSFET switched off) to refresh
the current carried by the external inductor. The inductor
current and voltage drop across R
linearly. During normal operation, the PFET is turned
off (NFET on) during the cycle by CC when the voltage
difference across R
the output of EA. The inductor current then ramps down
linearly until the next rising PWM clock edge. This closes
the loop and maintains the desired average charge current
in the external inductor.
SENSE
(Refer to Figure 1)
SENSE
reaches the peak value set by
is maintained. The current
SENSE
TH
SENSE
. The I
• R3 product sets a
begin to rise
TH
output of
Low Dropout Charging
After charging is initiated, the LTC4010 does not require
that V
ations exist where low dropout charging might occur. In
one instance, parasitic series resistance may limit PWM
headroom (between V
reached. A second case can arise when the DC adapter
selected by the end user is not capable of delivering the
current programmed by R
age of the adapter to collapse. While in low dropout, the
LTC4010 PWM runs near 100% duty cycle with a frequency
that may not be constant and can be less than 550kHz.
The charge current will drop below the programmed value
to avoid generating audible noise, so the actual charge
delivered to the battery may depend primarily on the
LTC4010 charge timer.
Internal Die Temperature
The LTC4010 provides internal overtemperature detection
to protect against electrical overstress, primarily at the
FET driver outputs. If the die temperature rises above this
thermal limit, the LTC4010 stops switching and indicates
a fault as previously discussed.
CC
remain at least 500mV above BAT because situ-
CC
SENSE
and BAT) as 100% charge is
, causing the output volt-
LTC4010

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