LTC4010CFEPBF LINER [Linear Technology], LTC4010CFEPBF Datasheet - Page 12

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

LTC4010
operaTion
Status Outputs
The LTC4010 open-drain status outputs provide valuable
information about the IC’s operating state and can be
used for a variety of purposes in applications. Table 1
summarizes the state of the three status outputs and the
V
outputs can directly drive current-limited LEDs terminated
to the DC input. The V
informational. V
V
Table 1. LTC4010 Status Pins

CDIV
CELL
READY
Off
On
On
On
Off
pin as a function of LTC4010 operation. The status
resistor divider, as previously discussed.
FAULT
Off
Off
Off
On
On
CDIV
On or Off
CHRG
should only be used to terminate the
Off
Off
On
Off
(Refer to Figure 1)
CDIV
column in Table 1 is strictly
V
R
Off
CDIV
On
On
On
On
SENSE
V
CC
Precharge, Fast or Top Off
14
12
10
Charge (May be Paused)
9
or Automatic Recharge
LTC4010
Fault State (Latched)
Temperature Limits
TGATE
BGATE
SENSE
BAT
(V
CHARGER STATE
Ready to Charge
TEMP
Exceeded
Figure 2. LTC4010 PWM Control Loop
Off
Held Low)
R1
R2
I
–
+
PROG
Q
EA
S
R
PWM Current Source Controller
An integral part of the LTC4010 is the PWM current source
controller. The charger uses a synchronous step-down
architecture to produce high efficiency and limited thermal
dissipation. The nominal operating frequency of 550kHz
allows use of a smaller external inductor. The TGATE and
BGATE outputs have internally clamped voltage swings.
They source peak currents tailored to smaller surface-
mount power FETs likely to appear in applications providing
an average charge current of 3A or less. During the various
charging states, the LTC4010 uses the PWM controller to
regulate an average voltage between SENSE and BAT that
ranges from 10mV to 100mV.
A conceptual diagram of the LTC4010 PWM control loop
is shown in Figure 2.
The voltage across the external current programming
resistor R
EA. An internal programming current is also pulled from
input resistor R1. The I
desired average voltage drop across R
R3
R4
PWM CLOCK
I
TH
SENSE
CC
is averaged by integrating error amplifier
4010 F02
PROG
• R1 product establishes the
SENSE
, and hence,
4010fb