LTC4011CFE#TR Linear Technology, LTC4011CFE#TR Datasheet - Page 13

• Manufacturer Part Number: LTC4011CFE#TR
• Description: IC BATT CHARGER HIEFF 20TSSOP
• Manufacturer: Linear Technology

Specifications of LTC4011CFE#TR

• Function: Charge Management
• Battery Type: Nickel Cadmium (NiCd), Nickel Metal-Hydride (NiMH)
• Voltage - Supply: 4.5 V ~ 34 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

operaTion
Top-Off Charge State
If NiMH fast charge termination occurs because the
∆T/∆t limit is exceeded after an initial period of t
has expired, the LTC4011 enters the top-off charge state.
Top-off charge is implemented by sourcing one-tenth the
programmed charge current for t
that 100% charge has been delivered to the battery. The
CHRG and TOC status outputs are active during the top-off
state. If NiCd cells have been selected with the CHEM pin,
the LTC4011 never enters the top-off state.
Automatic Recharge State
Once charging is complete, the automatic recharge state
is entered to address the self-discharge characteristics
of nickel chemistry cells. The charge status outputs are
inactive during automatic recharge, but V
switched to GND to monitor the average cell voltage. If the
V
350mV, the charge timer is reset and a new fast charge
cycle is initiated.
The internal termination algorithms of the LTC4011 are
adjusted when a fast charge cycle is initiated from auto-
matic recharge, because the battery should be almost fully
charged. Voltage-based termination is enabled immediately
and the NiMH ∆T/∆t limit is fixed at a battery temperature
rise of 1°C/minute.
Fault State
As discussed previously, the LTC4011 enters the fault state
based on detection of invalid battery voltages during vari-
ous charging phases. The IC also monitors the regulation
of the PWM control loop and will enter the fault state if
this is not within acceptable limits. Once in the fault state,
the battery must be removed or DC input power must be
cycled in order to initiate further charging. In the fault
state, the FAULT output is active, the READY output is
inactive, charging stops and the charge indicator outputs
are inactive. The V
to allow detection of battery removal.
Note that the LTC4011 also uses the FAULT output to indi-
cate that charging is suspended due to invalid battery or
internal die temperatures. However, the IC does not enter
the fault state in these cases and normal operation will
CELL
voltage drops below 1.325V without falling below
CDIV
output remains connected to GND
MAX
/3 minutes to ensure
CDIV
remains
MAX
/12
resume when all temperatures return to acceptable levels.
Refer to the Status Outputs section for more detail.
Insertion and Removal of Batteries
The LTC4011 automatically senses the insertion or removal
of a battery by monitoring the V
this voltage fall below 350mV, the IC considers the bat-
tery to be absent. Removing and then inserting a battery
causes the LTC4011 to initiate a completely new charge
cycle beginning with charge qualification.
External Pause Control
After charging is initiated, the V
pause operation at any time. When the voltage between
V
pauses, fast charge termination algorithms are inhibited
and the PWM outputs are disabled. The status and V
outputs all remain active. Normal function is fully restored
from the previous state when pause ends.
Status Outputs
The LTC4011 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 four status outputs and the
V
outputs can directly drive current-limited LEDs terminated
to the DC input. The V
informational. V
resistor divider, as previously discussed.
Table 1. LTC4011 Status Pins
READY FAULT
Off
On
On
On
On
Off
TEMP
CDIV
pin as a function of LTC4011 operation. The status
and GND drops below 200mV, the charge timer
Off
Off
Off
Off
On
On
On or Off On or Off
CHRG
Off
Off
Off
On
On
CDIV
should only be used for the V
TOC
Off
Off
Off
On
Off
CDIV
column in Table 1is strictly
V
Off
On
On
On
On
On
CDIV
TEMP
CELL
Precharge or Fast Charge
pin voltage. Should
pin may be used to
or Automatic Recharge
NiMH Top-Off Charge
Fault State (Latched)
Temperature Limits
(V
CHARGER STATE
(May be Paused)
(May be Paused)
Ready to Charge
LTC4011
TEMP
Exceeded
Held Low)
Off

CELL
CDIV
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