LTC4007EUFD-1#TRPBF Linear Technology, LTC4007EUFD-1#TRPBF Datasheet - Page 20

• Manufacturer Part Number: LTC4007EUFD-1#TRPBF
• Description: IC CHARGER BATTERY 4A 24-QFN
• Manufacturer: Linear Technology
• Type: Battery Chargerr

Specifications of LTC4007EUFD-1#TRPBF

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion)
• Voltage - Supply: 6 V ~ 28 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-WFQFN Exposed Pad
• Output Current: 4A
• Output Voltage: 4.1/4.2V
• Operating Supply Voltage (min): 6V
• Operating Supply Voltage (max): 28V
• Operating Temp Range: -40C to 85C
• Package Type: QFN
• Mounting: Surface Mount
• Pin Count: 24
• Operating Temperature Classification: Industrial
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC4007-1
APPLICATIO S I FOR ATIO
Disabling the Thermistor Function
If the thermistor is not needed, connecting a resistor
between DCIN and NTC will disable it. The resistor should
be sized to provide at least 10µA with the minimum voltage
applied to DCIN and 10V at NTC. Do not exceed 30µA.
Generally, a 301k resistor will work for DCIN less than 15V.
A 499k resistor is recommended for DCIN between 15V
and 24V.
Conditioning Depleted Batteries
Severely depleted batteries, with less than 3.25V/cell,
should be conditioned with a trickle charge to prevent
possible damage. This trickle charge is typically 10% of
the 1C rate of the battery. The LTC4007-1 can automati-
cally trickle charge depleted batteries using the circuit in
Figure 11. If the battery voltage is less than 3.25V/cell
(3.173V/cell if CHEM is low) then the LOBAT indicator will
be low and Q4 is off. This programs the charging current
with R
300mA. When the cell voltage becomes greater than 3.25V
the LOBAT indicator goes high, Q4 shorts out R13, then
R
PCB Layout Considerations
For maximum efficiency, the switch node rise and fall
times should be minimized. To prevent magnetic and
electrical field radiation and high frequency resonant prob-
lems, proper layout of the components connected to the IC
is essential. (See Figure 12.) Here is a PCB layout priority
list for proper layout. Layout the PCB using this specific
order.
20
PROG
PROG
= R6. Charging current is then equal to 3A.
= R6 + R14. Charging current is approximately
U
U
W
U
General Rules
1. Input capacitors need to be placed as close as possible
2. The control IC needs to be close to the switching FET’s
3. Place inductor input as close as possible to switching
4. Place the output current sense resistor right next to
5. Place output capacitors next to the sense resistor
6. Output capacitor ground connections need to feed
to switching FET’s supply and ground connections.
Shortest copper trace connections possible. These
parts must be on the same layer of copper. Vias must
not be used to make this connection.
gate terminals. Keep the gate drive signals short for a
clean FET drive. This includes IC supply pins that con-
nect to the switching FET source pins. The IC can be
placed on the opposite side of the PCB relative to above.
FET’s output connection. Minimize the surface area of
this trace. Make the trace width the minimum amount
needed to support current—no copper fills or pours.
Avoid running the connection using multiple layers in
parallel. Minimize capacitance from this node to any
other trace or plane.
the inductor output but oriented such that the IC’s
current sense feedback traces going to resistor are not
long. The feedback traces need to be routed together
as a single pair on the same layer at any given time with
smallest trace spacing possible. Locate any filter
component on these traces next to the IC and not at the
sense resistor location.
output and ground.
into same copper that connects to the input capacitor
ground before tying back into system ground.
40071f