LTC4007EUFD-1#TRPBF Linear Technology, LTC4007EUFD-1#TRPBF Datasheet - Page 14

• 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

APPLICATIO S I FOR ATIO
LTC4007-1
Battery Detection
It is generally not good practice to connect a battery while
the charger is running. The timer is in an unknown state
and the charger could provide a large surge current into
the battery for a brief time. The Figure 5 circuit keeps the
charger shut down and the timer reset while a battery is not
connected.
Charger Current Programming
The basic formula for charging current is:
This leaves two degrees of freedom: R
The 3.01k input resistors must not be altered since internal
currents and voltages are trimmed for this value. Pick
R
BAT to be close to 100mV during maximum charger
current. Then R
above equation for R
Table 2. Recommended R
14
SENSE
I
MAX
V
I
R
CHARGE MAX
1.0
2.0
3.0
4.0
REF
PROG
(A)
= 1.19V
by setting the average voltage between C
=
(
R
R
SENSE
SENSE
SWITCH CLOSED
WHEN BATTERY
ADAPTER
)
PROG
0.100
0.050
0.033
0.025
POWER
=
CONNECTED
(Ω) 1%
U
V
REF
•
PROG
I
can be determined by solving the
V
CHARGE MAX
SNS
REF
Figure 5
• .
U
.
3 01
and R
• .
R
3 01
SENSE
(
k
PROG
0.25
0.25
Ω
0.5
0.5
23 DCIN
22 SHDN
R
k
SENSE
LTC4007-1
/
Ω
(W)
)
W
R
Resistor Values
+
PROG
0 035
40071
SENSE
.
F05
R
– .
PROG
V
0 035
and R
26.7
26.7
26.7
26.7
U
(kΩ) 1%
SP
V
PROG
and
.
Charging current can be programmed by pulse width
modulating R
quency higher than a few kHz (Figure 6). C
increased to reduce the ripple caused by the R
switching. The compensation capacitor at ITH will prob-
ably need to be increased also to improve stability and
prevent large overshoot currents during start-up condi-
tions. Charging current will be proportional to the duty
cycle of the switch with full current at 100% duty cycle and
zero current when Q1 is off.
Maintaining C/10 Accuracy
The C/10 comparator threshold that drives the FLAG pin
has a fixed threshold of approximately V
This threshold works well when R
not yield a 10% charging current indication if R
different value. There are situations where a standard
value of R
current when using the preferred R
cases, where the full-scale voltage across R
±20mV of the 100mV full-scale target, the input resistors
connected to CSP and BAT can be adjusted to provide the
desired maximum programming current as well as the
correct FLAG trip point.
For example, the desired max charging current is 2.5A but
the best R
across R
82.5mV, normally R
FLAG trip point is only 5% of maximum charging current.
If the input resistors are reduced by the same amount as
SENSE
SENSE
SENSE
Figure 6. PWM Current Programming
5V
0V
PROG
will not allow the desired value of charging
value is 0.033Ω. In this case, the voltage
at maximum charging current is only
with a switch Q1 to R
PROG
R
PROG
LTC4007-1
would be 30.1k but the nominal
PROG
9
Q1
2N7002
40071
F06
PROG
C
PROG
PROG
is 26.7k, but will
R
102k
PROG
value. In these
Z
SENSE
PROG
PROG
= 400mV.
PROG
at a fre-
must be
is within
PROG
40071f
is a