LTC4066 LINER [Linear Technology], LTC4066 Datasheet - Page 15

• Manufacturer Part Number: LTC4066
• Description: USB Power Controller and Li-Ion Linear Charger with Low Loss Ideal Diode
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
USB Current Limit and Charge Current Control
The current limit and charger control circuits of the
LTC4066/LTC4066-1 are designed to limit input current as
well as control battery charge current as a function of I
The programmed input current limit, I
The programmed battery charge current, I
as:
Input current, I
current and the OUT pin output current:
The current limiting circuitry in the LTC4066/LTC4066-1
can and should be confi gured to limit current to 500mA
for USB applications (selectable using the HPWR pin and
programmed using the CLPROG pin).
–100
I
I
I
600
500
400
300
200
100
CL
CHG
IN
0
0
= I
(2a) High Power Mode/Full Charge
R
=
PROG
=
OUT
⎛
⎜
⎝
100
R
⎛
⎜
⎝
CLPROG
50 000
R
= 100k and R
1000
+ I
PROG
,
IN
200
BAT
, is equal to the sum of the BAT pin output
I
I
LOAD
IN
•
•
300
V
V
(mA)
PROG
CLPROG
CLPROG
400
I
CHARGING
I
BAT
LOAD
⎞
⎟ =
⎠
= 2k
500
⎞
⎟ =
⎠
Figure 2. Input and Battery Currents as a Function of Load Current
(IDEAL DIODE)
50 000
4066 F02a
R
R
,
PROG
I
600
BAT
1000
CLPROG
CL
V
, is defi ned as:
V
120
100
–20
80
20
60
40
CHG
0
0
(2b) Low Power Mode/Full Charge
R
PROG
, is defi ned
20
= 100k and R
OUT
40
I
I
.
LOAD
IN
60
(mA)
The LTC4066/LTC4066-1 reduce battery charge current
such that the sum of the battery charge current and the
load current does not exceed the programmed input current
limit (one-fi fth of the programmed input current limit when
HPWR is low, see Figure 2). The battery charge current
goes to zero when load current exceeds the programmed
input current limit (one-fi fth of the limit when HPWR is
low). If the load current is greater than the current limit, the
output voltage will drop to just under the battery voltage
where the ideal diode circuit will take over and the excess
load current will be drawn from the battery.
Programming Current Limit
The formula for input current limit is:
where V
the total resistance from the CLPROG pin to ground.
For example, if typical 500mA current limit is required,
calculate:
CLPROG
80
I
R
I
CHARGING
I
BAT
LOAD
CL
CLPROG
=
= 2k
100
CLPROG
(IDEAL DIODE)
⎛
⎜
⎝
4066 F02a
R
CLPROG
1000
I
120
BAT
=
500
is the CLPROG pin voltage and R
LTC4066/LTC4066-1
1
V
–100
mA
100
600
500
400
300
200
•
0
V
0
(2c) High Power Mode with
I
R
CLPROG
CL
•
PROG
1000 2
= 500mA and I
100
I
BAT
= 200k and R
= I
⎞
⎟ =
⎠
=
CHG
200
CHARGING
I
k
I
I
R
BAT
IN
LOAD
1000
CLPROG
300
(mA)
CHG
CLPROG
V
400
I
= 250mA
BAT
I
LOAD
= I
CL
500
= 2k
(IDEAL DIODE)
CLPROG
– I
4055 F02c
15
OUT
I
600
BAT
4066fc
is