LTC4099 Linear Technology Corporation, LTC4099 Datasheet - Page 15

• Manufacturer Part Number: LTC4099
• Description: I2C Controlled USB Power Manager/Charger
• Manufacturer: Linear Technology Corporation

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TO AUTOMOTIVE,
FROM USB
OPERATION
When the switching regulator is activated, the average
input current will be limited by the CLPROG programming
resistor according to the following expression:
where I
V
R
h
sample current delivered to CLPROG. Refer to the Electri-
cal Characteristics table for values of h
and I
specifi cation for the average input current in 100mA or
500mA mode will not be violated, provided that R
is 3.01k or greater. See Table 2 for other available settings
of input current limit.
While not in current limit, the switching regulator’s
Bat-Track feature will set V
OR WALL
ADAPTER
FIREWIRE, ETC.
CLPROG
CLPROG
CLPROG
I
VBUS
VBUSQ
VBUSQ
is the ratio of the measured current at V
is the CLPROG servo voltage in current limit,
is the value of the programming resistor and
I
. Given worst-case circuit tolerances, the USB
VBUSQ
is the quiescent current of the LTC4099,
20
13
19
1
OVSENS
OVGATE
V
CLPROG
BUS
R
V
CLPROG
CLPROG
OVERVOLTAGE PROTECTION
I
SWITCH
1.18V
2
OUT
/N
•
AVERAGE INPUT
CURRENT LIMIT
CONTROLLER
to approximately 300mV
h
–
+
CLPROG
–
+
GATE DRIVE
PWM AND
+–
CLPROG
1
Figure 1. PowerPath Block Diagram
AVERAGE OUTPUT
VOLTAGE LIMIT
CONTROLLER
, V
BUS
6V
CLPROG
CLPROG
–
+
+
to the
4
3.6V
V
HV
V
C
C
IN
0.3V
+ –
HIGH VOLTAGE
STEP-DOWN
REGULATOR
SWITCHING
above the voltage at BAT. However, if the voltage at BAT is
below 3.3V, and the load requirement does not cause
the switching regulator to exceed its current limit, V
will regulate at a fi xed 3.6V, as shown in Figure 2. This
instant-on feature will allow a portable product to run im-
mediately when power is applied without waiting for the
CONSTANT-CURRENT
CONSTANT-VOLTAGE
BATTERY CHARGER
SW
–
+
+
FB
Bat-Track HV CONTROL
V
3.6V
BAT + 0.3V
4.5
4.2
3.9
3.6
3.3
3.0
2.7
2.4
OUT
2.4
OmV
IDEAL
DIODE
15mV
2.7
NO LOAD
Figure 2. V
4.3V
–
+
5
+
–
WALL
3.0
–
+
BAT (V)
BATSENS
3.3
OUT
IDGATE
ACPR
V
OUT
BAT
SW
vs BAT
3.6
18
14
12
10
11
6
300mV
4099 F01
3.9
LTC4099
4099 F02
+
4.2
SINGLE-CELL
Li-Ion
OPTIONAL
EXTERNAL
IDEAL DIODE
PMOS
15
3.5V TO
(BAT + 0.3V)
TO SYSTEM
LOAD
OUT
4099f