LTC4099EPDC データシートの表示（PDF） - Linear Technology
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LTC4099EPDC Datasheet PDF : 36 Pages
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Operation
LTC4099
TO AUTOMOTIVE,
FIREWIRE, ETC.
HVIN
HIGH VOLTAGE
STEP-DOWN
SW
VC
SWITCHING
REGULATOR
FB
FROM USB
OR WALL
ADAPTER
OVSENS
20
OVGATE
1
OVERVOLTAGE PROTECTION
s2
+–
4
VC
6V
VOUT
3.6V
BAT + 0.3V
5
WALL
–
4.3V +
Bat-Track HV CONTROL
ACPR
18
13 VBUS
ISWITCH/N
PWM AND
GATE DRIVE
CONSTANT-CURRENT
CONSTANT-VOLTAGE
BATTERY CHARGER
IDEAL
DIODE
+
OmV
–
15mV +–
CLPROG
19
–
+
1.18V
AVERAGE INPUT
CURRENT LIMIT
CONTROLLER
0.3V
+–
3.6V
AVERAGE OUTPUT
VOLTAGE LIMIT
CONTROLLER
Figure 1. PowerPath Block Diagram
SW
14
VOUT 12
IDGATE
10
3.5V TO
(BAT + 0.3V)
TO SYSTEM
LOAD
OPTIONAL
EXTERNAL
IDEAL DIODE
PMOS
BAT
11
BATSENS
6
4099 F01
+ SINGLE-CELL
Li-Ion
When the switching regulator is activated, the average
input current will be limited by the CLPROG programming
resistor according to the following expression:
( ) IVBUS
=
IVBUSQ
+
VCLPROG
RCLPROG
•
hCLPROG + 1
where IVBUSQ is the quiescent current of the LTC4099,
VCLPROG is the CLPROG servo voltage in current limit,
RCLPROG is the value of the programming resistor and
hCLPROG is the ratio of the measured current at VBUS to the
sample current delivered to CLPROG. Refer to the Electri-
cal Characteristics table for values of hCLPROG, VCLPROG
and IVBUSQ. Given worst-case circuit tolerances, the USB
specification for the average input current in 100mA or
500mA mode will not be violated, provided that RCLPROG
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 VOUT to approximately 300mV
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, VOUT
will regulate at a fixed 3.6V, as shown in Figure 2. This
instant-on feature will allow a portable product to run
immediately when power is applied without waiting for
4.5
4.2
3.9
NO LOAD
3.6
3.3
300mV
3.0
2.7
2.4
2.4
2.7 3.0 3.3 3.6 3.9 4.2
BAT (V)
4099 F02
Figure 2. VOUT vs BAT
4099fd
15
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