Datasheet

LTC4099
31
4099fd
High value, low ESR multilayer ceramic chip capacitors
reduce the constant-voltage loop phase margin, possibly
resulting in instability. Ceramic capacitors up to 100µF may
be used in parallel with a battery, but larger ceramics should
be decoupled with 0.2
Ω to
1Ω of series resistance.
Furthermore, a 100µF MLCC in series with a 0.3Ω resistor
or
a 100µF OS-CON capacitor from BAT to GND is required
to prevent oscillation when the battery is disconnected.
In constant-current mode, the PROG pin is in the feed
-
back loop rather than the battery voltage. Because of the
additional pole created by any PROG pin capacitance,
capacitance on this pin must be kept to a minimum. With
no additional capacitance on the PROG pin, the charger is
stable for program resistor values as high as 25k. However,
additional capacitance on this node reduces the maximum
allowed program resistor. The pole frequency at the PROG
pin should be kept above 100kHz. Therefore, if the PROG
pin has a parasitic capacitance, C
PROG
, the following equa-
tion should be used to calculate the maximum resistance
value for R
PROG
:
R
PROG
≤
1
2π • 100kHz • C
PROG
applicaTions inForMaTion
Typical applicaTions
High Efficiency USB/Automotive Battery Charger with Overvoltage Protection,
Reverse-Voltage Protection and Low Battery Start-Up
V
BUS
V
OUT
V
C
WALL ACPR
AUTOMOTIVE,
FIREWIRE, ETC.
USB
TO µC
TO µC
SYSTEM
LOAD
M4
C3
22µF
0805
C1
4.7µF
50V
C5
22µF
0805
C2
0.1µF
10V
C4
0.1µF
0603
R5
100k
1
7
8
19 7 9, 21 6
9
3
4 18
14
12
10
11
6
5
4
13
D3
D1
D2
M3
R7
3.01k
R8
1.02k
R3
L2
3.3µH
L1
4.7µH
4099 TA02
CLPROG PROG
LTC4099
LT3653
GND
SW
BATSENS
OVGATE
OVSENS
I
2
C
IRQ
NTCBIAS
NTC
1
20
15-17
8
3
2
V
OUT
IDGATE
BAT
Li-Ion
5
2
+
R6
100k
T
R1
M1
M2
M1, M2, M4: Si2333DS
M3: NTLJS4114N
R4
6.2k
V
IN
GND V
C
HVOK
I
SENSE
I
LIM
SW
BOOST
3
R2
27.4k