LTC4088-1_12 LINER [Linear Technology], LTC4088-1_12 Datasheet - Page 21

• Manufacturer Part Number: LTC4088-1_12
• Description: High Efficiency Battery Charger/USB Power Manager
• Manufacturer: LINER [Linear Technology]

applicaTions inForMaTion
Battery Charger Stability Considerations
The LTC4088-1/LTC4088-2’s battery charger contains both
a constant-voltage and a constant-current control loop. The
constant-voltage loop is stable without any compensation
when a battery is connected with low impedance leads.
Excessive lead length, however, may add enough series
inductance to require a bypass capacitor of at least 1µF
from BAT to GND.
High value, low ESR multilayer ceramic chip capacitors
reduce the constant-voltage loop phase margin, possibly
resulting in instability. Ceramic capacitors up to 22µF
may be used in parallel with a battery, but larger ceramics
should be decoupled with 0.2Ω to 1Ω of series resistance.
Furthermore, a 4.7µF capacitor in series with a 0.2Ω to 1Ω
resistor from BAT to GND is required to prevent oscillation
when the battery is disconnected.
Typical applicaTion
WALL
USB
M2
with NTC Qualified Charging and Reverse Input Protection
C1, C3: MURATA GRM21BR61A106KE19
C2: MURATA GRM188R71C104KA01
L1: COILCRAFT LPS4018-332MLC
M1, M2: SILICONIX Si2333
R2: VISHAY-DALE NTHS0603N01N1003
High Efficiency Battery Charger/USB Power Manager
C1
10µF
0805
T
R1
100k
R2
100k
µC
0.1µF
0603
C2
V
D0
D1
D2
CHRG
NTC
BUS
8.2
R5
the PROG pin should be kept above 100kHz. Therefore, if
the PROG pin has a parasitic capacitance, C
lowing equation should be used to calculate the maximum
CLPROG PROG
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 with program resistor values as high as 25k.
However, additional capacitance on this node reduces the
maximum allowed program resistor. The pole frequency at
resistance value for R
R
LTC4088-1/
LTC4088-2
R3
2.94k
PROG
R4
499
≤
SW
C/X GND
LTC4088-1/LTC4088-2
2π •100kHz •C
V
GATE
V
OUTS
3.3µH
BAT
OUT
L1
PROG
1
+
M1
Li-Ion
:
408812 TA02
PROG
C3
10µF
0805
LOAD
PROG
, the fol-
21
40881fc