LTC2960
APPLICATIONS INFORMATION
V
MAX 200V
When a supply voltage is abruptly connected to the input
resonantringingcanoccurasaresultofseriesinductance.
The peak voltage could rise to 2x the input supply but in
practice can reach 2.5x if a capacitor with a strong volt-
age coefficient is present. If a 12V supply is hot plugged
IN
RZ
143k
PWC1206LF143kJ*
V
CC
Z1
C1
0.1μF
50V
LTC2960
*TT-IRC
BZX84C30
BV = 30V
the resulting ringing could reach the abs max of V . Any
CC
circuit with an input of more than 7V should be scrutinized
for ringing. Circuit board trace inductances of as little as
10nH can produce significant ringing.
(a)
V
IN
RS
20
One effective means to eliminate ringing is to include a
10–100Ω resistance in series with the supply input before
V
CC
theV capacitorshowninFigure7(b).Thisprovidesdamp-
C1
0.1μF
50V
CC
LTC2960
ing for the resonant circuit but imposes a time constant to
V . In Figure 7(b), the time constant of RS and C1 is 2μs.
CC
2960 F07
(b)
Figure 7. Operation with High Voltage Transients
and Hot Swapping
TYPICAL APPLICATIONS
Configurable Regulator UVLO and Low Battery
Indicator
internal switch when it reaches 2.5V. With a threshold of
5.537V the LTC2960 OUT output disables the load before
this occurs in order to prevent damage to the batteries.
In addition to the UVLO signal, the LTC2960 provides a
low battery indicator for the system. Figure 9 shows an
alternative arrangement in which the LTC2960 monitors
the output of the 3.3V regulator to provide a reset signal.
In the circuit of Figure 8, the high voltage open drain
OUT output is used as a configurable UVLO signal for a
switching regulator. A Li-Ion battery can contain protec-
tion circuitry that open circuits its terminals through an
BUCK CONVERTER
V
NOT ALL LT3991 COMPONENTS SHOWN
BAT
6V TO 8.4V
V
OUT
V
V
IN
OUT
3.3V
R3
R4
10M
LT3991
C2
5.11M*
R5
1M
+
+
EN
47μF
16V
Li-Ion
4.2V
V
GND
C1
0.1μF
25V
CC
RT
IN
OUT
+
R2
49.9k
LTC2960-1
Li-Ion
4.2V
ADJ
RST
LOW BATTERY
MR
R1
348k
GND
2960 F08
UVLO FALLING THRESHOLD = 5.537V
RESET FALLING THRESHOLD = 6.33V
*VISHAY-DALE CRCW SERIES 0603 1%
Figure 8. Configurable Regulator UVLO and Low Battery Indicator
2960f
12
Linear Systems [ Linear Systems ]
