Datasheet

LTC2960
12
2960f
When a supply voltage is abruptly connected to the input
resonant ringing can occur as a result of series inductance.
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
the resulting ringing could reach the abs max of V
CC
. Any
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.
One effective means to eliminate ringing is to include a
10–100Ω resistance in series with the supply input before
the V
CC
capacitor shown in Figure 7(b). This provides damp-
ing for the resonant circuit but imposes a time constant to
V
CC
. In Figure 7(b), the time constant of RS and C1 is 2μs.
Figure 7. Operation with High Voltage Transients
and Hot Swapping
C1
0.1μF
50V
RZ
143k
PWC1206LF143kJ*
V
CC
Z1
BZX84C30
BV = 30V
V
IN
MAX 200V
LTC2960
(a)
(b)
C1
0.1μF
50V
RS
20
V
IN
V
CC
LTC2960
2960 F07
*TT-IRC
TYPICAL APPLICATIONS
Figure 8. Configurable Regulator UVLO and Low Battery Indicator
Configurable Regulator UVLO and Low Battery
Indicator
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
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.
LTC2960-1
LT3991
V
IN
V
CC
GND
V
OUT
EN
ADJ
RT
GND
MR
IN
+
RST
OUT
R3
5.11M*
Li-Ion
4.2V
Li-Ion
4.2V
R2
49.9k
V
BAT
6V TO 8.4V
V
OUT
3.3V
C1
0.1μF
25V
R1
348k
LOW BATTERY
R5
1M
R4
10M
2960 F08
C2
47μF
16V
UVLO FALLING THRESHOLD = 5.537V
RESET FALLING THRESHOLD = 6.33V
NOT ALL LT3991 COMPONENTS SHOWN
BUCK CONVERTER
+
+
*VISHAY-DALE CRCW SERIES 0603 1%
APPLICATIONS INFORMATION