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

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

ing for the resonant circuit but imposes a time constant to

Figure 7. Operation with High Voltage Transients

and Hot Swapping

C1

0.1μF

50V

RZ

143k

PWC1206LF143kJ*

Z1

BZX84C30

BV = 30V

LTC2960

(a)

(b)

C1

0.1μF

50V

RS

20

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

GND

EN

ADJ

RT

GND

MR

RST

OUT

R3

5.11M*

Li-Ion

4.2V

Li-Ion

4.2V

R2

49.9k

6V TO 8.4V

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