LTC2954 Linear Technology, LTC2954 Datasheet - Page 13

• Manufacturer Part Number: LTC2954
• Description: Push Button On/Off Controller
• Manufacturer: Linear Technology

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TYPICAL APPLICATIO S
capacitor extends the length of time (beyond 64ms) that
the  P  B input must be held low before releasing the enable
output.
High Voltage Power Path Switching
The high voltage  E  N open drain output of the LTC2954-2
is designed to switch on/off an external power PFET. This
allows a user to connect/disconnect a power supply (or
battery) to its load by toggling the  P  B pin. Figure 7 shows
the LTC2954-2 controlling a two cell Li-Ion battery ap-
plication. The  K  I  L  L pin is connected to the output of the
PFET through a resistive divider. The  K  I  L  L pin serves as
a voltage monitor. When V
Li-Ion BATTERY
Li-Ion BATTERY
SINGLE CELL
SINGLE CELL
OUT
4.2V
4.2V
drops below 6V, causing a
+
+
PARASITICS
CERAMIC
Figure 7. Power Path Control with 6V Under Voltage Detect
U
0.1µF
C4
NOISE
INDUCTANCE
CAPACITANCE
TRACE
TRACE
V
PB
GND ONT
IN
Figure 8. Noisy  P  B Trace
LTC2954-2
C
0.033µF
R5
100K
ONT
5.1k
0.1µF
R6
C5
*
KILL
PDT
INT
EN
V
 K  I  L  L voltage below V
circuit 30µs later. Since the PDT pin is open circuited, the
power down debounce time defaults to 64ms.
 P  B Pin in a Noisy Environment
The rugged  P  B pin is designed to operate in noisy envi-
ronments. Transients below ground (>–6V) and above V
(<33V) will not damage the rugged  P  B pin. Additionally,
the  P  B pin can withstand ESD HBM strikes up to ±10kV.
In order to keep external noise from coupling inside the
LTC2954, place an R-C network close to the  P  B pin. A
5.1k resistor and a 0.1µF capacitor should suffice for most
noisy applications (see Figure 8).
IN
V
TH
= 0.6V INPUT
R9
100K
GND
V
PB
IN
M1
*OPTIONAL
DETAILS OMITTED
FOR CLARITY
LTC2954-1
ONT
100k
1%
R4
KILL
PDT
INT
EN
 K  I  L  L (TH)
OPTIONAL GLITCH
FILTER CAPACITOR
R1
909k
1%
2954 F08
V
OUT
V
OUT
,TRIP POINT = 6V
, the  E  N pin becomes an open
C3*
0.1µF
2954 F07
LTC2954
13
2954f
IN