LTC2954CDDB-1TR View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC2954CDDB-1TR' PDF : 18 Pages View PDF
LTC2954
TYPICAL APPLICATIONS
width detected is 30μs. If there are glitches on the resis-
tor pull-up voltage that are wider than 30μs and transition
below 0.6V, then an appropriate bypass capacitor should
be connected to the KILL pin. The optional CPDT external
capacitor extends the length of time (beyond 64ms) that
the PB input must be held low before releasing the enable
output.
High Voltage PowerPath Switching
The high voltage EN 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 PB pin. Figure 7 shows
the LTC2954-2 controlling a two cell Li-Ion battery ap-
plication. The KILL pin is connected to the output of the
PFET through a resistive divider. The KILL pin serves as
a voltage monitor. When VOUT drops below 6V, causing a
KILL voltage below VKILL(TH), the EN pin becomes an open
circuit 30μs later. Since the PDT pin is open-circuited, the
power-down debounce time defaults to 64ms.
PB Pin in a Noisy Environment
The rugged PB pin is designed to operate in noisy environ-
ments. Transients below ground (>–6V) and above VIN
(<33V) will not damage the rugged PB pin. Additionally,
the PB 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 PB pin. A 5.1k
resistor and a 0.1μF capacitor should suffice for most noisy
applications (see Figure 8).
4.2V
SINGLE CELL
Li-Ion BATTERY
+
C4
0.1μF
CERAMIC
4.2V +
SINGLE CELL
Li-Ion BATTERY
R5
M1
100k
R9
100k
VIN
EN
LTC2954-2 INT
PB
GND ONT
KILL
PDT VTH = 0.6V INPUT
CONT*
0.033μF
*OPTIONAL
R4
100k
1%
VOUT
VOUT,TRIP POINT = 6V
R1
909k
1%
OPTIONAL GLITCH
FILTER CAPACITOR
C3*
0.1μF
2954 F07
Figure 7. PowerPath Control with 6V Undervoltage Detect
PARASITICS
TRACE
CAPACITANCE
NOISE
TRACE
INDUCTANCE
VIN
R6
5.1k
C5
0.1μF
VIN
EN
PB
LTC2954-1 INT
KILL
GND
ONT
PDT
DETAILS OMITTED
FOR CLARITY
2954 F08
Figure 8. Noisy PB Trace
2954fb
13
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