Datasheet

LTC3864
24
3864f
APPLICATIONS INFORMATION
Table 2
FAILURE MODE V
OUT
I
OUT
I
VIN
f
RECOVERY
WHEN
FAULT IS
REMOVED? BEHAVIOR
None 5V 1A 453mA 350kHz N/A Normal Operation.
Pin Open
Open Pin 1 (PLLIN/MODE) 5V 1A 453mA 350kHz OK Pin already left open in normal application, so no difference.
Open Pin 2 (FREQ) 5V 1A 453mA 535kHz OK Frequency jumps to default open value.
Open Pin 3 (GND) 5V 1A 453mA 350kHz OK Exposed pad still provides GND connection to device.
Open Pin 4 (SS) 5V 1A 453mA 350kHz OK External soft-start removed, but internal soft-start still available.
Open Pin 5 (VFB) 0V 0A 0.7mA 0kHz OK Controller stops switching. V
FB
internally self biases HI to prevent
switching.
Open Pin 6 (ITH) 5V 1A 507mA 40kHz OK Output still regulating, but the switching is erratic. Loop not stable.
Open Pin 7 (PGOOD) 5V 1A 453mA 350kHz OK No PGOOD output, but controller regulates normally.
Open Pin 8 (RUN) 5V 1A 453mA 350kHz OK Controller does not start-up.
Open Pin 9 (CAP) 5V 1A 453mA 350kHz OK More jitter during switching, but regulates normally.
Open Pin 10 (SENSE) 0V 0A 0.7mA 0kHz OK SENSE internally prebiases to 0.6V below V
IN
. This prevents
controller from switching.
Open Pin 11 (V
IN
) 5.4V 1A 597mA 20kHz OK V
IN
able to bias internally through SENSE. Regulates with high V
OUT
ripple.
Open Pin 12 (GATE) 0V 0A 0.7mA 0kHz OK Gate does not drive external power FET, preventing output regulation.
Open Pin 13 (PGND) 5V 453mA 350kHz OK Pin 3 (GND) still provides GND connection to device.
Pins Shorted
Short Pins 1, 2
(PLLIN/MODE and FREQ)
5V 1A
453mA 350kHz OK Burst Mode operation disabled, but runs normally as in pulse-skipping
mode.
Short Pins 2, 3
(FREQ and GND)
5V 1A 453mA 0kHz OK FREQ already shorted to GND, so regulates normally.
Short Pins 3, 4
(GND and SS)
0V 0A 0.7mA 0kHz OK SS short to GND prevents device from starting up.
Short Pins 4, 5
(SS and VFB)
1V(DC)
3V
P-P
50mA 9mA Erratic OK V
OUT
oscillates from 0V to 3V.
Short Pins 5, 6
(VFB and ITH)
3.15V 625mA 181mA 350kHz OK Controller loop does not regulate to proper output voltage.
Short Pins 7, 8
(PGOOD and RUN)
5V 1A 453mA 350kHz OK Controller does not start-up.
Short Pins 8, 9
(RUN and CAP)
5V 1A 453mA 350kHz OK Able to start-up and regulate normally.
Short Pins 9, 10
(CAP and SENSE)
0V 0A 181mA 0kHz OK CAP ~ V
IN
, which prevents turning on external P-MOSFET.
Short Pins 10, 11
(SENSE and VIN)
5V 1A 453mA 50kHz OK Regulates with high V
OUT
ripple.
Short Pins 11, 12
(VIN and GATE)
0V 0A 29mA 0kHz OK Power MOSFET is always kept OFF, preventing regulation.