LTC3864 Datasheet, PDF (24/28 Pages) Linear Technology – 60V Low IQ Step-Down DC/DC Controller with 100% Duty Cycle Capability

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