Datasheet

LT3581
9
3581fa
For more information www.linear.com/LT3581
SHDN < 1.33V (TYPICAL)
or
V
IN
< 2.3V (TYPICAL)
SHDN > 1.33V (TYPICAL)
AND
V
IN
> 2.3V (TYPICAL)
FAULT DETECTED
• SS CHARGES UP
• IGATE OFF
• FAULT PIN PULLED LOW
INTERNALLY BY LT3581
• SWITCHER DISABLED
• CLKOUT DISABLED
SS < 50mV
IF |V
OUT
| DROPS CAUSING:
FB < 1.17V (BOOST)
OR
FB > 45mV (INVERTING)
FAULT1
FAULT1
SS > 1.8V AND
NO FAULT1 CONDITIONS
STILL DETECTED
SS < 50mV
FAULT1
FAULT1
FAULT1
FAULT1
FAULT2
FAULT PIN > 1.0V
FAULT1 = OVER VOLTAGE PROTECTION ON V
IN
(V
IN
> 22V MIN)
OVER TEMPERATURE (T
JUNCTION
> 165°C)
OVER CURRENT ON SW1 (I
SW1
> 1.9A MIN)
OVER VOLTAGE PROTECTION ON SW1 (V
SW1
> 42V MIN)
OVER VOLTAGE PROTECTION ON SW2 (V
SW2
> 42V MIN)
FAULT2 = FAULT PULLED LOW EXTERNALLY (FAULT < 0.75V)
CHIP OFF
• ALL SWITCHES DISABLED
• I
GATE
OFF
• FAULTS CLEARED
INITIALIZE
• SS PULLED LOW
NORMAL MODE
• NORMAL OPERATION
• CLKOUT ENABLED WHEN
SS > 1.8V
SAMPLE MODE
• Q1 & Q2 SWITCHES
FORCED ON EVERY CYCLE
FOR AT LEAST MINIMUM
ON TIME
• I
GATE
FULLY ACTIVATED
WHEN SS > 500mV
SOFT START
• I
GATE
ENABLED
• SS CHARGES UP
• SWITCHER ENABLED
POST FAULT DELAY
• SS SLOWLY DISCHARGES
LOCAL FAULT OVER
• INTERNAL FAULT PIN PULLDOWN
RELEASED BY LT3581
• SS CONTINUES DISCHARGING
TO GND
3581 SD
sTaTe DiagraM
Figure 2. State Diagram