Datasheet

LT3579/LT3579-1
9
35791fa
For more information www.linear.com/LT3579
SHDN < 1.33V
OR
V
IN
< 2.3V
SHDN > 1.33V
AND
V
IN
> 2.3V
FAULT DETECTED
• SS CHARGES UP
• IGATE OFF
• FAULT PULLED LOW INTERNALLY BY LT3579
• SWITCHER DISABLED
• CLKOUT DISABLED
SS < 50mV
IF |V
OUT
| DROPS CAUSING:
FB < 1.17V (BOOST)
OR
FB > 45mV (INVERTING)
SS > 1.8V
AND NO FAULT1
CONDITIONS STILL DETECTED
SS < 50mV
FAULT1
FAULT1
FAULT1
FAULT1
FAULT1
FAULT1
FAULT2
FAULT > 1.0V
FAULT1 = OVER VOLTAGE PROTECTION ON V
IN
(V
IN
> 16.2V (MIN))
OVER TEMPERATURE (T
JUNCTION
> 165°C (TYP))
OVER CURRENT ON SW1 (I
SW1
> 3.4A (MIN))
OVER VOLTAGE PROTECTION ON SW1 (V
SW1
> 42V (MIN))
OVER VOLTAGE PROTECTION ON SW1 (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 PULLDOWN
RELEASED BY LT3579
• SS CONTINUES DISCHARGING
TO GND
35791 SD
STATE DIAGRAM
Figure 2. State Diagram