Datasheet

LT3688
3
3688f
The l denotes the specifi cations which apply over the full operating
junction temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 12V, unless otherwise noted. (Note 3)
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Undervoltage Lockout
l
3 3.5 3.8 V
Quiescent Current from V
IN
V
EN/UVLO
= 0.3V
V
BIAS
= 5V, Not Switching
V
BIAS
= 0V, Not Switching
l
0.01
65
235
1
105
310
µA
µA
µA
Quiescent Current from BIAS V
EN/UVLO
= 0.3V
V
BIAS
= 5V, Not Switching
V
BIAS
= 0V, Not Switching
l
0.01
155
–5
1
200
–20
µA
µA
µA
FB Voltage
l
0.790
0.784
0.800 0.810
0.814
V
V
FB Pin Bias Current V
FB
= 0.800V
l
–3 –50 nA
FB Voltage Line Regulation 5V < V
IN
< 36V 0.002 %/V
Switching Frequency R
T
= 20k, V
BST
= 12V
R
T
= 110k, V
BST
= 12V
l
l
1.85
460
2.1
500
2.35
540
MHz
kHz
Minimum Off-Time (Note 4) V
BST
= 12V
l
115 180 ns
Switch Current Limit (Note 5) DC = 15%
l
1.2 1.7 2.2 A
Switch V
CESAT
I
SW
= 0.8A 280 mV
Switch Leakage Current (Note 8) –0.01 –1 µA
DA Current Limit
l
0.9 1.2 1.6 A
Boost Schottky Reverse Leakage V
BIAS
= 0V 0.01 2 µA
Minimum BST Voltage above SW 2.15 2.5 V
BST Pin Current I
SW
= 0.8A 15 25 mA
EN/UVLO Threshold Voltage
l
1.15 1.25 1.35 V
EN/UVLO Input Current V
EN/UVLO
= 1.35V
V
EN/UVLO
= 1.15V 2.5
0.3
46
µA
µA
Threshold Current Hysteresis 2.5 3.7 5.5 µA
RUN/SS Pin Current V
RUN/SS
= 0V –1.4 –2.8 –4 µA
RUN/SS Switching Threshold 0.15 0.8 1 V
SYNC Threshold Voltage 0.4 0.8 1.3 V
V
UV
Reset Threshold % of FB Voltage, V
FB
Falling
l
88 90 92 %
t
RST
Reset Timeout Period C
POR
= 4700pF
l
21.2 23.5 25.8 ms
t
WDU
Watchdog Window Upper Boundary C
WDT
= 1000pF
l
18 20 22 ms
t
WDL
Watchdog Window Lower Boundary C
WDT
= 1000pF
l
0.8 1.25 1.6 ms
t
WDTO
Watchdog Timeout Period C
WDT
= 1000pF 2.5 ms
RST Output Voltage Low I
SINK
= 2.5mA, V
FB
= 0.6V
I
SINK
= 100µA, V
FB
= 0.6V
l
l
0.2
0.01
0.4
0.3
V
V
t
UV
UV Detect to RST Asserted V
FB
Set to 0.680V
l
41030 µs
WDI Input Threshold
l
0.4 0.95 1.3 V
WDI Input Pull-Up Current –2 µA
WDI Input Pulse Width
l
300 ns
WDE Threshold Voltage
l
0.4 0.65 1 V
WDE Input Pull-Down Current V
WDE
= 1.2V 3.5 µA
WDO Output Voltage Low I
SINK
= 2.5mA
I
SINK
= 100µA
l
l
0.2
0.01
0.4
0.3
V
V