Datasheet

3
LT1676
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Timing
f Switching Frequency 90 100 110 kHz
● 85 115 kHz
Maximum Switch Duty Cycle ● 85 90 %
t
ON(MIN)
Minimum Switch On Time High dV/dt Mode, R
L
= 50Ω (Note 4) 300 ns
Boost Operation
V
C
Pin Boost Threshold 1.35 V
dV/dt Below Threshold 0.2 V/ns
dV/dt Above Threshold 1.6 V/ns
Sync Function
Minimum Sync Amplitude ● 1.5 2.2 V
Synchronization Range ● 130 250 kHz
SYNC Pin Input R 40 kΩ
SHDN Pin Function
V
SHDN
Shutdown Mode Threshold 0.5 V
● 0.2 0.8 V
Upper Lockout Threshold Switching Action On 1.260 V
Lower Lockout Threshold Switching Action Off 1.245 V
I
SHDN
Shutdown Pin Current V
SHDN
= 0V 12 20 µA
V
SHDN
= 1.25V 2.5 10 µA
V
IN
= 48V, V
SW
open, V
CC
= 5V, V
C
= 1.4V unless otherwise noted.
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
TEMPERATURE (°C)
–50
7.4
7.2
7.0
6.8
6.6
6.4
6.2
6.0
25 75
LT1676 G01
–25 0
50 100 125
INPUT VOLTAGE (V)
Minimum Input Voltage vs
Temperature
SWITCH CURRENT (mA)
0
SWITCH VOLTAGE (V)
1.50
1.25
1.00
0.75
0.50
0.25
0
300 500
1676 G02
100 200
400 600 700
125°C
–55°C
25°C
DUTY CYCLE (%)
0
SWITCH CURRENT LIMIT (mA)
1000
800
600
400
200
0
80
1676 G03
2010 30 50 70 90
40
60
100
T
A
= 25°C
Switch Current Limit vs
Duty Cycle
Switch-On Voltage vs
Switch Current
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Control circuitry powered from V
CC
.
Note 3: Switch current limit is DC trimmed and tested in production.
Inductor dl/dt rate will cause a somewhat higher current limit in actual
application.
Note 4: Minimum switch on time is production tested with a 50Ω resistive
load to ground.
TYPICAL PERFORMANCE CHARACTERISTICS
UW