LT3825
3
3825fe
PARAMETER CONDITIONS MIN TYP MAX UNITS
Reference Voltage Line Regulation 12V ≤ V
CC
≤ 18V
l
0.005 0.02 %/V
Feedback Amplifier Voltage Gain V
C
= 1.2V to 1.7V 1400 V/V
Soft-Start Charging Current V
SFST
= 1.5V 16 20 25 µA
Soft-Start Discharge Current V
SFST
= 1.5V, V
UVLO
= 0V 0.8 1.3 mA
Control Pin Threshold (V
C
) Duty Cycle = Min 1.0 V
Gate Outputs
PG, SG Output High Level
l
6.6 7.4 8.0 V
PG, SG Output Low Level
l
0.01 0.05 V
PG, SG Output Shutdown Strength
V
UVLO
= 0V; I
PG
, I
SG
= 20mA
l
1.6 2.3 V
PG Rise Time C
PG
= 1nF 11 ns
SG Rise Time C
SG
= 1nF 15 ns
PG, SG Fall Time C
PG
, C
SG
= 1nF 10 ns
Current Amplifier
Switch Current Limit at Maximum V
C
V
SENSE
+
l
88 98 110 mV
∆V
SENSE
/∆V
C
0.07 V/V
Sense Voltage Overcurrent Fault Voltage V
SENSE
+
l
206 230 mV
Timing
Switching Frequency (f
OSC
) C
OSC
= 100pF
l
84 100 110 kHz
Oscillator Capacitor Value (C
OSC
) (Note 6) 33 200 pF
Minimum Switch On-Time (t
ON(MIN)
) 200 ns
Flyback Enable Delay Time (t
ED
) 265 ns
PG Turn-On Delay Time (t
PGDLY
) 200 ns
Maximum Switch Duty Cycle
l
85 88 %
SYNC Pin Threshold
l
1.53 2.1 V
SYNC Pin Input Resistance 40 kΩ
Load Compensation
Load Comp to V
SENSE
Offset Voltage V
RCMP
with V
SENSE
+
= 0V 1 mV
Feedback Pin Load Compensation Current V
SENSE
+
= 20mV, V
FB
= 1.230V 20 µA
UVLO Function
UVLO Pin Threshold
(V
UVLO
)
l
1.215 1.240 1.265 V
UVLO Pin Bias Current V
UVLO
= 1.2V
V
UVLO
= 1.3V
–0.25
–4.50
0
–3.4
±0.25
–2.50
µA
µA
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 14V; PG, SG Open; V
C
= 1.5V, V
SENSE
–
= 0V; R
CMP
= 1k,
R
tON
= 90k, R
PGDLY
= 27.4k, R
ENDLY
= 90k, unless otherwise specified (Note 3).
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum
Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 3: The LT3825 is tested under pulsed load conditions, such that T
J
≈
T
A
.
The LT3825E is guaranteed to meet performance specifications from 0°C to
125°C. Specifications over the –40°C to 125°C operating junction temperature
range are assured by design, characterization and correlation with statistical
process controls. Note that the maximum ambient temperature consistent
with these specifications is determined by specific operating conditions in
conjunction with board layout, the rated package thermal resistance and other
environmental factors.
Note 4: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
• 40°C/W)
Note 5: Supply current does not include gate charge current to the
MOSFETs. See Applications Information.
Note 6: Component value range guaranteed by design.
