Datasheet

3
LT1248
E
LECTR
IC
AL C CHARA TERIST
ICS
Maximum operating voltage (V
MAX
) = 25V, V
CC
= 18V, R
SET
= 15k to GND, C
SET
= 1nF to GND, I
AC
= 100µA, I
SENSE
= 0V, CA
OUT
= 3.5V,
VA
OUT
= 5V, OVP = 7.5V. No load on any outputs, unless otherwise noted.
I
M
I
AC
(VA
OUT
– 2)
2
The ● denotes specifications which apply over the full operating
temperature range.
Note 1: Multiplier Gain Constant: K =
PARAMETER CONDITIONS MIN TYP MAX UNITS
Current Amplifier
Current Amp Short-Circuit Current CA
OUT
= 0V ● 51430 mA
Input Range, I
SENSE
, M
OUT
(Linear Operation) ● –0.3 1 V
Reference
Reference Output Voltage I
REF
= 0mA, T
A
= 25°C 7.39 7.50 7.60 V
V
REF
Load Regulation –5mA < I
REF
< 0mA 5 mV
V
REF
Line Regulation 11.5V < V
CC
< V
MAX
● –20 5 20 mV
V
REF
Short-Circuit Current V
REF
= 0V ● 12 28 50 mA
V
REF
Worst Case Load, Line, Temperature ● 7.32 7.5 7.68 V
Current Limit
PK
LIM
Offset Voltage ● –15 15 mV
PK
LIM
Input Current PK
LIM
= –0.1V ● –50 –100 µA
PK
LIM
to GTDR Propagation Delay PK
LIM
Falling from 50mV to –50mV 400 ns
Multiplier
Multiplier Output Current I
AC
= 100µA, R
SET
= 15k 35 µA
Multiplier Output Current Offset R
AC
= 1M from I
AC
to GND ● –0.05 –0.5 µA
Multiplier Maximum Output Current I
AC
= 450µA, R
SET
= 15k, VA
OUT
= 7V, M
OUT
= 0V ● –286 –260 –235 µA
Multiplier Gain Constant (Note 1) 0.035 V
–2
I
AC
Input Resistance I
AC
from 50µA to 1mA 15 25 35 kΩ
Oscillator
Oscillator Frequency R
SET
= 15k, C
SET
= 1000pF ● 85 100 115 kHz
R
SET
= 15k, C
SET
= 1500pF ● 58 68 78 kHz
C
SET
Ramp Peak-to-Peak Amplitude 4.35 4.7 5.0 V
C
SET
Ramp Valley Voltage 1.25 1.4 1.55 V
Synchronization Pulse Threshold on EN/SYNC Pin
Pulse Low = 3.5V, High = 7V, Width > 200ns
4.5 5.6 6.5 V
Synchronization Frequency Range
R
SET
= 15k, C
SET
= 1000pF
● 1.2 1.6 f
NOM
Overvoltage Comparator
Comparator Trip Voltage Ratio (V
TRIP
/V
REF
) ● 1.04 1.05 1.06
Hysteresis 0.35 V
OVP Bias Current OVP = 7.5V ● –50 –250 nA
OVP Propagation Delay 100 ns
Gate Driver
Max GTDR Output Voltage 0mA Load, 18V < V
CC
● 12 15 17.5 V
GTDR Output High –200mA Load, 11.5V ≤ V
CC
≤ 15V ● V
CC
– 3.0 V
GTDR Output Low (Device Unpowered) V
CC
= 0V, 50mA Load (Sinking) ● 0.9 1.5 V
GTDR Output Low (Device Active) 200mA Load (Sinking) ● 0.5 1 V
10mA Load ● 0.2 0.4 V
Peak GTDR Current 10nF from GTDR to GND 2 A
GTDR Rise and Fall Time 1nF from GTDR to GND 25 ns
GTDR Max Duty Cycle 90 96 %