LT1768I データシートの表示（PDF） - Linear Technology
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LT1768I Datasheet PDF : 20 Pages
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LT1768
ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VVIN = 12V, IDIO1/2 = 250µA, VPROG = 0V, VPWM = 2.5V, IRMAX = –100µA,
IRMIN = –100µA, unless otherwise specified.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
IPWM
VDIO1/2
VVCCLAMP
ISENSE
VSENSE
PWM Input Bias Current
q
0.6
4
µA
PWM Duty Cycle
PWM Frequency
VPROG = 1.75
CT = 0.22µF (Note 7)
45
50
55
%
90
110 130
Hz
DIO1/2 Positive Voltage
DIO1/2 Negative Voltage
VC High Clamp Voltage
VC Switching Threshold
SENSE Input Bias Current
IDIO = 14mA
IDIO = –14mA
VPROG = 4.5V (Note 8)
VPROG = 4.5V (Note 8)
VSENSE = 0V
1.7
1.9
V
–1.1 –1.3
V
3.6
3.7
3.9
V
0.5
0.7 0.95
V
–25 –30
µA
SENSE Threshold for Current Limit
VVC = VVCCLAMP, Duty Cycle < 50%, VPROG = 1V
85
100 115
mV
VVC = VVCCLAMP, Duty Cycle 80%, VPROG = 1V
90
mV
IDIO1/2 to IRMAX Ratio
VPROG = 4.5V (Note 5)
q 94
98
104
A/A
VPROG = 4.5V, IDIO1 or IDIO2 = 0, VVC = 2.5V,
(Note 5)
45
49
55
A/A
IDIO1/2 to IRMIN Ratio
VPROG < 0.75V (Note 6)
q9
10
11
A/A
VPROG < 0.75V, IDIO1 or IDIO2 = 0, VVC = 2.5V,
(Note 6)
9
10
11
A/A
IGATE
GATE Drive Peak Source Current
GATE Drive Peak Sink Current
1.5
A
1.5
A
GATE Drive Saturation Voltage
VVIN = 12V, IGATE = –100mA, VPROG = 4.5V
q 9.8
10.2
V
GATE Drive Clamp Voltage
VVIN = 24V, IGATE = –10mA, VPROG = 4.5V
q
12.5
14
V
GATE Drive Low Saturation Voltage
IGATE = 100mA
q
0.4
0.6
V
Open LAMP Threshold
(Note 9)
100 125 150
µA
FAULT Pin Saturation Voltage
IFAULT = 1mA, IDI01, IDI02 = 0µA, VPROG = 4.5V
0.2
0.3
V
FAULT Pin Leakage Current
VFAULT = 5V
20
100
nA
Thermal ShutdownTemperature
160
°C
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: This is the threshold voltage where the lamp current switches
from zero current to minimum lamp current. For VPROG less than the
threshold voltage, lamp current will be at zero. For VPROG greater than the
threshold voltage, lamp current will be equal to the minimum lamp
current. Minimum lamp current is set by the value of the resistor from the
RMIN pin to ground. See Applications Information for more details.
Note 3: This is the threshold voltage where the device starts to pulse width
modulate the lamp current. For VPROG less than the threshold voltage,
lamp current will be equal to the minimum lamp current. For VPROG
greater than the threshold voltage, lamp current will be pulse width
modulated between the minimum lamp current and some higher value.
Minimum lamp current is set by the value of the resistor from the RMIN pin
to ground. The higher value lamp current is a function of the RMAX resistor
to ground value, and the voltages on the PWM and PROG pins. See
Applications Information for more details.
Note 4: This is the threshold voltage where the lamp current reaches its
maximum value. For VPROG greater than the threshold voltage, there will
be no increase in lamp current. For VPROG less than the threshold voltage,
lamp current will be at some lower value. Maximum lamp current is set by
the value of the resistor from the RMAX pin to ground. The lower value
lamp current is a function of the RMIN and RMAX resistors, and the
voltages on the PWM and PROG pins. See Applications Information for
more details.
Note 5: IDIO1/2 to IRMAX ratio is determined by setting IRMAX to –100µA,
VPROG to 4.5V, VVC to 2.5V, and then ramping a DC current out of the
DIO1/2 pins from zero until the DC current in the VC voltage source
current equals zero. The IDIO1/2 to IRMAX ratio is then defined as (IDIO1 +
IDIO2)/IRMAX. See Applications Information for more details.
Note 6: IDIO1/2 to IRMIN ratio is determined by setting IRMIN to –100µA,
VPROG to 0.75V, VVC to 2.5V, and then ramping a DC current out of the
DIO1/2 pins from zero until the DC current in the VC voltage source
current equals zero. The IDIO1/2 to IRMIN ratio is then defined as (IDIO1 +
IDIO2)/IRMIN. See Applications Information for more details.
Note 7: The PWM frequency is set by the equation PWMFREQ = 22Hz/
CT(µF).
Note 8: For VC voltages less than the switching threshold, GATE switching
is disabled.
Note 9: An open lamp will be detected if either IDIO1 or IDIO2 is less than
the threshold current for at least 1 full PWM cycle.
3
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