LT1070 Datasheet, PDF (3/12 Pages) Linear Technology – 5A and 2.5A High Efficiency Switching Regulators

LT1070/LT1071
ELECTRICAL CHARACTERISTICS V_IN = 15V, V_C = 0.5V, V_FB = V_REF, output pin open unless otherwise specified.
SYMBOL
V_FB
B_V
V_SAT
I_LIM
∆I_IN
∆I_SW
f
DC (Max)
PARAMETER
Flyback Reference Voltage
Change in Flyback Reference Voltage
Flyback Reference Voltage Line Regulation
Flyback Amplifier Transconductance (g_m)
Flyback Amplifier Source and Sink Current
Output Switch Breakdown Voltage
Output Switch “On” Resistance (Note 4)
Control Voltage to Switch Current
Transconductance
Switch Current Limit (LT1070)
Switch Current Limit (LT1071)
Supply Current Increase During
Switch “On” Time
Switching Frequency
CONDITIONS
I_FB = 50µA
0.05 ≤ I_FB ≤ 1mA
I_FB = 50µA, 3V ≤ V_IN ≤ V_MAX (Note 3)
∆I_C = ±10µA
V_C = 0.6V, I_FB = 50µA (Source)
V_C = 0.6V, I_FB = 50µA (Sink)
3V ≤ V_IN ≤ V_MAX, I_SW = 1.5mA
(LT1070/LT1071)
(LT1070HV/LT1071HV)
LT1070
LT1071
LT1070
LT1071
Duty Cycle ≤ 50%, T_J ≥ 25°C
Duty Cycle ≤ 50%, T_J < 25°C
Duty Cycle = 80% (Note 5)
Duty Cycle ≤ 50%, T_J ≥ 25°C
Duty Cycle ≤ 50%, T_J < 25°C
Duty Cycle = 80% (Note 5)
Maximum Switch Duty Cycle
Flyback Sense Delay Time
Shutdown Mode Supply Current
Shutdown Mode Threshold Voltage
3V ≤ V_IN ≤ V_MAX, V_C = 0.05V
3V ≤ V_IN ≤ V_MAX
MIN TYP MAX
15
q 14
16.3 17.6
18.0
4.5
6.8
8.5
0.01 0.03
150 300 650
q 15
32
70
q 25
40
70
q 65
q 75
q
q
q5
q5
q4
q 2.5
q 2.5
q 2.0
90
90
0.15 0.24
0.30 0.50
8
4
10
11
10
5.0
5.5
5.0
25
35
35
40
45
q 33
47
90
92
97
1.5
100 250
100 150 250
q 50
300
UNITS
V
V
V
%/V
µmho
µA
µA
V
V
Ω
Ω
A/V
A/V
A
A
A
A
A
A
mA/A
kHz
kHz
%
µs
µA
mV
mV
The q denotes the specifications which apply over the full operating
temperature range.
Note 1: Absolute Maximum Ratings are those values beyond which the life of
a device may be impaired.
Note 2: Minimum switch “on” time for the LT1070/LT1071 in current limit is
≈1µs. This limits the maximum input voltage during short-circuit conditions,
in the buck and inverting modes only, to ≈ 35V. Normal (unshorted) conditions
are not affected. Mask changes are being implemented which will reduce
minimum “on” time to ≤ 1µs, increasing maximum short-circuit input voltage
above 40V. If the present LT1070/LT1071 (contact factory for package date
code) is being operated in the buck or inverting mode at high input voltages
and short-circuit conditions are expected, a resistor must be placed in series
with the inductor, as follows:
The value of the resistor is given by:
R
=
t
•
f
• V_IN – V_F
I_LIMIT
–
R_L
t = Minimum “on” time of LT1070/LT1071 in current limit, ≈1µs
f = Operating frequency (40kHz)
V_F = Forward voltage of external catch diode at I_LIMIT
I_LIMIT = Current limit of LT1070 (≈ 8A), LT1071 (≈ 4A)
R_L = Internal series resistance of inductor
Note 3: V_MAX = 55V for LT1070HV and LT1071HV to avoid switch
breakdown.
Note 4: Measured with V_C in hi clamp, V_FB = 0.8V. I_SW = 4A for LT1070
and 2A for LT1071.
Note 5: For duty cycles (DC) between 50% and 80%, minimum
guaranteed switch current is given by I_LIM = 3.33 (2 – DC) for the
LT1070 and I_LIM = 1.67 (2 – DC) for the LT1071.
3