LT1076HVCT Linear Technology, LT1076HVCT Datasheet - Page 10

• Manufacturer Part Number: LT1076HVCT
• Description: IC SWTCHNG REG STP-DWN 2A TO-220
• Manufacturer: Linear Technology
• Type: Step-Down (Buck), Step-Up (Boost), Inverting, Flybackr

Specifications of LT1076HVCT

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 2.5 ~ 50 V
• Current - Output: 2A
• Frequency - Switching: 100kHz
• Voltage - Input: 8 ~ 64 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Through Hole
• Package / Case: TO-220-5 (Bent and Staggered Leads)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

SHUTDOWN
LT1074/LT1076
PI
Undervoltage Lockout
Undervoltage lockout point is set by R1 and R2 in Figure 6.
To avoid errors due to the 10µA shutdown pin current, R2
is usually set at 5k, and R1 is found from:
If quiescent supply current is critical, R2 may be increased
up to 15kΩ, but the denominator in the formula for R2
should replace V
10
V
V
R
U
TP
SH
1
PIN
=
DESCRIPTIO S
= Desired undervoltage lockout voltage
10 A
= Threshold for lockout on the
R
µ
2
shutdown pin = 2.45V
(
V
TP
2.3V
0.3V
Figure 6. Undervoltage Lockout
V
Figure 5. Shutdown Circuitry
−
SH
R1
R2
SH
5k
V
SH
with V
–
+
–
+
)
C1
C2
SH
U
– (10µA)(R2).
300 A
SHUT
µ
LT1074
GND
V
IN
Q1
TO TOTAL
REGULATOR
SHUTDOWN
LT1074•PD08
V
LT1074•PD07
IN
I
PIN
6V
LIM
EXTERNAL
C
LIM
Hysteresis in undervoltage lockout may be accomplished
by connecting a resistor (R3) from the I
shutdown pin as shown in Figure 7. D1 prevents the
shutdown divider from altering current limit.
If R3 is added, the lower trip point (V
the same. The upper trip point (V
If R1 and R2 are chosen, R3 is given by:
Example: An undervoltage lockout is required such that
the output will not start until V
to operate until V
R
R
R
Trip Po
V
UTP
1
3
3
=
=
=
(
=
V
20 2 35 1
2 34
(
UTP
.
*1N4148
(
int
V
2 35 0 8 12 5
V
−
SH
.
SH
k
=
R1
R2
−
⎛
⎜
⎝
)
.
1
−
−
(
Figure 7. Adding Hysteresis
V
V
R3
15
R
IN
R
TP
SH
0 8
⎛
⎜
⎝
2
1
.
.
V
drops to 15V. Let R2 = 2.32k.
⎛
⎜
⎝
2 35
=
+
V R
+
)( )
1
−
.
D1*
)( )
2 35
R
+
R
12 5
2 32
2 35
.
3
1
.
V
R
.
R
.
1
⎞
⎟ −
⎠
.
2
1
V
⎞
⎟
⎠
SHUT
V
⎞
⎟
⎠
I
LIM
⎛
⎜
⎝
0 8
)
=
1
IN
.
=
+
LT1074
OPTIONAL CURRENT
LIMIT RESISTOR
3 9
V
= 20V, but will continue
UTP
12 5
.
V
R
R
⎛
⎜
⎝
IN
IN
1
2
k
R
R
.
) will be:
⎞
⎟
⎠
descending) will be
3
1
k
⎞
⎟
⎠
LT1074•PD09
LIM
pin to the
sn1074 1074fds