LT3580
TYPICAL PERFORMANCE CHARACTERISTICS
SHDN
Pin Current
30
25
SHDN
PIN CURRENT (μA)
SHDN
PIN CURRENT (μA)
20
15
10
5
100°C
0
0
0.5
1
1.5
SHDN
VOLTAGE (V)
2
3580 G10
T
A
= 25°C unless otherwise specified
Active/Lockout Threshold
1.40
1.38
SHDN
Pin Current
300
–50°C
250
200
150
100
50
0
0
5
20
15
25
10
SHDN
VOLTAGE (V)
30
3580 G11
20°C
SHDN
VOLTAGE (V)
100°C
1.36
1.34
1.32
1.30
1.28
1.26
1.24
1.22
SHDN
FALLING
SHDN
RISING
–50°C
20°C
1.20
–50
50
0
TEMPERATURE (°C)
100
3580 G12
PIN FUNCTIONS
FB (Pin 1):
Positive and Negative Feedback Pin. For a
boost or inverting converter, tie a resistor from the FB pin
to V
OUT
according to the following equations:
R
FB
=
R
FB
=
RT (Pin 6):
Timing Resistor Pin. Adjusts the switching
frequency. Place a resistor from this pin to ground to set
the frequency to a fixed free running level. Do not float
this pin.
SS (Pin 7):
Soft-Start Pin. Place a soft-start capacitor here.
Upon start-up, the SS pin will be charged by a (nominally)
275k resistor to about 2.2V.
SYNC (Pin 8):
To synchronize the switching frequency to
an outside clock, simply drive this pin with a clock. The
high voltage level of the clock needs to exceed 1.3V, and
the low level should be less 0.4V. Drive this pin to less than
0.4V to revert to the internal free running clock. See the
Applications Information section for more information.
Exposed Pad (Pin 9):
Ground. Must be soldered directly
to local ground plane.
(
V
OUT
1.215
)
6
(
83.3 • 10
V
OUT
+
5mV
83.3 • 10
6
; Boost or SEPIC Converter
)
; Inverting Converter
VC (Pin 2):
Error Amplifier Output Pin. Tie external com-
pensation network to this pin.
V
IN
(Pin 3):
Input Supply Pin. Must be locally bypassed.
SW (Pin 4):
Switch Pin. This is the collector of the internal
NPN Power switch. Minimize the metal trace area con-
nected to this pin to minimize EMI.
SHDN
(Pin 5):
Shutdown Pin. In conjunction with the
UVLO (undervoltage lockout) circuit, this pin is used
to enable/disable the chip and restart the soft-start
sequence. Drive below 1.24V to disable the chip. Drive
above 1.38V to activate chip and restart the soft-start
sequence. Do not float this pin.
3580fc
5
LINER [ LINEAR TECHNOLOGY ]
