5
LT3473/LT3473A
3473f
Disconnect PNP Quiescent Current
SHDN Voltage to Turn-On
Disconnect PNP
Auxiliary NPN V
BE
CAP VOLTAGE (V)
0
DISCONNECT PNP QUIESCENT CURRENT (µA)
0.8
1.0
1.2
30
3473 G13
0.6
0.4
10 20
535
15 25 40
0.2
0
1.4
OUTPUT CURRENT (mA)
0
0
SHDN VOLTAGE (V)
0.1
0.3
0.4
0.5
40
80
100
0.9
3473 G14
0.2
20 60
0.6
0.7
0.8
TEMPERATURE (°C)
–50
0.50
NPN V
BE
(V)
0.60
0.65
0.70
0.75
0.80
0.85
0
50
3473 G15
0.90
0.95
1.00
I
E
= 1mA
I
E
= 100µA
0.55
100
UU
U
PI FU CTIO S
CAP (Pin 1/Pin 1): Internal Output Voltage. This pin is the
Schottky cathode and disconnect PNP emitter. Connect
output capacitor here.
OUT (Pin 2/Pin 2): Output of Disconnect Circuit. Bypass
this pin with capacitor to ground.
CTRL (Pin 3/Pin 8): External Reference Pin. This pin sets
the FB voltage externally between 0V and 1.25V. Tie this
pin 1.5V or higher to use the internal 1.25V reference.
FB (Pin 4/Pin 7): Feedback Pin. Pin voltage is regulated to
1.25V if internal reference is used or to the CTRL pin
voltage if the CTRL pin voltage is between 0V and 1.25V.
Connect the feedback resistor divider to this pin. The
output voltage is regulated to:
VV
R
R
OUT REF
=+
⎛
⎝
⎜
⎞
⎠
⎟
•
2
1
1
PGOOD (Pin 5/Pin 9): Power Good Output. Open collector
logic output that starts to sink current when FB reaches
within 100mV of the reference voltage.
SHDN (Pin 6/Pin 10): Shutdown Pin. Connect to 1.4V or
higher to enable device; 0.2V or less to disable device. Also
functions as soft-start. Use RC filter as shown in Figure 4.
V
IN
(Pin 7/Pin 11): Input Supply Pin. Must be locally
bypassed with a X5R or X7R type ceramic capacitor.
SW (Pin 8/Pin 12): Switch Pin. Connect inductor here.
Minimize the metal trace area connected to the pin to
minimize EMI.
Exposed Pad (Pin 9/Pin 13): Ground. Solder directly to
PCB ground plane through multiple vias under the pack-
age for optimum thermal performance.
LT3473A Only
NB1 (Pin 3): NPN1 Base.
NE1 (Pin 4): NPN1 Emitter.
NB2 (Pin 5): NPN2 Base.
NE2 (Pin 6): NPN2 Emitter.
(LT3473/LT3473A)
TYPICAL PERFOR A CE CHARACTERISTICS
UW
T
A
= 25°C unless otherwise noted.
