Datasheet LT1618 (Analog Devices) - 4

LT1618
W U TYPICAL PERFOR A CE CHARACTERISTICS Switching Frequency Frequency Foldback SHDN Pin Current
1.8 1.6 50 TJ = 25°C 1.7 1.4 45 40 TJ = – 50°C 1.6 1.2 A) µ 35 1.5 1.0 VIN = 18V 30 1.4 0.8 25 TJ = 25°C VIN = 1.6V 1.3 0.6 20 15 TJ = 125°C 1.2 0.4 SHDN PIN CURRENT ( SWITCHING FREQUENCY (MHz) SWITCHING FREQUENCY (MHz) 10 1.1 0.2 5 1.0 0 0 – 50 – 25 0 25 50 75 100 125 0 0.2 0.4 0.6 0.8 1.0 1.2 0 5 10 15 20 TEMPERATURE (°C) FEEDBACK PIN VOLTAGE (V) SHUTDOWN PIN VOLTAGE (V) 1618 G07 1618 G08 1618 G09
U U U PIN FUNCTIONS (MS/DD) FB (Pin 1/Pin 1):
Feedback Pin. Set the output voltage by
SW (NA/Pin 6):
Switch Pin for DD Package. Connect this selecting values for R1 and R2 (see Figure 1): pin to Pin 7.
SW (Pin 7/Pin 7):
Switch Pin. This is the collector of the ⎛ V ⎞ R = R OUT 1 2 – 1 internal NPN power switch. Minimize the metal trace area ⎜ ⎟ ⎝ 1. V 263 ⎠ connected to this pin to minimize EMI.
ISN (Pin 2/Pin 2):
Current Sense (–) Pin. The inverting
VIN (Pin 8/Pin 8):
Input Supply Pin. Bypass this pin with input to the current sense amplifier. a capacitor to ground as close to the device as possible.
ISP (Pin 3/Pin 3):
Current Sense (+) Pin. The noninverting
SHDN (Pin 9/Pin 9):
Shutdown Pin. Tie this pin higher input to the current sense amplifier. than 1V to turn on the LT1618; tie below 0.3V to turn it off.
I V ADJ (Pin 4/Pin 4):
Current Sense Adjust Pin. A DC voltage
C (Pin 10/Pin 10):
Compensation Pin for Error Amplifier. applied to this pin will reduce the current sense voltage. If Connect a series RC from this pin to ground. Typical values this adjustment is not needed, tie this pin to ground. are 2kΩ and 10nF.
GND (Pin 5/Pin 5):
Ground Pin. Tie this pin directly to local
Exposed Pad (NA/Pin 11):
The Exposed Pad on the DD ground plane. package is GND and must be soldered to the PCB GND for optimum thermal performance.
NC (Pin 6/NA):
No Connection for MS Package. sn1618 1618fas 4