Datasheet LT3085 (Analog Devices) - 7

LT3085
TYPICAL PERFORMANCE CHARACTERISTICS Error Amplifi er Gain and Phase Ripple Rejection - SET Pin Current
21 216 150 18 I 144 135 LOAD = 500mA 15 72 120 CSET = 0.1μF 12 0 105 PHASE (deg) 9 –72 I 90 LOAD = 100mA 6 –144 75 CSET = 0 GAIN (dB) I 3 LOAD = 500mA –216 60 0 –288 45 RIPPLE REJECTION (dB) –3 –360 30 RSET = 100k I VIN = VCONTROL = VOUT (NOMINAL) +2V –6 LOAD = 100mA –432 15 RIPPLE = 50mVP–P –9 –504 0 10 100 1k 10k 100k 1M 10 100 1k 10k 100k 1M FREQUENCY (Hz) FREQUENCY (Hz) 3085 G28 3085 G29
PIN FUNCTIONS (DCB/MS8E) VCONTROL (Pin 4/Pin 5):
This pin is the supply pin for the rises with frequency, so include a bypass capacitor in control circuitry of the device. The current fl ow into this battery-powered circuits. A bypass capacitor in the range pin is about 1.7% of the output current. For the device to of 1μF to 10μF suffi ces. regulate, this voltage must be more than 1.2V to 1.35V
NC (NA/Pin 6):
No Connection. The No Connect pin has greater than the output voltage (see VCONTROL Dropout no connection to internal circuitry and may be tied to V Voltage in the Electrical Characteristics table and graphs IN, V in the Typical Performance Characteristics). The LT3085 CONTROL, VOUT, GND, or fl oated. requires a bypass capacitor at V
OUT (Pins 1, 2/Pins 1, 2, 3):
This is the power output CONTROL if more than six inches away from the main input fi lter capacitor. The output of the device. There must be a minimum load current of impedance of a battery rises with frequency, so include 1mA or the output may not regulate. A minimum 2.2μF a bypass capacitor in battery-powered circuits. A bypass output capacitor is required for stability. capacitor in the range of 1μF to 10μF suffi ces.
SET (Pin 3/Pin 4):
This pin is the non-inverting input to the
IN (Pins 5, 6/Pins 7, 8):
This is the collector to the power error amplifi er and the regulation set point for the device. device of the LT3085. The output load current is supplied A fi xed current of 10μA fl ows out of this pin through a through this pin. For the device to regulate, the voltage at single external resistor, which programs the output voltage this pin must be more than 0.1V to 0.5V greater than the of the device. Output voltage range is zero to the absolute output voltage (see V maximum rated output voltage. Transient performance can IN Dropout Voltage in the Electrical Characteristics table and graphs in the Typical Perfor- be improved and output noise can be decreased by adding mance Characteristics). The LT3085 requires a bypass a small capacitor from the SET pin to ground. capacitor at IN if more than six inches away from the main
Exposed Pad (Pin 7/Pin 9):
OUT. Tie directly to Pins 1, 2/ input fi lter capacitor. The output impedance of a battery Pins 2, 3 directly at the PCB. 3085fb 7 Document Outline FEATURES DESCRIPTION APPLICATIONS TYPICAL APPLICATION ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ORDER INFORMATION ELECTRICAL CHARACTERISTICS TYPICAL PERFORMANCE CHARACTERISTICS PIN FUNCTIONS BLOCK DIAGRAM APPLICATIONS INFORMATION TYPICAL APPLICATIONS PACKAGE DESCRIPTION REVISION HISTORY TYPICAL APPLICATION RELATED PARTS