Datasheet LTC1779 (Analog Devices) - 4

LTC1779
Typical perForMance characTerisTics Reference Voltage Normalized Oscillator Frequency Undervoltage Lockout Trip vs Temperature vs Temperature Voltage vs Temperature
825 15 2.20 VIN = 4.2V VIN = 4.2V VIN FALLING 820 12 2.16 815 9 2.12 810 6 2.08 805 3 2.04 800 0 2.00 VOLTAGE (mV) 795 –3 1.96 V FB 790 –6 TRIP VOLTAGE (V) 1.92 785 NORMALIZED FREQUENCY (%) –9 1.88 780 –12 1.84 775 –15 1.80 –55 –35 –15 5 25 45 65 85 105 125 –55 –35 –15 5 25 45 65 85 105 125 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) 1779 G01 1779 G02 1779 G03
Shutdown Threshold RDS(ON) of Internal P-Channel FET RDS(ON) of Internal P-Channel FET vs Temperature vs Input Voltage vs Temperature
600 1.85 1.85 VIN = 4.2V I I 560 1.70 SW = 100mA SW = 100mA SENSE– = V 1.70 IN SENSE– = VIN 520 1.55 1.55 480 1.40 1.40 VIN = 2.4V 440 1.25 1.25 (Ω) TA = 125°C (Ω) 400 1.10 1.10 VIN = 4.2V 360 V R DS(ON) 0.95 R DS(ON) 0.95 IN = 6V /RUN VOLTAGE (mV) TA = 25°C 320 0.80 0.80 I TH 280 0.65 T 0.65 A = –55°C VIN = 8.4V 240 0.50 0.50 VIN = 9.8V 200 0.35 0.35 –55 –35 –15 5 25 45 65 85 105 125 2 3 4 5 6 7 8 9 10 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) INPUT VOLTAGE (V) TEMPERATURE (°C) 1779 G04 1779 G05 1779 G06
pin FuncTions ITH/RUN (Pin 1):
This pin performs two functions. It serves
SENSE– (Pin 4):
The Negative Input to the Current Com- as the error amplifier compensation point as well as the run parator. Can be connected to VIN for default minimum control input. The current comparator threshold increases peak current of 250mA. Connecting a resistor between with this control voltage. Nominal voltage range for this SENSE– and VIN specifies a lower peak current. (See Ap- pin is 0.7V to 1.9V. Forcing this pin below 0.325V causes plications Information for specifying resistor value.) the device to be shut down. In shutdown all functions are
V
disabled and the internal P-channel MOSFET is turned off.
IN (Pin 5):
Supply Pin. Must be closely decoupled to GND Pin 2. The SW pin will be high impedance.
SW (Pin 6):
Switching Node and Drain of Internal
GND (Pin 2):
Ground Pin. P-Channel Power MOSFET. Connects to external inductor
VFB (Pin 3):
Receives the feedback voltage from an external and catch diode. resistive divider across the output. 1779fa 4 For more information www.linear.com/LTC1779