Datasheet LT1939 (Analog Devices) - 6
| Manufacturer | Analog Devices |
| Description | Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller |
| Pages / Page | 24 / 6 — TYPICAL PERFORMANCE CHARACTERISTICS. Minimum Boost Voltages vs. Boost … |
| File Format / Size | PDF / 358 Kb |
| Document Language | English |
TYPICAL PERFORMANCE CHARACTERISTICS. Minimum Boost Voltages vs. Boost Current vs Switch Current. Temperature
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LT1939
TYPICAL PERFORMANCE CHARACTERISTICS Minimum Boost Voltages vs Boost Current vs Switch Current Temperature Minimum Input Voltage
50 2.7 8 45 7 2.5 40 150°C 6 V 35 OUT1 = 5V –50°C 2.3 5 30 VOUT1 = 3.3V 25 2.1 4 MINIMUM BOOST FOR 20 SWITCH SATURATION 3 25°C 1.9 INPUT VOLTAGE (V) BOOST CURRENT (mA) 15 BOOST VOLTAGE (V) 2 10 1.7 1 5 FSW = 1MHz L = 3.3μH 0 1.5 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 –50 –25 0 25 50 75 100 125 150 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 SWITCH CURRENT (A) TEMPERATURE (°C) LOAD CURRENT (A) 1939 G19 1939 G20 1939 G21
Inductor Value for 2A Maximum LDRV Dropout Voltage vs Load Current (VOUT = 3.3V, Temperature Switcher Dropout Operation IRIPPLE = 250mA)
1.50 6 2500 ILDRV = 5mA IOUT1 = 1A L = 1μH L = 1.5μH 1.45 2250 5 1.40 V 2000 OUT1 = 5V L = 2.2μH 1.35 4 1750 1.30 VOUT1 = 3.3V 1500 1.25 3 1250 L = 3.3μH VOLTAGE (V) 1.20 2 1.15 FREQUENCY (kHz) 1000 OUTPUT VOLTAGE (V) L = 4.7μH 1.10 750 1 L = 6.8μH 1.05 500 L = 10μH 1.00 0 250 –50 –25 0 25 50 75 100 125 150 2.5 3.0 3.5 4.0 4.5 5.0 5.5 5 10 15 20 25 TEMPERATURE (°C) INPUT VOLTAGE (V) INPUT VOLTAGE (V) 1939 G22 1939 G23 1939 G24
PIN FUNCTIONS VIN (Pin 1):
The VIN pin powers the internal control circuitry hysteresis can be used as an undervoltage lockout, prevent- and is monitored by an undervoltage comparator. The VIN ing the regulator from operating until the input voltage has pin is also connected to the collectors of the internal power reached a predetermined level. Force the SHDN pin above NPN switch and linear output NPN. The VIN pin has high its threshold or let it fl oat for normal operation. dI/dt edges and must be decoupled to ground close to
SS (Pin 3):
The SS pin is used to control the slew rate the pin of the device. of the output of both the switching and linear regulators.
SHDN (Pin 2):
The SHDN pin is used to shut down the A single capacitor from the SS pin to ground determines LT1939 and reduce quiescent current to a typical value the regulators’ ramp rate. For soft-start details see the of 12μA. The accurate 0.76V threshold and input current Applications Information section. 1939f 6
TYPICAL PERFORMANCE CHARACTERISTICS Minimum Boost Voltages vs Boost Current vs Switch Current Temperature Minimum Input Voltage
50 2.7 8 45 7 2.5 40 150°C 6 V 35 OUT1 = 5V –50°C 2.3 5 30 VOUT1 = 3.3V 25 2.1 4 MINIMUM BOOST FOR 20 SWITCH SATURATION 3 25°C 1.9 INPUT VOLTAGE (V) BOOST CURRENT (mA) 15 BOOST VOLTAGE (V) 2 10 1.7 1 5 FSW = 1MHz L = 3.3μH 0 1.5 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 –50 –25 0 25 50 75 100 125 150 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 SWITCH CURRENT (A) TEMPERATURE (°C) LOAD CURRENT (A) 1939 G19 1939 G20 1939 G21
Inductor Value for 2A Maximum LDRV Dropout Voltage vs Load Current (VOUT = 3.3V, Temperature Switcher Dropout Operation IRIPPLE = 250mA)
1.50 6 2500 ILDRV = 5mA IOUT1 = 1A L = 1μH L = 1.5μH 1.45 2250 5 1.40 V 2000 OUT1 = 5V L = 2.2μH 1.35 4 1750 1.30 VOUT1 = 3.3V 1500 1.25 3 1250 L = 3.3μH VOLTAGE (V) 1.20 2 1.15 FREQUENCY (kHz) 1000 OUTPUT VOLTAGE (V) L = 4.7μH 1.10 750 1 L = 6.8μH 1.05 500 L = 10μH 1.00 0 250 –50 –25 0 25 50 75 100 125 150 2.5 3.0 3.5 4.0 4.5 5.0 5.5 5 10 15 20 25 TEMPERATURE (°C) INPUT VOLTAGE (V) INPUT VOLTAGE (V) 1939 G22 1939 G23 1939 G24
PIN FUNCTIONS VIN (Pin 1):
The VIN pin powers the internal control circuitry hysteresis can be used as an undervoltage lockout, prevent- and is monitored by an undervoltage comparator. The VIN ing the regulator from operating until the input voltage has pin is also connected to the collectors of the internal power reached a predetermined level. Force the SHDN pin above NPN switch and linear output NPN. The VIN pin has high its threshold or let it fl oat for normal operation. dI/dt edges and must be decoupled to ground close to
SS (Pin 3):
The SS pin is used to control the slew rate the pin of the device. of the output of both the switching and linear regulators.
SHDN (Pin 2):
The SHDN pin is used to shut down the A single capacitor from the SS pin to ground determines LT1939 and reduce quiescent current to a typical value the regulators’ ramp rate. For soft-start details see the of 12μA. The accurate 0.76V threshold and input current Applications Information section. 1939f 6
