Datasheet LT3500 (Analog Devices) - 7
| Fabricante | Analog Devices |
| Descripción | Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller |
| Páginas / Página | 28 / 7 — TYPICAL PERFORMANCE CHARACTERISTICS. Inductor Value for 2A Maximum. LDRV … |
| Formato / tamaño de archivo | PDF / 331 Kb |
| Idioma del documento | Inglés |
TYPICAL PERFORMANCE CHARACTERISTICS. Inductor Value for 2A Maximum. LDRV Dropout Voltage. Load Current (VOUT1 = 3.3V,
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LT3500
TYPICAL PERFORMANCE CHARACTERISTICS Inductor Value for 2A Maximum LDRV Dropout Voltage Load Current (VOUT1 = 3.3V, vs Temperature Switcher Dropout Operation IRIPPLE = 250mA)
1.50 6 2500 ILDRV = 5mA IVOUT1 = 1A TA = 25°C 1.45 TA = 25°C 2250 5 L = 2.2μH L = 1μH 1.40 V 2000 VOUT1 = 5V 1.35 L = 1.5μH 4 1750 1.30 VVOUT1 = 3.3V 1500 L = 3.3μH 1.25 3 1250 VOLTAGE (V) 1.20 2 L = 4.7μH 1.15 1000 OUTPUT VOLTAGE (V) FREQUENCY (kHz) 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 30 35 40 TEMPERATURE (°C) INPUT VOLTAGE (V) INPUT VOLTAGE (V) 3500 G22 3500 G23 3500 G24
PIN FUNCTIONS VIN:
The VIN pin powers the internal control circuitry and nominal regulating voltage. For VIN above 2V, its output is monitored by an undervoltage comparator. The VIN pin state remains true, although during SHDN, VIN undervoltage is also connected to the collectors of the internal power lockout, or thermal shutdown, its current sink capability NPN switch and linear output NPN. The VIN pin has high is reduced dI/dt edges and must be decoupled to ground close to
V
the pin of the device.
C:
The VC pin is the output of the error amplifi er and the input to the peak switch current comparator. It is normally
SHDN:
The SHDN pin is used to shut down the LT3500 used for frequency compensation, but can also be used and reduce quiescent current to a typical value of as a current clamp or control loop override. If the error 12μA. The accurate 0.76V threshold and input current amplifi er drives VC above the maximum switch current hysteresis can be used as an undervoltage lockout, prevent- level, a voltage clamp activates. This indicates that the ing the regulator from operating until the input voltage has output is overloaded and current to be pulled from the reached a predetermined level. Force the SHDN pin above SS pin reducing the regulation point. its threshold or let it fl oat for normal operation.
RT/SYNC:
This RT/SYNC pin provides two modes of setting
SS:
The SS pin is used to control the slew rate of the the constant switch frequency. output of both the switching and linear regulators. A Connecting a resistor from the R single capacitor from the SS pin to ground determines T/SYNC pin to ground will set the R the regulators’ ramp rate. For soft-start details see the T/SYNC pin to a typical value of 1V. The resultant switching frequency will be set by the resistor Applications Information section. value. The minimum value of 15kΩ and maximum value
PG:
The power good pin is an open-collector output that of 200kΩ set the switching frequency to 2.5MHz and sinks current when the FB or LFB falls below 90% of its 250kHz respectively. 3500fc 7
TYPICAL PERFORMANCE CHARACTERISTICS Inductor Value for 2A Maximum LDRV Dropout Voltage Load Current (VOUT1 = 3.3V, vs Temperature Switcher Dropout Operation IRIPPLE = 250mA)
1.50 6 2500 ILDRV = 5mA IVOUT1 = 1A TA = 25°C 1.45 TA = 25°C 2250 5 L = 2.2μH L = 1μH 1.40 V 2000 VOUT1 = 5V 1.35 L = 1.5μH 4 1750 1.30 VVOUT1 = 3.3V 1500 L = 3.3μH 1.25 3 1250 VOLTAGE (V) 1.20 2 L = 4.7μH 1.15 1000 OUTPUT VOLTAGE (V) FREQUENCY (kHz) 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 30 35 40 TEMPERATURE (°C) INPUT VOLTAGE (V) INPUT VOLTAGE (V) 3500 G22 3500 G23 3500 G24
PIN FUNCTIONS VIN:
The VIN pin powers the internal control circuitry and nominal regulating voltage. For VIN above 2V, its output is monitored by an undervoltage comparator. The VIN pin state remains true, although during SHDN, VIN undervoltage is also connected to the collectors of the internal power lockout, or thermal shutdown, its current sink capability NPN switch and linear output NPN. The VIN pin has high is reduced dI/dt edges and must be decoupled to ground close to
V
the pin of the device.
C:
The VC pin is the output of the error amplifi er and the input to the peak switch current comparator. It is normally
SHDN:
The SHDN pin is used to shut down the LT3500 used for frequency compensation, but can also be used and reduce quiescent current to a typical value of as a current clamp or control loop override. If the error 12μA. The accurate 0.76V threshold and input current amplifi er drives VC above the maximum switch current hysteresis can be used as an undervoltage lockout, prevent- level, a voltage clamp activates. This indicates that the ing the regulator from operating until the input voltage has output is overloaded and current to be pulled from the reached a predetermined level. Force the SHDN pin above SS pin reducing the regulation point. its threshold or let it fl oat for normal operation.
RT/SYNC:
This RT/SYNC pin provides two modes of setting
SS:
The SS pin is used to control the slew rate of the the constant switch frequency. output of both the switching and linear regulators. A Connecting a resistor from the R single capacitor from the SS pin to ground determines T/SYNC pin to ground will set the R the regulators’ ramp rate. For soft-start details see the T/SYNC pin to a typical value of 1V. The resultant switching frequency will be set by the resistor Applications Information section. value. The minimum value of 15kΩ and maximum value
PG:
The power good pin is an open-collector output that of 200kΩ set the switching frequency to 2.5MHz and sinks current when the FB or LFB falls below 90% of its 250kHz respectively. 3500fc 7