Datasheet LT3007 (Analog Devices) - 10
| Manufacturer | Analog Devices |
| Description | 3μA IQ, 20mA, 45V Low Dropout Fault Tolerant Linear Regulators |
| Pages / Page | 20 / 10 — APPLICATIONS INFORMATION. Table 1. Output Voltage Resistor Divider … |
| File Format / Size | PDF / 344 Kb |
| Document Language | English |
APPLICATIONS INFORMATION. Table 1. Output Voltage Resistor Divider Values. VOUT. Adjustable Operation
Model Line for this Datasheet
- LT3007ETS8#PBF LT3007ETS8#TRMPBF LT3007ETS8#TRPBF LT3007ETS8-1.2#PBF LT3007ETS8-1.2#TRMPBF LT3007ETS8-1.2#TRPBF LT3007ETS8-1.5#PBF LT3007ETS8-1.5#TRMPBF LT3007ETS8-1.5#TRPBF LT3007ETS8-1.8#PBF LT3007ETS8-1.8#TRMPBF LT3007ETS8-1.8#TRPBF LT3007ETS8-2.5#PBF LT3007ETS8-2.5#TRMPBF LT3007ETS8-2.5#TRPBF LT3007ETS8-3.3#PBF LT3007ETS8-3.3#TRMPBF LT3007ETS8-3.3#TRPBF LT3007ETS8-5#PBF LT3007ETS8-5#TRMPBF LT3007ETS8-5#TRPBF LT3007HTS8#PBF LT3007HTS8#TRMPBF LT3007HTS8#TRPBF LT3007ITS8#PBF LT3007ITS8#TRMPBF LT3007ITS8#TRPBF LT3007ITS8-1.2#PBF LT3007ITS8-1.2#TRMPBF LT3007ITS8-1.2#TRPBF LT3007ITS8-1.5#PBF LT3007ITS8-1.5#TRMPBF LT3007ITS8-1.5#TRPBF LT3007ITS8-1.8#PBF LT3007ITS8-1.8#TRMPBF LT3007ITS8-1.8#TRPBF LT3007ITS8-2.5#PBF LT3007ITS8-2.5#TRMPBF LT3007ITS8-2.5#TRPBF LT3007ITS8-3.3#PBF LT3007ITS8-3.3#TRMPBF LT3007ITS8-3.3#TRPBF LT3007ITS8-5#PBF LT3007ITS8-5#TRMPBF LT3007ITS8-5#TRPBF
- LT3007ETS8#TRMPBF LT3007ETS8#TRPBF LT3007ETS8-1.2#TRMPBF LT3007ETS8-1.2#TRPBF LT3007ETS8-1.5#TRMPBF LT3007ETS8-1.5#TRPBF LT3007ETS8-1.8#TRMPBF LT3007ETS8-1.8#TRPBF LT3007ETS8-2.5#TRMPBF LT3007ETS8-2.5#TRPBF LT3007ETS8-3.3#TRMPBF LT3007ETS8-3.3#TRPBF LT3007ETS8-5#TRMPBF LT3007ETS8-5#TRPBF LT3007HTS8#TRMPBF LT3007HTS8#TRPBF LT3007ITS8#TRMPBF LT3007ITS8#TRPBF LT3007ITS8-1.2#TRMPBF LT3007ITS8-1.2#TRPBF LT3007ITS8-1.5#TRMPBF LT3007ITS8-1.5#TRPBF LT3007ITS8-1.8#TRMPBF LT3007ITS8-1.8#TRPBF LT3007ITS8-2.5#TRMPBF LT3007ITS8-2.5#TRPBF LT3007ITS8-3.3#TRMPBF LT3007ITS8-3.3#TRPBF LT3007ITS8-5#TRMPBF LT3007ITS8-5#TRPBF
Text Version of Document
LT3007 Series
APPLICATIONS INFORMATION
The LT3007 is a low dropout linear regulator with ultra- and the divider current is zero. Curves of ADJ Pin Voltage vs low quiescent current and shutdown. Quiescent current is Temperature and ADJ Pin Bias Current vs Temperature appear extremely low at 3µA and drops well below 1µA in shut- in the Typical Performance Characteristics. down. The device supplies up to 20mA of output current. Specifications for output voltages greater than 0.6V are Dropout voltage at 20mA is typically 300mV. The LT3007 proportional to the ratio of the desired output voltage to incorporates several protection features, making it ideal for 0.6V: V use in battery-powered systems. The device protects itself OUT/0.6V. For example, load regulation for an output current change of 100µA to 20mA is –0.5mV typical at against both reverse-input and reverse-output voltages. V In battery backup applications, where a backup battery OUT = 0.6V. At VOUT = 5V, load regulation is: holds up the output when the input is pulled to ground, 5V •(−0.5mV)=−4.17mV the LT3007 acts as if a blocking diode is in series with its 0.6V output and prevents reverse current flow. In applications where the regulator load returns to a negative supply, the Table 1 shows resistor divider values for some common output can be pulled below ground by as much as 50V output voltages with a resistor divider current of about 1µA. without affecting start-up or normal operation.
Table 1. Output Voltage Resistor Divider Values
Care must be taken when designing LT3007 applications
VOUT R1 R2
to operate at temperatures greater than 125°C. See the 1V 604k 402k High Temperature Operation Section for more information. 1.2V 590k 590k 1.5V 590k 887k
Adjustable Operation
1.8V 590k 1.18M The LT3007 has an output voltage range of 0.6V to 44.5V. 2.5V 590k 1.87M Figure 2 shows that output voltage is set by the ratio of two 3V 590k 2.37M external resistors. The IC regulates the output to maintain the 3.3V 619k 2.8M ADJ pin voltage at 600mV referenced to ground. The current 5V 590k 4.32M in R1 equals 600mV/R1 and the current in R2 is the current in R1 minus the ADJ pin bias current. The ADJ pin bias cur-
Because the ADJ pin is relatively high impedance (de-
rent, typically 400pA at 25°C, flows out of the pin. Calculate
pending on the resistor divider used), stray capacitances
the output voltage using the formula in Figure 2. An R1 value
at this pin should be minimized. Special attention should
of 619k sets the divider current to 0.97µA. Do not make R1’s
be given to any stray capacitances that can couple ex-
value any greater than 619k to minimize output voltage errors
ternal signals onto the ADJ pin, producing undesirable
due to the ADJ pin bias current and to insure stability under
output transients or ripple.
minimum load conditions. In shutdown, the output turns off
Extra care should be taken in assembly when using high valued resistors. Small amounts of board contamination
IN OUT VOUT
can lead to significant shifts in output voltage. Appropriate
VIN LT3007
post-assembly board cleaning measures should be
R2
implemented to prevent board contamination. If the
SHDN ADJ
board is to be subjected to humidity cycling or if board
GND R1 3007 F02
cleaning measures cannot be guaranteed, consideration should be given to using resistors an order of magnitude
VOUT = 600mV • (1 + R2/R1) – (IADJ • R2)
smaller than in Table 1 to prevent contamination from
VADJ = 600mV
causing unwanted shifts in the output voltage. A fixed
IADJ = 0.4nA at 25°C OUTPUT RANGE = 0.6V to 44.5V
voltage option in the LT3007 series does not need these Figure 2. Adjustable Operation special considerations.
3007fa 10 For more information www.linear.com/LT3007
APPLICATIONS INFORMATION
The LT3007 is a low dropout linear regulator with ultra- and the divider current is zero. Curves of ADJ Pin Voltage vs low quiescent current and shutdown. Quiescent current is Temperature and ADJ Pin Bias Current vs Temperature appear extremely low at 3µA and drops well below 1µA in shut- in the Typical Performance Characteristics. down. The device supplies up to 20mA of output current. Specifications for output voltages greater than 0.6V are Dropout voltage at 20mA is typically 300mV. The LT3007 proportional to the ratio of the desired output voltage to incorporates several protection features, making it ideal for 0.6V: V use in battery-powered systems. The device protects itself OUT/0.6V. For example, load regulation for an output current change of 100µA to 20mA is –0.5mV typical at against both reverse-input and reverse-output voltages. V In battery backup applications, where a backup battery OUT = 0.6V. At VOUT = 5V, load regulation is: holds up the output when the input is pulled to ground, 5V •(−0.5mV)=−4.17mV the LT3007 acts as if a blocking diode is in series with its 0.6V output and prevents reverse current flow. In applications where the regulator load returns to a negative supply, the Table 1 shows resistor divider values for some common output can be pulled below ground by as much as 50V output voltages with a resistor divider current of about 1µA. without affecting start-up or normal operation.
Table 1. Output Voltage Resistor Divider Values
Care must be taken when designing LT3007 applications
VOUT R1 R2
to operate at temperatures greater than 125°C. See the 1V 604k 402k High Temperature Operation Section for more information. 1.2V 590k 590k 1.5V 590k 887k
Adjustable Operation
1.8V 590k 1.18M The LT3007 has an output voltage range of 0.6V to 44.5V. 2.5V 590k 1.87M Figure 2 shows that output voltage is set by the ratio of two 3V 590k 2.37M external resistors. The IC regulates the output to maintain the 3.3V 619k 2.8M ADJ pin voltage at 600mV referenced to ground. The current 5V 590k 4.32M in R1 equals 600mV/R1 and the current in R2 is the current in R1 minus the ADJ pin bias current. The ADJ pin bias cur-
Because the ADJ pin is relatively high impedance (de-
rent, typically 400pA at 25°C, flows out of the pin. Calculate
pending on the resistor divider used), stray capacitances
the output voltage using the formula in Figure 2. An R1 value
at this pin should be minimized. Special attention should
of 619k sets the divider current to 0.97µA. Do not make R1’s
be given to any stray capacitances that can couple ex-
value any greater than 619k to minimize output voltage errors
ternal signals onto the ADJ pin, producing undesirable
due to the ADJ pin bias current and to insure stability under
output transients or ripple.
minimum load conditions. In shutdown, the output turns off
Extra care should be taken in assembly when using high valued resistors. Small amounts of board contamination
IN OUT VOUT
can lead to significant shifts in output voltage. Appropriate
VIN LT3007
post-assembly board cleaning measures should be
R2
implemented to prevent board contamination. If the
SHDN ADJ
board is to be subjected to humidity cycling or if board
GND R1 3007 F02
cleaning measures cannot be guaranteed, consideration should be given to using resistors an order of magnitude
VOUT = 600mV • (1 + R2/R1) – (IADJ • R2)
smaller than in Table 1 to prevent contamination from
VADJ = 600mV
causing unwanted shifts in the output voltage. A fixed
IADJ = 0.4nA at 25°C OUTPUT RANGE = 0.6V to 44.5V
voltage option in the LT3007 series does not need these Figure 2. Adjustable Operation special considerations.
3007fa 10 For more information www.linear.com/LT3007
