LT1573 Linear Technology Corporation, LT1573 Datasheet
LT1573
Available stocks
Related parts for LT1573
LT1573 Summary of contents
Page 1
... This greatly reduces bulk storage capacitance when the regulator is used in applications with fast, high current load transients. To keep cost and complexity low, the LT1573 uses a new time-delayed latching overcurrent protection technique that requires no external current sense resistor. Base drive ...
Page 2
... Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec.)................ 300°C ELECTRICAL CHARACTERISTICS range, otherwise specifications are at T PARAMETER DC Characteristics LT1573 Reference Voltage (Adjustable)(Note 2) LT1573-3.3 Output Voltage (Note 2) LT1573-2.8 Output Voltage (Note 2) LT1573-2.5 Output Voltage (Note 2) Line Regulation LT1573 ( LT1573-3 OUT LT1573-2 ...
Page 3
... Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: Operating conditions are limited by maximum junction temperature. The regulated feedback or output voltage specification will W U TYPICAL PERFOR A CE CHARACTERISTICS LT1573 Feedback Pin Voltage vs Temperature 1.290 1.285 1.280 1.275 1.270 1 ...
Page 4
... LT1573 W U TYPICAL PERFOR A CE CHARACTERISTICS Drive Pin Current vs Feedback Pin Voltage 450 T = 130°C J 400 350 T = 25°C J 300 T = –45°C J 250 200 150 100 0.2 0.4 0.6 0.8 1.4 1.0 1.2 FEEDBACK PIN VOLTAGE (V) 1573 G07 Latch Pin Latch-Off Threshold vs Input Voltage 3.0 2 25° –45° ...
Page 5
... PNP output transistor. A resistor is normally inserted between the base of the external PNP output transistor and the DRIVE pin. This resistor is sized to allow the LT1573 to sink the appropriate amount of base current for a given application and to activate the overcurrent latch in a fault condition ...
Page 6
... SHUTDOWN CTIO AL DESCRIPTIO The basic block diagram of the LT1573 is shown above. The regulating loop consists of a 1.265V reference, an error amplifier, a Darlington driver and an external PNP pass transistor. The 1.265V reference feeds the noninvert- ing input of the error amplifier. The error amplifier drives the Darlington connected transistor pair Q1 and Q2 ...
Page 7
... U U APPLICATIO S I FOR ATIO The LT1573 is designed to be used in conjunction with an external PNP transistor. The overall specifications of a regulator circuit using the LT1573 and an external PNP will be heavily dependent on the specifications of the external PNP. While there are a wide variety of PNP transistors ...
Page 8
... PNP transistor when it is driven with a base current equal to the available drive current of the LT1573. The LT1573 is guaranteed to sink 250mA of base current (440mA typ). The available drive current of the LT1573 can be reduced by adding a resistor (R D with the DRIVE pin. Table 1 lists some useful operating points for the D45H11 ...
Page 9
... R is included in the circuit for the overcurrent protection D latch-off function. There is a minimum value for this resistance calculated by Equation 1 with the drive current I DRIVE (= 250mA) from the LT1573. At high currents ° C limits the power dissipation in the LT1573. In some BE ...
Page 10
... Power Dissipation of the LT1573: The worst-case power dissipation in the LT1573 is a function of drive current, supply voltage and the value of R dissipation for the LT1573 occurs when the drive cur- rent is equal to approximately one half of its maximum value ...
Page 11
... Output Capacitor The LT1573 is designed to be used with an external PNP transistor with a high gain-bandwidth product f a regulator with a very fast transient response, which can minimize the size of the output capacitor. For a regulator made of an LT1573 and a D45H11, only one 10µ ...
Page 12
... In the specific example drawn in Figure 3 with two output transistors, the resistance of R resistance twice the value of the resistance case of n PNP transistors in parallel, the resistance COMP V OUT LT1573 DRIVE Q OUT1 ...
Page 13
... FOR T > 45°C, C PLACE C OUT1 220µF SURFACE MOUNT TANTALUM CAPACITOR IN OUT2 C = 0.5µF FOR 100ms TIME OUT AT ROOM TEMPERATURE TIME SHDN (ACTIVE HIGH) PIN SHOULD BE TIED TO GROUND NOT USED W U Table 4. LT1573 Output Feedback Divider Resistance in parallel ..., OUTPUT D1 D2 VOLTAGE (V) 1.5 1.8 2.0 2.2 2.5 2 ...
Page 14
... COMP V OUT 39Ω 200Ω Q 1/2W 1/8W OUT DRIVE MOTOROLA D45H11 + + + OUT1 OUT2 5V/2A Output from Wall Adapter Input LT1573 FB COMP LATCH V OUT SHDN 130Ω 200Ω 1/2W 1/8W MOTOROLA DRIVE GND D45H11 + + C C OUT IN V OUT 2 ...
Page 15
... MOTOROLA DRIVE D45H11 + + C C OUT IN LT1573 COMP V OUT 6Ω 200Ω 1/2W 1/8W MOTOROLA DRIVE D45H11 + + C C IN2 OUT LT1573 V OUT 2.85V R1 1.24k 1/8W LOAD R2 1k 1/8W GND 1573 TA04 V IN1 2. IN1 V OUT 1.5V R1 186Ω 1/8W LOAD R2 1k 1/8W GND 1573 TA05 sn1573 1573fas ...
Page 16
... Low Dropout, Fast Response Regulators LT1761/LT1762/LT1763 Low Noise LDO Micropower Regulators LT1764 3A Fast Transient Response Low Dropout Regulator Linear Technology Corporation 16 1630 McCarthy Blvd., Milpitas, CA 95035-7417 FAX: (408) 434-0507 TELEX: 499-3977 ● LT1573 COMP V OUT 6.2Ω 200Ω ...