1.24V Low-Voltage Adjustable Precision Shunt Regulator

Transcription

1 GENERAL DESCRIPTION The L432 is a three-terminal adjustable shunt regulator utilizing an accurate.24v band gap reference. The output voltage can be set to any value between.24v (V REF ) to 8V with two external resistors as shown in the typical application circuit. The device exhibit a wide operating current range of 0.2 to 00 ma with a typical dynamic impedance of Active output circuitry provides a very sharp turn-on characteristic, making the L432 excellent replacements for low-voltage zener diodes in many applications, including on-board regulation and adjustable power supplies. When used with an opto-coupler, the L432 is ideal voltage reference in isolated feedback circuits for 3.3V switching-mode power supplies. The L432 shunt regulator is available in two voltage tolerances (0.5% &.0%) and three package options (TO-92, SOT-23-3 and SO-8). FEATURES Internal amplifier with 00 ma capability Prograable output voltage to 8V 0.25 typical output impedance Pin to pin compatible with TLV43A, TS43, SC43L & AS432 Tried bandgap design 0.5% &.0% with three package options Low output noise APPLICATIONS Linear regulator controller Precision voltage reference Switching power supplies Battery operating equipment Instrumentation PCs, Computer disk drives SYMBOL & BLOCK DIAGRAM Cathode (K) Reference (R) + Cathod (K) Reference (R) -.24 Vref Anode (A) SYMBOL Anode (A) FUNCTIONAL BLOCK DIAGRAM

2 ABSOLUTE MAXIMUM RATINGS PARAMETER VALUE Cathode-Anode Reverse Breakdown Voltage - V KA 20V Anode-Cathode Forward Current - I AK A Operating Cathode Current - I KA 00 ma Reference Input Current - I REF ma Storage Temperature Range - T STG -65 to +50 C Junction Temperature - T J 50 C Lead Temperature (Soldering, 0 Seconds) - T L 300 C Continuous Power at 25 C - P D TO-92 SOIC-8 SOT mw 650 mw 200 mw RECOMMENDED CONDITIONS TYPICAL THERMAL RESISTANCES Parameter Rating Package θ JA θ JC Typ. De-rating Cathode Voltage (V KA ) V REF to 8V TO C/W 80 C/W 6.3 mw/ C Cathode Current (I K ) 0 ma SOIC-8 75 C/W 45 C/W 5.7 mw/ C SOT C/W 50 C/W.7 mw/ C ELECTRICAL SPECIFICATIONS (Ambient temperature must be derated base on power dissipation and package thermal characteristics. The conditions are: V KA = V REF and I K = 0 ma unless otherwise stated) PARAMETER TEST CONDITIONS MIN TYP MAX UNITS TEST CIRCUIT Output Voltage - V T A = 25 C, L432 (0.5%) REF T A = 25 C, L432 (%) V Line Regulation - V REF V KA = V REF to 5V mv 2 Load Regulation - V REF I K = to 00 ma mv Temperature Deviation - V REF 0 < T J < 05 C 5 2 mv Reference Input Current - I REF µa Reference Input Current Temperature Coefficient - I REF 0 < T J < 05 C µa Minimum Cathode Current for Regulation - I K(MIN) 0.2 ma Off State Leakage - I K(MIN) V REF = 0V, V KA = 5V na 3 Dynamic impedance VKA = Vref, f khz IK = 0. ma to 00 ma

3 TEST CIRCUITS V IN VKA V IN V KA VIN VKA IREF IK R IREF IK IK (OFF) VREF R2 - TEST CIRCUIT - (VKA = VREF) - TEST CIRCUIT 2 - (VKA > VREF) - TEST CIRCUIT 3 - (OFF STATE CURRENT) Applications Information Stability Selection of load capacitance when using L432 as a shunt regulator When the L432 is used as a shunt regulator, two options for selection of CL are recoended for optimal stability:. No load capacitance across the device, decouple at the load. 2. Large capacitance across the device, optional decoupling at the load. The reason for this is that L432 exhibits instability with capacitances in the range of nf to uf (approx.) at light cathode currents (up to 3mA typical). The device is less stable the lower the cathode voltage has been set for. Therefore while the device will be perfectly stable operating at a cathode current of 0mA with a 0.uF capacitor across it, it will oscillate transiently during start-up as the cathode current passes through the instability region. Selecting a very low (or preferably, no)capacitance, or alternatively a high capacitance (such as 0uF) will avoid this issue altogether. Since the user will probably wish to have local decoupling at the load anyway, the most cost effective method is to use no capacitance at all directly across the device. PCB trace/via resistance and inductance prevent the local load decoupling from causing the oscillation during the transient start-up phase. Note : if the L432 is located right at the load, so the load decoupling capacitor is directly across it, then this capacitor will have to be 00pF or uf. 3

4 Small-Signal Gain and Phase Shift VS. Frequency Test Circuit for Small Signal Gain and Phase OUT 0uF 5K 2 3 Iz L K Stability Boundary Condition For Shunt Regulation VS. Cathode Current and Load Capacitance Test Circuit for Stability R L432 R CL GND 2 3 Iz R2 Cathode Current VS. Cathode Voltage Cathode Current VS. Cathode Voltage 4

5 Reference Voltage VS. Junction Temperature Reference Impedance VS. Frequency Ratio of Delta Reference Voltage to Delta Cathode Voltage VS. Junction Temperature Reference Input Current VS. Junction Temperature Vref / Vz (-mv/v) Vz = 6V to Vref 5

6 Off-State Cathode Current VS. Junction Temperature Reference Impedance VS. Junction Temperature rz ( ) PIN CONFIGURATIONS 6

7 DEVICE SELECTION GUIDE Device L432NBG L432M3BG L432VBG L432M5BG Package TO-92 SOT-23-3 SOIC-8 SOT-23-5 Marking L432NA 2M3A L432VG 2M5A Tolerance % % % % Orders for parts with Lead-Free plating can be placed using the LXXXXXG parts name. APPLICATION CIRCUIT Vin Cin P0N02LM or P3055L Niko + D S G Vout 5V or 2V + K K R R + Cout 0uF A L43 or L432 Niko R2 Vout = ( + R R2 ) Vref 7

8 TO-92 MECHANICAL DATA A H B I C J D K E L F M G N A B F G H C E I D 8

9 SOT-23 (M3) MECHANICAL DATA A H B I 0.37 C J D K E..3 L F 0 0. M G N H C 2 3 B A I D E G F 9

10 SOIC-8(D) MECHANICAL DATA A H B I C J 0.22 D K E.27 L F M G N J D E G F I H K B C A 0

11 SOT-23 (M5) MECHANICAL DATA A e.90(typ) A H A L 0.37 b C D E D C HE L e A2 b A A