LX8942

LX8942 TM ® Low Dropout Dual Regulator P RODUCTION D ATA S HEET DESCRIPTION The Microsemi LX8942 is a dual 8.2V/5V positive voltage regulator. One output is a high current (up to 1000mA) regulator that can be turned on or off by a high impedance low current TTL compatible switch. The second or standby output remains on regardless. The on/off switch not only shuts off the high current output but actually puts the IC in a micropower mode, achieving low quiescent current. This unique characteristic coupled with an extremely low dropout, (0.55V for output current of 10mA) makes the LX8942 well suited for power systems that require standby memory. The LX8942 includes other features which were originally designed for automotive applications. These include protection from reverse battery installations, double battery jumps and load dump (transients). The high current regulator has over voltage shutdown to protect both the internal circuitry and the load during line transients, such as load dump (60V). In addition, the high current regulator design also has builtin protection for short circuit and thermal overload. During these fault conditions of the primary output, the standby regulator will continue to power its load. The LX8942 is the 8.2 volt, ±5% version of a family of dual regulators with a standby output voltage of 5V. Other high-current outputs programmed for 5V and 12V regulation are available in the SG29055, SG29125 devices. They are designed to function over the full automotive ambient temperature range of -40°C to 85°C. KEY FEATURES 2% Internally Trimmed Output Two regulated outputs Output current in excess of 1000mA Low quiescent current standby regulator Drop-out Voltage, Input-output differential -0.6V, 16Ω Load) Reverse Polarity Transient Input Voltage (VIN) (1% Duty Cycle, T < 100ms, VOUT1 > -9V, 16Ω Load) Output Capacitor (VOUT1 to GND & VSB to GND) Output Capacitor ESR Value Symbol VIN VIL VIH LX8942 Typ Units V V V mA V µF V V µF Ω Min 9 2 5 0.1 Max 26 0.8 1000 60 -15 -50 P D PACKAGE DATA 10 0.5 5.0 Copyright © 2005 Rev. 1.2, 2006-01-20 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 2 LX8942 TM ® Low Dropout Dual Regulator P RODUCTION D ATA S HEET Unless otherwise specified, the following specifications apply over the operating ambient temperature 0°C ≤ TA ≤ 70°C except where otherwise noted and the following test conditions: TA = 25°C, VIN = 14V, IO1 = 50mA for VOUT1 and 10mA for VSB and are for DC characteristics only. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the ambient temperature. Parameter VOLTAGE OUTPUT (VOUT1) SECTION ELECTRICAL CHARACTERISTICS W WW . Microsemi . C OM Symbol VOUT1 Test Conditions 9V < VIN < 26V, IO1 < 1000mA 9V < VIN < 16V, IO1 = 5mA 9V < VIN < 26V, IO1 = 5mA 5mA < IO1 < 1000mA 500mADC and 10mARMS, 100Hz – 10kHz IO1 < 10mA, No Load on Standby IO1 = 500mA, No Load on Standby IO1 = 750mA, No Load on Standby 10Hz – 100kHz FO1 = 120Hz IO1 = 500mA IO1 = 1000mA Min 7.6 LX8942 Typ 8.0 4 10 10 200 2 40 90 100 20 66 0.45 0.7 1.8 31 70 Max 8.4 25 50 50 100 Units V mV mV mV mΩ mA mA mA µVRMS mV / 1000hr dB V V A V V µA µA V mV mV mV Ω mA µVRMS mV / 1000hr dB V mA V Output Voltage (NOTE 1) Line Regulation Load Regulation Output Impedance Quiescent Current Output Noise Voltage Long Term Stability Ripple Rejection Dropout Voltage Current Limit Maximum Operational Input Voltage Maximum Line Transient ON / OFF Switch ON / OFF Switch STANDBY OUTPUT (VSB) SECTION 0.60 1.2 1.0 VIN VIN IIH IIL VSB Double Battery VO1 < 9V IO1 = 10mA, Pin 4 = 2.4V IO1 = 10mA, Pin 4 = 0.4V 6V < VIN < 26V, ISB < 60mA 6V < VIN < 26V 1mA < ISB < 35mA 1mA < ISB < 60mA 1mADC and 1mARMS, 100Hz – 10kHz ISB < 10mA, VOUT1 OFF 10Hz – 100kHz FSB = 120Hz ISB < 60mA VIN 4.75V < VSB < 6V 60 60 26.5 60 -10 4.75 10 5.0 4 10 25 1 1.2 300 20 66 0.55 100 70 0.70 5.25 50 25 50 3 Output Voltage (Note 1) Line Regulation Load Regulation Output Impedance Quiescent Current Output Noise Voltage Long Term Stability Ripple Rejection Dropout Voltage Current Limit Maximum Line Transient Note 1: The Temperature Extremes are Guaranteed but not 100% Production Tested. E ELECTRICALS Copyright © 2005 Rev. 1.2, 2006-01-20 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 3 LX8942 TM ® Low Dropout Dual Regulator P RODUCTION D ATA S HEET TYPICAL CIRCUIT WAVEFORMS W WW . Microsemi . C OM 60V Load Dump 33V Double Battery 26V 14V INPUT VOLTAGE PIN 1(V) 14V 4V 0V 2V ON/OFF SWITCH 0.8V 8.2V 8.2V 3.5V 8.2V 8.2V 8.2V OUTPUT VOLTAGE 2 (V) 5V 0V STANDBY VOLTAGE PIN 5 (V) System Conditions 5V 3.7V TURN ON LOAD DUMP LOW VIN LINE NOISE, ETC. VOUT SHORT CIRCUIT THERMAL SHUTDOWN TURN OFF A APPLICATION Copyright © 2005 Rev. 1.2, 2006-01-20 Microsemi Integrated Products Division 11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570 Page 4 LX8942 TM ® Low Dropout Dual Regulator P RODUCTION D ATA S HEET APPLICATION NOTE The advantages of using a low-dropout regulator such as the LX8942 are the need for less “headroom” for full regulation, and the inherent reverse polarity protection provided by the PNP output device. A typical NPN regulator design requires an input to output differential of approximately two volts minimum. This is due to the 2Vbe + Vcesat of the NPN Darlington used in the output, coupled with the voltage drop across the current limit resistor. In contrast, the “PNP Regulator” uses a single series pass transistor with its single Vcesat, thus the lower input to output voltage differential or dropout voltage. In addition to a low dropout voltage, an important advantage of the LX8942 series is low quiescent current in the standby mode. When the high current or primary regulator is shut off, the regulator enters a micropower mode. Here all but the most essential circuitry to power the standby output is deactivated. This allows the lowest possible quiescent current (typical around 1.2mA), a vital factor when used in a battery powered system. In some applications the regulator output voltage is used not only as a power supply but also as a voltage reference for control systems. In such cases not just the temperature stability of the output is important but also the initial accuracy. The LX8942 fills this need as the internal bandgap reference is trimmed allowing a typical output voltage tolerance of ±1%. EXTERNAL CAPACITORS To stabilize the outputs and prevent oscillation (perhaps by many volts) external capacitors are required. The minimum recommended value for the output capacitors is 47μF for the 8.2V output and 100µF for the 5V output. The actual size and type will likely vary according to the particular application, e.g., operating temperature range and load. Another consideration is the effective series resistance (ESR) of the capacitor. Capacitor ESR will vary by manufacturer. Consequently, some evaluation may be required to determine the minimum value of the output capacitors. Generally worst case occurs at the maximum load and minimum ambient temperature. The size of the output capacitor can be increased to any value above the minimum. One possible advantage of this would be to maintain the output voltage during brief periods of negative input transients. The output capacitors chosen should be rated for the full range of ambient temperature over which the circuit will be exposed and expected to operate. For example, many aluminum type electrolytic capacitors will freeze at -30°C. The effective capacitance is reduced to zero in such a situation. Capacitors rated for -40°C operation must be used in order to maintain regulator stability at that temperature. Tantalum capacitors satisfy this requirement. STANDBY OUTPUT The LX8942 differs from most fixed voltage regulators in that it is equipped with two regulator outputs instead of one. The additional output is intended for use in systems requiring standby memory circuits. While the high current regulator output can be controlled with the ON/OFF pin described below, the standby remains on under all conditions as long as sufficient input voltage is applied to the IC. Thus, memory and other circuits powered by this output remain unaffected by positive line transients, thermal shutdown, etc. The standby regulator circuit is designed so that the quiescent current to the IC is very low (