LTC1798 Series Micropower Low Dropout References U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ 200mV Max Dropout at 10mA Output Current 4µA Typical Quiescent Current 0.15% Max Initial Accuracy No Output Capacitor Required Output Sources 10mA, Sinks 2mA 40ppm/°C Max Drift Voltage Options: 2.5V, 3V, 4.1V, 5V and Adjustable U APPLICATIO S ■ ■ ■ ■ The LTC®1798/LTC1798-2.5/LTC1798-3/LTC1798-4.1/ LTC1798-5 are micropower bandgap references that combine high accuracy and low drift with very low supply current and small package size. The combination of ultralow quiescent current and low dropout voltage of only 200mV (max) makes them ideal for battery-powered equipment. The output voltage is set by an external resistor divider for the adjustable LTC1798. This series of references uses curvature compensation to obtain low temperature coefficient and trimmed thin-film resistors to achieve high output accuracy. These references can source up to 10mA and sink up to 2mA, making them ideal for precision regulator applications. They are stable without an output bypass capacitor, but are also stable with capacitance up to 1µF. This feature is important in critical applications where PC board space is a premium and fast settling is demanded. Battery-Powered Systems Handheld Instruments Precision Power Supplies A/D and D/A Converters The LTC1798 series references provided power dissipation advantages over shunt references. In addition to supply current, shunt references must also idle the entire load current to operate. The LTC1798 series is available in the SO-8 package. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATIO LTC1798-2.5 Temperature Drift 4 LTC1798-2.5 2.7V TO 12.6V 2 IN OUT 6 2.5V 0.1µF GND 1798 TA01 4 REFERENCE VOLTAGE CHANGE (mV) 2.5V Battery-Powered Reference 3 2 1 0 –1 –2 –3 –4 –40 –20 0 20 40 60 TEMPERATURE (°C) 80 100 1798 TA02 1 LTC1798 Series U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltage ....................................................... 13V Input Voltages .......................................... – 0.3v to 13V Output Voltages ........................................ – 0.3V to 13V Output Short-Circuit Duration .......................... Indefinite Operating Temperature Range (Note 2) ........................................... – 40°C to 100°C Specified Temperature Range ..................... 0°C to 70°C Storage Temperature Range (Note 3) ... – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C ORDER PART NUMBER TOP VIEW *DNC 1 8 DNC* IN 2 7 DNC* **DNC/FB 3 6 OUT GND 4 5 DNC* S8 PACKAGE 8-LEAD PLASTIC SO LTC1798CS8 LTC1798CS8-2.5 LTC1798CS8-3 LTC1798CS8-4.1 LTC1798CS8-5 S8 PART MARKING TJMAX = 125°C, θJA = 190°C/W 1798 179825 17983 179841 17985 * CONNECTED INTERNALLY. DO NOT CONNECT EXTERNAL CIRCUITRY TO THESE PINS ** DNC FOR LTC1798-2.5/LTC1798-3/ LTC1798-4.1/LTC1798-5, FB FOR LTC1798 Consult factory for parts specified with wider operating temperature range. U AVAILABLE OPTIO S PACKAGE TYPE SO-8 (S8) ORDER NUMBER PART MARKING OUTPUT VOLTAGE (V) TEMPERATURE RANGE (°C) ACCURACY (%) TEMPERATURE COEFFICIENT (ppm/°C) 2.5 0 to 70 0.15 40 LTC1798CS8-2.5 179825 3 0 to 70 0.15 40 LTC1798CS8-3 17983 4.096 0 to 70 0.15 40 LTC1798CS8-4.1 179841 5 0 to 70 0.15 40 LTC1798CS8-5 17985 Adjustable 0 to 70 0.4 40 LTC1798CS8 1798 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full specified temperature range, otherwise specifications are at TA = 25°C. VIN = VOUT(NOMINAL) + 0.2V, IOUT = 0mA unless otherwise noted. FB = OUT for the LTC1798. SYMBOL PARAMETER VIN Input Voltage Range IIN Input Current CONDITIONS MIN TYP MAX UNITS 12.6 V 4.0 6.5 8.5 µA µA 2.385 2.3945 0.4 2.5037 3.0045 4.102 5.0075 0.15 V % V V V V % ● FB = OUT for LTC1798 ● VOUT 2 Output Voltage (Note 4) LTC1798, FB = OUT LTC1798 ADJ LTC1798-2.5 LTC1798-3 LTC1798-4.1 LTC1798-5 LTC1798 All Fixed Options 2.3755 – 0.4 2.4963 2.9955 4.090 4.9925 – 0.15 2.5 3 4.096 5 LTC1798 Series ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full specified temperature range, otherwise specifications are at TA = 25°C. VIN = VOUT(NOMINAL) + 0.2V, IOUT = 0mA unless otherwise noted. FB = OUT for the LTC1798. SYMBOL PARAMETER CONDITIONS MIN en Output Voltage Noise (Note 5) 0.1Hz ≤ f ≤ 10Hz TC Output Voltage Temp Coefficient (Note 6) TMIN ≤ TJ ≤ TMAX ● VOUT/VIN Line Regulation VIN = (VOUT(NOMINAL) + 0.2V) to 12.6V ● VOUT/IOUT Load Regulation (Note 7) Sourcing 0mA to 10mA ● TYP MAX UNITS 15 40 ppm/°C 30 120 ppm/V 0.1 0.3 mV/mA 1.75 4.0 6.5 mV/mA mV/mA 8 Sinking 0mA to 2mA ● ISC Short-Circuit Output Current VOUT Shorted to GND VOUT Shorted to VIN ∆VDO Dropout Voltage (Note 8) IOUT = 0, ∆VOUT ≤ 0.1% IOUT = 10mA, ∆VOUT ≤ 0.1% VHYST Output Hysteresis (Note 9) ∆T = – 40°C to 85°C ∆T = 0°C to 70°C 200 50 ppm ppm IFB FB Pin Input Current LTC1798, OUT = FB 10 nA Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: The LTC1798 is guaranteed functional over the operating temperature range of – 40°C to 100°C. Note 3: If the part is stored outside of the specified operating temperature range, the output may shift due to hysteresis. Note 4: ESD (Electostatic Discharge) sensitive device. Extensive use of ESD protection devices are used internal to the LTC1798, however, high electrostatic discharge can damage or degrade the device. Use proper ESD handling precautions. Note 5: Peak-to-peak noise is measured with a single pole highpass filter at 0.1Hz and 2-pole lowpass filter at 10Hz. 20 2 ppmP-P 40 4 mA mA 100 200 ● ● mV mV Note 6: Temperature coefficient is the change in output voltage divided by the nominal output voltage divided by the specified temperature range. Note 7: Load regulation is measured on a pulse basis from no load to the specified load current. Output changes due to die temperature change must be taken into account separately. Note 8: Dropout voltage is (VIN – VOUT) when VOUT falls to 0.1% below its nominal value at VIN = VOUT + 0.5V. Note 9: Hysteresis in output voltage is created by package stress that differs depending on whether the IC was previously at a higher or lower temperature. Output voltage is always measured at 25°C, but the IC is cycled hot or cold before successive measurements. Hysteresis is not normally a problem for operational temperature excursions where the instrument might be stored at high or low temperature. U W TYPICAL PERFOR A CE CHARACTERISTICS LTC1798-2.5* Dropout Voltage vs Output Source Current LTC1798-2.5* Input Current vs Temperature 100 8 70 OUTPUT SHORT-CIRCUIT CURRENT (mA) VIN = 2.7V TA = 25°C 90 7 80 INPUT CURRENT (µA) DROPOUT VOLTAGE (mV) LTC1798 Series Output ShortCircuit Current vs Temperature 70 60 50 40 30 6 5 4 3 2 20 1 10 0 0 1 10 0.1 OUTPUT SOURCE CURRENT (mA) 100 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 1798 G01 1798 G02 60 TA = 25°C VIN = VOUT(NOM) + 0.2V OUTPUT SHORTED TO GND 50 40 30 20 10 OUTPUT SHORTED TO VIN 5 0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 1798 G03 *Similar performance characteristics can be expected for all voltage options. 3 LTC1798 Series U W TYPICAL PERFOR A CE CHARACTERISTICS LTC1798-2.5* Output Short-Circuit Current vs Input Voltage LTC1798-2.5* Output Short-Circuit Current vs Input Voltage 42 20 5 15 10 5 0 TA = 25°C OUTPUT SHORTED TO GND 6 8 10 INPUT VOLTAGE (V) 4 12 14 2 6 8 10 INPUT VOLTAGE (V) 4 12 1258-G04 –3 0 1 10 0.1 OUTPUT CURRENT (mA) 100 LTC1798-2.5 PSRR vs Frequency 2.5005 2.5000 6 5 4 14 POWER SUPPLY REJECTION RATIO (dB) INPUT CURRENT (µA) OUTPUT VOLTAGE (V) –2 1798 G06 TA = 25°C 12 –1 60 TA = 25°C 6 8 10 INPUT VOLTAGE (V) SOURCING 0 –5 14 7 4 1 LTC1798-2.5* Input Current vs Input Voltage 2.5010 2 SINKING 2 1798 G05 LTC1798-2.5* Output Voltage vs Input Voltage 2.4995 3 –4 41 2 TA = 25°C VIN = VOUT(NOM) + 0.2V 4 ∆VOUT FROM NO LOAD (mV) TA = 25°C OUTPUT SHORTED TO VIN OUTPUT SHORT-CIRCUIT CURRENT (mA) OUTPUT SHORT-CIRCUIT CURRENT (mA) 25 LTC1798 Series Load Regulation 2 6 8 10 INPUT VOLTAGE (V) 4 12 1798 G07 40 30 20 10 0 14 10 1k 100 FREQUENCY (Hz) 10k 1798 G09 1798 G08 LTC1798-5 Input Current vs Input Voltage in Dropout LTC1798-2.5 0.1Hz to 10Hz Noise LTC1798-2.5 Input Current vs Input Voltage in Dropout 1400 250 VIN = 2.7V TA = –55°C 1200 200 1000 INPUT CURRENT (µA) INPUT CURRENT (µA) TA = 25°C 5µV/DIV VIN = 2.7V 50 TA = 125°C 800 600 400 TA = 125°C TA = 25°C 150 100 TA = –55°C 50 200 0 0 1SEC/DIV 1798 G10 0 1 2 3 4 5 6 7 INPUT VOLTAGE (V) 8 9 10 1798 G11 4 0 0.5 1 1.5 2 2.5 3 3.5 INPUT VOLTAGE (V) 4 4.5 5 1798 G12 LTC1798 Series U U U PI FU CTIO S DNC (Pins 1, 5, 7, 8): Do Not Connect. Connected internally for post package trim. These pins must be left unconnected. R1 + R2 VOUT = 2.385V ; R1 is connected from OUT R2 to FB and R2 from FB to GND. Selecting R2 ≥ 10k will make IOUT < 250µA. IN (Pin 2): Positive Supply. Bypassing with a 0.1µF capacitor is recommended if the output loading changes. (VOUT + 0.2V) ≤ VIN ≤ 12.6V. GND (Pin 4): Negative Supply or Ground Connection. DNC (Pin 3): (LTC1798-2.5/LTC1798-3/LTC1798-4.1/ LTC1798-5) Do Not Connect. Connected internally for post package trim. This pin must be left unconnected. OUT (Pin 6): Reference Output. The output can source up to 10mA and sink up to 2mA. It is stable with output bypass capacitor ranging from 0µF to 1µF. FB (Pin 3): (LTC1798) Resistor Divider Feedback Pin. Connect a resistor divider from OUT to GND and the center tap to FB. This pin sets the output potential. W BLOCK DIAGRA 2 IN + OUT 6 – 2.385V R1 FB 3 (LTC1798) R2 GND 4 1798 BD NOTE: R1 AND R2 ARE NOT CONNECTED FOR LTC1798 5 LTC1798 Series U W U U APPLICATIO S I FOR ATIO Series references have an advantage over shunt style references. To operate, shunt references require a resistor between the power supply and the output. This resistor must be chosen to supply the maximum current that is demanded by the circuit being regulated. When the circuit being controlled is not operating at this maximum current, the shunt reference must always sink this current, resulting in high power dissipation and short battery life. The LTC1798 series low dropout references do not require a current setting resistor and can operate with any supply voltage from (VOUT(NOMINAL) + 0.2V) to 12.6V. When the circuitry being regulated does not demand current, the LTC1798 series reduces its dissipation and battery life is extended. If the reference is not delivering load current it dissipates only 10.8µW when operating on a 2.7V supply for LTC1798-2.5, yet the same connection can deliver 10mA of load current when demanded. Output Bypass Capacitor The LTC1798 series is designed to be stable with or without capacitive loads. With no capacitive load, the reference is ideal for fast settling applications, or where PC board space is at a premium. In applications with significant output loading changes, an output bypass capacitor of up to 1µF can be used to improve the output transient response. Figure 1 shows the response of the reference to a 1mA to 0µA load step with a 1µF output capacitor. If more than 1µF of output capacitance is required, a resistor in series with the capacitor is recommended to reduce the output ringing. Figure 2 illustrates the use of a damping resistor for capacitive loads greater than 1µF. Figure 3 shows the resistor and capacitor values required to achieve critical damping. LTC1798-5 5.2V TO 12.6V 2 IN OUT 5V COUT >1µF DAMPING RESISTOR <1k 1798 F02 Figure 2. Adding a Damping Resistor with Output Capacitors Greater Than 1µF 10k 1k 100 10 1 10 100 OUTPUT CAPACITOR VALUE (µF) 1000 1798 F03 Figure 3. Damping Resistance vs Output Capacitor Value 1mA 1mA IOUT IOUT 0mA 0mA VOUT 100mV/DIV VOUT 100mV/DIV 10ms/DIV 0.5ms/DIV 1798 F01a Figure 1. Reference Output Load Transient Response, 1µF Output Capacitor 6 6 GND 4 0.1µF RESISTOR VALUE (Ω) Longer Battery Life 1798 F01b LTC1798 Series U U W U APPLICATIO S I FOR ATIO Internal P-Channel Pass Transistor The LTC1798 series features an internal P-channel MOSFET pass transistor. This provides several advantages over similar designs using a PNP bipolar pass transistor. U PACKAGE DESCRIPTIO These references consume only 4µA of quiescent current under light and heavy loads as well as in dropout; whereas, PNP-based references waste considerable amounts of current when the pass transistor is saturated. In addition, the LTC1798 series provides a lower dropout voltage (200mV max) than PNP-based references. Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 (0.406 – 1.270) 0.014 – 0.019 (0.355 – 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 2 3 4 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) BSC Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. SO8 1298 7 LTC1798 Series U TYPICAL APPLICATIO S Micropower Low Dropout Negative Reference Supply Splitter 0.2V ≤ VCC ≤ 8.5V 2 IN 6 OUT LTC1798-2.5 2 VCC = 5V LTC1798-3 IN OUT 6 0.1µF 2 – 1/2 LTC1542 3 + 0.1µF 8 1 GND GND 4 4 VOUT = – 3V 4 2.5V VIRTUAL 0.1µF GROUND 1798 TA04 1798 TA03 VSS = – 4V Low Power, Low Voltage Supply Reference for LTC1096L ANALOG INPUT 0V TO 3V RANGE 1 CS/ VCC 2 SHDN +IN CLK LTC1096L 3 –IN DOUT 4 GND VREF 1µF 8 MPU 7 6 5 SERIAL DATA LINK SERIAL DATA LINK (MICROWIRETM AND SPI COMPATIBLE) 6 OUT 4 GND IN LTC1798-3 2 VIN 3.2V TO 0.1µF 12.6V 1798 TA05 MICROWIRE is a trademark of National Semiconductor Corporation. RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT®1389 Nanopower Precision Shunt Voltage Reference 800nA Quiescent Current, 0.05% Max, 10ppm/°C Max Drift 1.25V and 2.5V Versions, SO-8 Package LT1634 Micropower Precision Shunt Voltage Reference 0.05% Max, 25ppm/°C Max Drift, 1.25V, 2.5V, 4.096V and 5V Outputs LT1460 Micropower Series Reference 0.075% Max, 10ppm/°C Max Drift, 2.5V, 5V and 10V Outputs LT1461 Micropower Precision Series Voltage Reference 0.04% Max, 3ppm/°C Max Drift, 35µA Quiescent Current LT1790 SOT-23, LDO Precision Micropower Reference 0.05% Max, 10ppm/°C Max, 2.5V, 60µA Supply 8 Linear Technology Corporation 1798fa LT/LCG 1100 2K REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1999