19-1139; Rev 3; 5/98 Low-Noise, Precision, +2.5V/+4.096V/+5V Voltage References ____________________________Features ♦ Low 1.0ppm/°C Temperature Coefficient ♦ Very Low 1.5µVp-p Noise (0.1Hz to 10Hz) ♦ ±0.02% Initial Accuracy ♦ ±15mA Output Source and Sink Current ♦ Low, 18mW Power Consumption (MAX6225) ♦ Industry-Standard Pinout ♦ Optional Noise Reduction and Voltage Trim ♦ Excellent Transient Response ♦ 8-Pin SO Package Available ♦ Low 20ppm/1000h Long-Term Stability ♦ Stable for All Capacitive Loads Ordering Information Applications High-Resolution Analog-to-Digital and Digital-to-Analog Converters High-Accuracy Reference Standard High-Accuracy Industrial and Process Control Digital Voltmeters ATE Equipment Precision Current Sources PART TEMP. RANGE PINPACKAGE MAX TEMPCO (ppm/°C) MAX6225ACPA 0°C to +70°C 8 Plastic DIP 2.0 MAX6225BCPA MAX6225ACSA MAX6225BCSA MAX6225AEPA MAX6225BEPA MAX6225AESA MAX6225BESA MAX6225AMJA MAX6225BMJA 0°C to +70°C 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C -40°C to +85°C -40°C to +85°C -55°C to +125°C -55°C to +125°C 8 Plastic DIP 8 SO 8 SO 8 Plastic DIP 8 Plastic DIP 8 SO 8 SO 8 CERDIP 8 CERDIP 5.0 2.0 5.0 3.0 7.0 3.0 7.0 5.0 8.0 Ordering Information continued at end of data sheet. Typical Operating Circuit TOP VIEW 8V TO 36V INPUT IN OUT 2.2µF * NR MAX6225 MAX6241 MAX6250 Pin Configuration REFERENCE OUT I.C. 1 IN 2 NR 3 TRIM 2.2µF * MAX6225 MAX6241 MAX6250 GND 4 8 I.C. 7 I.C. 6 OUT 5 TRIM GND DIP/SO *OPTIONAL I.C. = INTERNALLY CONNECTED; DO NOT USE ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468. MAX6225/MAX6241/MAX6250 General Description The MAX6225/MAX6241/MAX6250 are low-noise, precision voltage references with extremely low 1ppm/°C temperature coefficients and excellent ±0.02% initial accuracy. These devices feature buried-zener technology for lowest noise performance. Load-regulation specifications are guaranteed for source and sink currents up to 15mA. Excellent line and load regulation and low output impedance at high frequency make them ideal for high-resolution data-conversion systems up to 16 bits. The MAX6225 is set for 2.500V output, the MAX6241 is set for 4.096V output, and the MAX6250 is set for 5.000V output. All three provide for the option of external trimming and noise reduction. MAX6225/MAX6241/MAX6250 Low-Noise, Precision, +2.5V/+4.096V/+5V Voltage References ABSOLUTE MAXIMUM RATINGS (Voltages Referenced to GND) IN..............................................................................-0.3V to +40V OUT, TRIM ...............................................................-0.3V to +12V NR ..............................................................................-0.3V to +6V OUT Short Circuit to GND Duration (VIN ≤ 12V)..........Continuous OUT Short Circuit to GND Duration (VIN ≤ 40V) ....................5sec OUT Short Circuit to IN Duration (VIN ≤ 12V) ..............Continuous Continuous Power Dissipation (TA = +70°C) Plastic DIP (derate 9.09mW/°C above +70°C)................727mW SO (derate 5.88mW/°C above +70°C) ............................471mW CERDIP (derate 8.00mW/°C above +70°C) ....................640mW Operating Temperature Ranges MAX62_ _ _C_ A .....................................................0°C to +70°C MAX62_ _ _E_ A ..................................................-40°C to +85°C MAX62_ _ _MJA ................................................-55°C to +125°C Storage Temperature Range ..............................-65°C to +150°C Lead Temperature (soldering, 10sec)...............................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS—MAX6225 (VIN = 10V, IOUT = 0mA, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Input Voltage Range Output Voltage Output Voltage Temperature Coefficient (Note 1) SYMBOL CONDITIONS TA MIN C, E, M 8 MAX6225A +25°C 2.499 2.500 2.501 MAX6225B +25°C 2.497 2.500 2.503 VIN VOUT TCVOUT UNITS 36 V C 1.0 2.0 MAX6225AE_A E 1.5 3.0 MAX6225AMJA M 2.0 5.0 MAX6225BC_A C 2.5 5.0 MAX6225BE_A E 2.5 7.0 MAX6225BMJA M 2.5 8.0 +25°C 10 18 ∆VOUT / ∆VIN C 30 E 35 M +25°C 10V ≤ VIN ≤ 36V 2 MAX MAX6225AC_A 8V ≤ VIN ≤ 10V Line Regulation (Note 2) TYP 45 2 C 5 7 E 8 M 10 _______________________________________________________________________________________ V ppm/°C ppm/V Low-Noise, Precision, +2.5V/+4.096V/+5V Voltage References (VIN = 10V, IOUT = 0mA, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS Sourcing: 0mA ≤ IOUT ≤ 15mA Load Regulation (Note 2) Supply Current ∆VOUT/ ∆IOUT IIN Trim-Adjustment Range Turn-On Settling Time Output Noise Voltage (Note 3) ∆VOUT tON en Temperature Hysteresis Long-Term Stability Sinking: -15mA ≤ IOUT ≤ 0mA Sinking: -15mA ≤ IOUT ≤ 0mA ∆VOUT / t TA TYP MAX C MIN 1 6 E 1 7 M 3 15 C 1 6 E 1 7 M 10 30 +25°C 1.8 C, E, M 2.7 3.0 ±15 ±25 UNITS ppm/mA mA Figure 1 C, E, M To ±0.01% of final value +25°C 5 mV µs 0.1Hz ≤ f ≤ 10Hz +25°C 1.5 µVp-p 10Hz ≤ f ≤ 1kHz +25°C 1.3 (Note 4) +25°C 20 ppm +25°C 20 ppm/ 1000h 2.8 µVRMS _______________________________________________________________________________________ 3 MAX6225/MAX6241/MAX6250 ELECTRICAL CHARACTERISTICS—MAX6225 (continued) MAX6225/MAX6241/MAX6250 Low-Noise, Precision, +2.5V/+4.096V/+5V Voltage References ELECTRICAL CHARACTERISTICS—MAX6241 (VIN = 10V, IOUT = 0mA, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Input Voltage Range Output Voltage Output Voltage Temperature Coefficient (Note 1) SYMBOL CONDITIONS TA MIN C, E, M 8 MAX6241A +25°C 4.095 4.096 4.097 MAX6241B +25°C 4.092 4.096 4.100 VIN VOUT TCVOUT 1.0 2.0 E 1.5 3.0 MAX6241AMJA M 2.0 5.0 MAX6241BC_A C 2.5 5.0 MAX6241BE_A E 2.5 7.0 M 2.5 8.0 +25°C 10 18 ∆VOUT / ∆VIN ∆VOUT / ∆IOUT Sinking: -15mA ≤ IOUT ≤ 0mA Turn-On Settling Time Output Noise Voltage (Note 3) IIN ∆VOUT tON en Temperature Hysteresis Long-Term Stability 4 ∆VOUT / t C 30 E 35 M 45 +25°C Sourcing: 0mA ≤ IOUT ≤ 15mA Trim-Adjustment Range V C 10V ≤ VIN ≤ 36V Supply Current UNITS 36 MAX6241AE_A 8V ≤ VIN ≤ 10V Load Regulation (Note 2) MAX MAX6241AC_A MAX6241BMJA Line Regulation (Note 2) TYP 2 C 5 V ppm/°C ppm/V 7 E 8 M 10 C 1 6 E 1 7 M 3 9 C 1 6 E 1 7 M 7 18 +25°C 1.9 2.9 C, E, M 3.2 ±40 mA Figure 1 C, E, M To ±0.01% of final value +25°C 8 µs 0.1Hz ≤ f ≤ 10Hz +25°C 2.4 µVp-p 10Hz ≤ f ≤ 1kHz +25°C 2.0 (Note 4) +25°C 20 ppm 20 ppm/ 1000h +25°C ±24 ppm/mA ppm/mA _______________________________________________________________________________________ mV 4.0 µVRMS Low-Noise, Precision, +2.5V/+4.096V/+5V Voltage References (VIN = 10V, IOUT = 0mA, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER Input Voltage Range Output Voltage SYMBOL VIN VOUT Output Voltage Temperature Coefficient (Note 1) CONDITIONS TCVOUT 5.001 MAX6250B +25°C 4.995 5.000 5.005 MAX6250AC_A C 1.0 2.0 MAX6250AE_A E 1.5 3.0 MAX6250AMJA M 2.0 5.0 MAX6250BC_A C 2.5 5.0 MAX6250BE_A E 2.5 7.0 MAX6250BMJA M 2.5 8.0 +25°C 10 18 Output Noise Voltage (Note 3) en Temperature Hysteresis Long-Term Stability Note 1: Note 2: Note 3: Note 4: ∆VOUT / t C 30 E 35 M 45 +25°C IIN ton V 5.000 ∆VOUT / ∆IOUT ∆VOUT 36 8 ∆VOUT / ∆VIN Turn-On Settling Time UNITS 4.999 Sinking: -15mA ≤ IOUT ≤ 0mA Trim-Adjustment Range MAX +25°C Sourcing: 0mA ≤ IOUT ≤ 15mA Supply Current TYP C, E, M 10V ≤ VIN ≤ 36V Load Regulation (Note 2) MIN MAX6250A 8V ≤ VIN ≤ 10V Line Regulation (Note 2) TA 2 C 5 V ppm/°C ppm/V 7 E 8 M 10 C 1 6 E 1 7 M 2 9 C 1 6 E 1 7 M 6 15 +25°C 2.0 3.0 C, E, M 3.3 ±30 ppm/mA mA Figure 1 C, E, M ±50 mV To ±0.01% of final value +25°C 10 µs 0.1Hz ≤ f ≤ 10Hz +25°C 3.0 10Hz ≤ f ≤ 1kHz +25°C 2.5 (Note 4) +25°C 20 ppm +25°C 20 ppm/ 1000h µVp-p 5.0 µVRMS Temperature coefficient is measured by the box method; i.e., the maximum ∆VOUT is divided by ∆T x VOUT. Line regulation (∆VOUT / (VOUT x ∆VIN)) and load regulation (∆VOUT / (VOUT x ∆IOUT)) are measured with pulses and do not include output voltage changes due to die-temperature changes. Noise specifications are 100% tested for the 10Hz to 1kHz bandwidth. Contact factory for 100% noise testing in the 0.1Hz to 10Hz bandwidth. Temperature hysteresis is specified at TA = +25°C by measuring VOUT before and after changing temperature by +25°C using the PDIP package. _______________________________________________________________________________________ 5 MAX6225/MAX6241/MAX6250 ELECTRICAL CHARACTERISTICS—MAX6250 __________________________________________Typical Operating Characteristics (VIN = 10V, IOUT = 0mA, TA = +25°C, unless otherwise noted.) MAX6241 NORMALIZED OUTPUT VOLTAGE vs. TEMPERATURE 200 0.5 100 0 0 -0.5 -100 -1.0 -200 0.5 125 0 0 -0.5 -1.5 -55 -35 -15 5 25 65 45 5 25 45 -250 85 105 125 65 120 0.2 80 0.1 40 0 -0.1 -40 -0.2 -80 -0.3 -120 25 45 65 -160 85 105 125 MAX6250 CHANGE IN OUTPUT VOLTAGE vs. OUTPUT CURRENT MAX6241 CHANGE IN OUTPUT VOLTAGE vs. OUTPUT CURRENT MAX6225 CHANGE IN OUTPUT VOLTAGE vs. OUTPUT CURRENT TA = +85°C 150 100 TA = +85°C -100 ∆VOUT (µV) 50 100 TA = -40°C TA = +25°C 0 TA = -40°C TA = +25°C 0 10 20 30 40 -250 -40 -30 -20 -10 IOUT (mA) 0 10 20 30 -40 -30 -20 40 CHANGE IN OUTPUT VOLTAGE vs. INPUT VOLTAGE 2.8 SUPPLY CURRENT (mA) 30 20 10 0 MAX6250 2.4 MAX6241 MAX6225 2.2 2.0 1.8 1.6 3.5 2.5 MAX6250 2.0 MAX6225 1.0 1.0 10 15 20 VIN (V) 25 30 35 40 40 MAX6241 1.2 -20 30 1.5 1.4 -10 20 3.0 2.6 40 10 SUPPLY CURRENT vs. TEMPERATURE SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX6225-08 50 0 IOUT (mA) 3.0 MAX6225-04 60 5 -10 IOUT (mA) SUPPLY CURRENT (mA) -10 TA = +85°C -200 -300 -40 -30 -20 TA = +25°C -50 -150 -200 -400 TA = -40°C MAX6225-09 -300 0 -100 -100 -200 MAX6225-05 200 MAX6225-06 MAX6225-07 300 200 0 5 TEMPERATURE (°C) ∆VOUT (µV) ∆VOUT (µV) 160 0.3 -0.4 -55 -35 -15 100 6 200 0.4 TEMPERATURE (°C) 200 0 240 0.5 TEMPERATURE (°C) 300 280 0.6 0 -125 -1 -55 -35 -15 -300 85 105 125 ∆VOUT (mV) 1.0 250 1.0 MAX6225 03 0.7 375 ∆VOUT (ppm) 300 ∆VOUT (mV) ∆VOUT (mV) 1.5 MAX6225 -02 1.5 400 ∆VOUT (ppm) MAX6225 -01 2.0 MAX6225 NORMALIZED OUTPUT VOLTAGE vs. TEMPERATURE 0 5 10 15 20 25 SUPPLY VOLTAGE (V) 30 35 40 -55 -35 -15 5 25 45 65 TEMPERATURE (°C) _______________________________________________________________________________________ 85 105 125 ∆VOUT (ppm) MAX6250 NORMALIZED OUTPUT VOLTAGE vs. TEMPERATURE ∆VOUT (ppm) MAX6225/MAX6241/MAX6250 Low-Noise, Precision, +2.5V/+4.096V/+5V Voltage References Low-Noise, Precision, +2.5V/+4.096V/+5V Voltage References MAX6241 OUTPUT NOISE-VOLTAGE DENSITY vs. FREQUENCY 30 25 20 CNR = 1µF 15 10 70 50 40 30 10 0 0 100 1k CNR = 1µF 20 5 10 CNR = 0µF 60 1k CNR = 1µF 20 10 100 MAX6225-18 VOUT, 1µV/div VOUT, 1µV/div VOUT, 0.5µV/div COUT = CNR = 0µF 1sec/div RIPPLE REJECTION vs. FREQUENCY (CNR = 0µF) RIPPLE REJECTION vs. FREQUENCY (CNR = 1µF) OUTPUT IMPEDANCE vs. FREQUENCY MAX6225 ISINK = 5mA 100 MAX6241 90 MAX6250 80 70 ISOURCE = 5mA 100k 85 MAX6250 80 75 70 65 60 60 1M MAX6225 MAX6241 90 RIPPLE REJECTION (dB) RIPPLE REJECTION (dB) 1 95 MAX6225-14 MAX6225-13 120 110 10 10k MAX6250 0.1Hz to 10Hz NOISE 1sec/div 100 1k MAX6225-16 1sec/div OUTPUT IMPEDANCE (Ω) 30 10k COUT = CNR = 0µF 1k 10k FREQUENCY (Hz) 40 FREQUENCY (Hz) MAX6225-17 100 50 MAX6241 0.1Hz to 10Hz NOISE COUT = CNR = 0µF 10 60 FREQUENCY (Hz) MAX6225 0.1Hz to 10Hz NOISE 0.01 CNR = 0µF 70 0 100 FREQUENCY (Hz) 0.1 80 10 10 10k 90 MAX6225-15 CNR = 0µF 35 100 OUTPUT NOISE DENSITY (nV/√ Hz) 40 80 OUTPUT NOISE DENSITY (nV/√ Hz) 45 MAX6225-11 90 MAX6225-10 OUTPUT NOISE DENSITY (nV/√ Hz) 50 MAX6250 OUTPUT NOISE-VOLTAGE DENSITY vs. FREQUENCY MAX6225-12 MAX6225 OUTPUT NOISE-VOLTAGE DENSITY vs. FREQUENCY 10 100 1k FREQUENCY (Hz) 10k 10 100 1k 10k FREQUENCY (Hz) _______________________________________________________________________________________ 7 MAX6225/MAX6241/MAX6250 ____________________________Typical Operating Characteristics (continued) (VIN = 10V, IOUT = 0mA, TA = +25°C, unless otherwise noted.) MAX6225/MAX6241/MAX6250 Low-Noise, Precision, +2.5V/+4.096V/+5V Voltage References ____________________________Typical Operating Characteristics (continued) (VIN = 10V, IOUT = 0mA, TA = +25°C, unless otherwise noted.) LOAD-TRANSIENT RESPONSE (SOURCING) LOAD-TRANSIENT RESPONSE (SINKING) MAX6225-19 MAX6225-20 0mA A 10mA A -10mA 0mA B B 2µs/div 2µs/div A: IOUT, 10mA/div (SINKING) B: VOUT, 500µV/div A: IOUT, 10mA/div (SOURCING) B: VOUT, 500µV/div MAX6225 TURN-ON AND TURN-OFF TRANSIENT RESPONSE LOAD-TRANSIENT RESPONSE MAX6225-21 MAX6225-26 -10mA A +10V A +10mA 0V B B VIN = 10V COUT = CNR = 0µF CIN = COUT = CNR = 0µF 1µs/div 1µs/div A: IOUT (±10mA SOURCE AND SINK), 20mA/div, AC COUPLED B: VOUT, 20mV/div, AC COUPLED A: B: VIN, 10V/div VOUT, 1V/div MAX6250 TURN-ON AND TURN-OFF TRANSIENT RESPONSE MAX6241 TURN-ON AND TURN-OFF TRANSIENT RESPONSE MAX6225-27 MAX6225-25 +10V A +10V A 0V 0V B B CIN = COUT = CNR = 0µF CIN = COUT = CNR = 0µF 1µs/div 1µs/div A: VIN, 10V/div B: VOUT, 1V/div 8 A: VIN, 10V/div B: VOUT, 1V/div _______________________________________________________________________________________ Low-Noise, Precision, +2.5V/+4.096V/+5V Voltage References PIN NAME 1, 7, 8 I.C. Internally Connected. Do not use. 2 IN Positive Power-Supply Input NR Noise Reduction. Optional capacitor connection for wideband noise reduction. Leave open if not used (Figure 2). 3 FUNCTION 4 GND Ground 5 TRIM External Trim Input. Allows ±1% output adjustment (Figure 1). Leave open if not used. 6 OUT Voltage Reference Output Noise Reduction To augment wideband noise reduction, add a 1µF capacitor to the NR pin (Figure 2). Larger values do not improve noise appreciably ( see Typical Operating Characteristics). Noise in the power-supply input can affect output noise, but can be reduced by adding an optional bypass capacitor to the IN pin and GND. Bypassing The MAX6225/MAX6241/MAX6250 are stable with capacitive load values from 0µF to 100µF, for all values of load current. Adding an output bypass capacitor can help reduce noise and output glitching caused by load transients. Applications Information Negative Regulator Detailed Description Temperature Stability The MAX6225/MAX6241/MAX6250 are highly stable, low-noise voltage references that use a low-power temperature-compensation scheme to achieve laboratorystandard temperature stability. This produces a nearly flat temperature curve, yet does not require the power associated with heated references. The output voltage can be trimmed a minimum of 0.6% by connecting a 10kΩ potentiometer between OUT and GND, and connecting its tap to the TRIM pin, as shown in Figure 1. The external trimming does not affect temperature stability. Figure 3 shows how both a +5V and -5V precision reference can be obtained from a single unregulated +5V supply. A MAX681 generates approximately ±9V to operate the MAX6250 reference and MAX432 inverting amplifier. The +5V is inverted by the MAX432 chopperstabilized amplifier. Resistor R1 is optional, and may be used to trim the ±5V references. R2 and R4 should be matched, both in absolute resistance and temperature coefficient. R3 is optional, and is adjusted to set the -5V reference. 8V TO 36V INPUT 8V TO 36V INPUT IN IN REFERENCE OUT OUT NR MAX6225 MAX6241 MAX6250 * TRIM GND REFERENCE OUT OUT 10k NR 1µF MAX6225 MAX6241 MAX6250 TRIM GND *OPTIONAL Figure 1. Output Voltage Adjustment Figure 2. Noise-Reduction Capacitor _______________________________________________________________________________________ 9 MAX6225/MAX6241/MAX6250 _____________________Pin Description MAX6225/MAX6241/MAX6250 Low-Noise, Precision, +2.5V/+4.096V/+5V Voltage References +5V INPUT 3.3µF C1+ VCC V+ +REFERENCE OUT IN C1- OUT R2 100k MAX865 3.3µF C1 2.2µF C2+ C2- GND MAX6250 V- NR TRIM GND R1 10k C3 2.2µF C2 1µF 2.2µF R3 1k C4 1µF MAX432 R4 100k -REFERENCE OUT Figure 3. +5V and -5V References from a Single +5V Supply Ordering Information (continued) PART TEMP. RANGE PINPACKAGE MAX TEMPCO (ppm/°C) MAX6241ACPA 0°C to +70°C 8 Plastic DIP 2.0 MAX6241BCPA MAX6241ACSA MAX6241BCSA MAX6241AEPA MAX6241BEPA MAX6241AESA MAX6241BESA MAX6241AMJA MAX6241BMJA MAX6250ACPA MAX6250BCPA MAX6250ACSA MAX6250BCSA MAX6250AEPA MAX6250BEPA MAX6250AESA MAX6250BESA MAX6250AMJA MAX6250BMJA 0°C to +70°C 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C -40°C to +85°C -40°C to +85°C -55°C to +125°C -55°C to +125°C 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C -40°C to +85°C -40°C to +85°C -55°C to +125°C -55°C to +125°C 8 Plastic DIP 8 SO 8 SO 8 Plastic DIP 8 Plastic DIP 8 SO 8 SO 8 CERDIP 8 CERDIP 8 Plastic DIP 8 Plastic DIP 8 SO 8 SO 8 Plastic DIP 8 Plastic DIP 8 SO 8 SO 8 CERDIP 8 CERDIP 5.0 2.0 5.0 3.0 7.0 3.0 7.0 5.0 8.0 2.0 5.0 2.0 5.0 3.0 7.0 3.0 7.0 5.0 8.0 10 ___________________Chip Information TRANSISTOR COUNT: 435 ______________________________________________________________________________________ Low-Noise, Precision, +2.5V/+4.096V/+5V Voltage References SOICN.EPS PDIPN.EPS ______________________________________________________________________________________ 11 MAX6225/MAX6241/MAX6250 ________________________________________________________Package Information ___________________________________________Package Information (continued) CDIPS.EPS MAX6225/MAX6241/MAX6250 Low-Noise, Precision, +2.5V/+4.096V/+5V Voltage References Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.