CN951

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Document overview

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Technical content

Features

 Op Amp + Comparator + Reference  Operating Current: 15uA  Rail-to-Rail Inputs and Outputs  2.5V to 5.5V Supply Voltage Range  Unity-Gain Stable  Internal 1.211V ±2% Bandgap Reference  Internal Comparator Hysteresis: ±7mV(14mV)  Op Amp Capable of Driving up to 1nF Load  Operating Temperature Range: －40℃ to 85 ℃  Available in SOP8 Package  Lead-free, Rohs-compliant and Halogen-free Pin Assignment

w w w . c o n s o n a n c e - e l e c . c o m 3 R e v 1 . 0 Pin Description Pin No. Symbol Description 1 AMPOUT Op Amp Output. 2 AMPIN- Inverting Op Amp Input. 3 AMPIN+ Non-inverting Op Amp Input. 4 GND Negative Terminal of Power Supply or Ground. 5 COMPIN+ Non-inverting Comparator Input.

6 REF

Reference Voltage Output. The reference voltage is 1.211V typical with ±2% accuracy . This pin is also connected to the inverting input of comparator. 7 COMPOUT Comparator Output. 8 VCC Positive Terminal of Power Supply. ABSOLUTE MAXIMUM RATINGS Terminal Voltage (With Respect to GND) Input/Output Current Short-Circuit Duration REF and AMPOUT……….Continuous Thermal Resistance…………………....200°C/W 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.

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Electrical Characteristics

(VCC=3V , TA= －40℃ to 85 ℃, Typical values are at TA=25℃, unless otherwise noted.) Parameters Symbol Test Conditions Mi n T y p M a x U n i t Operating V oltage Range V C C 2 . 5 5 . 5 V Operating Current I VCC V C C = 3 . 0 V 8 1 4 2 0 uA V C C = 5 . 0 V 9 1 5 2 1 Reference Reference V oltage V REF 1.187 1.211 1.235 V Load Regulation IOUT＝±20μA, TA= +25°C 0.1 % Comparator Input Offset V oltage V OS 1 4 m V Upper Trip Point Vup COMPIN+ rises VREF＋0.007 V Lower Trip Point Vlow COMPIN+ falls VREF－0.007 V Input Leakage Current －1 0 0 . 0 1 1 0 nA Common-Mode Input Range CMVR GND VCC V Common-Mode Rejection Ratio CMRR GND to VCC 0.1 1 mV/V Power-Supply Rejection Ratio PSRR VCC = 2.5V to 5.5V 0.05 1 mV/V Propagation Delay tpd CL = 100pF, VCC = 5V , 5mV Overdrive 2 5 μs CL=100pF, VCC=5V , 20mV Overdrive 6 Output High V oltage V OH I SOURCE = 8mA VCC－0.4V V Output Low V oltage V OL I SINK = 10mA 0.4V V OP AMP I n p u t O f f s e t V o l t a g e V o s 4 m V Input Bias Current I B 0.01 10 nA Large-Signal Gain (No Load) Avol AMPOUT = 0.5V to 5V , VCC －GND = 5V 100 1000 V/mV Large-Signal Gain (100kΩ Load to GND) Avol AMPOUT = 0.5V to 4.5V , VCC－GND = 5V 4 0 1 5 0 V / m V Gain Bandwidth GBW A V = 1V/V , VCC－GND = 5V 4 0 k H z Slew Rate SR A V = 1V/V , VCC－GND = 5V 2 0 V / m s Common-Mode Input Range CMVR GND VCC V Common-Mode Rejection Ratio CMRR VCM = GND to VCC 0.03 1 V/mV

w w w . c o n s o n a n c e - e l e c . c o m 5 R e v 1 . 0 (Continued from last page) Parameters Symbol Test Conditions Mi n T y p M a x U n i t Power-Supply Rejection Ratio PSRR VCC = 2.5V to 5.5V 0.07 1.0 V/mV Output High V oltage V OH RL = 100k Ω to GND VCC－0.3V V Output Low V oltage V OL RL = 100k Ω to GND GND + 0.05 V Output Source Current I SRC VCC－GND= 5V 300 820 uA Output Sink Current I SNK VCC－GND= 5V 200 570 uA Detailed Description The CN951 is combinations of a low power op amp, comp arator and reference in an 8-pin SO package, as shown in Figure 2. In the CN951, the comparator’s negative input is connected to a 1.211V ±2% bandgap reference. The device is optimized to operate from a single supply. Op Amp The op amp in the CN951 is internal ly compensated to be unity-gain stable, 20V/ms slew rate. The op amp features high-impedance differential inputs and a co mmon mode input voltage range that extends from the negative supply rail to within the positive rail. The CMOS output stage can swing rail to rail and is driven by a proprietary high gain stage, which enables it to operate with a low supply current while maintaining linearity under loaded conditions. Careful design results in good DC characteristics over their entire operating temperature range, minimizing input referred errors. Comparator The comparator in the CN951 has a high impedance differential input stage with a common mode input voltage range that extends from the negative supply rail to the positive rail. The CMOS output stage swings rail-to-rail and can continuously source as much as 20mA. The comparator eliminates power-supply glitches that commonly occur when changing logic states, mini mizing parasitic feedback and making them easier to use. In addition, they include intern al ±7mV(14mV) hysteresis to ensure clean output switching, even with slow-moving input signals. The input can be taken above and below the supply rails up to 300mV without damage. Input voltages beyond this range can forward bias the ESD-protection diode and should be avoided. The CN951 comparator output can also swing rail to rail. TTL compatibility is assured by using a 5V ±10% supply. The CN951 comparator continuously outputs source currents or sink current as high as 20mA, while keeping quiescent currents in the microampere range. The output can source or sink 100mA (at VCC = 5V) for short pulses, as long as the package’s maximum power dissipation is not exceeded. The output stage does not generate crowbar switching currents during transitions; this minimizes feedback through the supplies and helps ensure stability without bypassing. Reference The internal reference in the CN951 has an output of 1.211V with respect to GND. Its accuracy is ±2% in the -40°C to +85°C temperature range. It is comprised of a trimmed bandgap reference fed by a proportional to absolute-temperature (PTAT) current source and buffered by a micropow er unity-gain amplifier. The REF output is typically capable of sourcing and sinking 20 μA. Do not bypass the refere nce output. The reference is stable for capacitive loads less than 100pF.

Application Information

Hysteresis increases the comparator’s noise immunity by increasing the upper threshold and decreasing the

w w w . c o n s o n a n c e - e l e c . c o m 7 R e v 1 . 0 R2’s value can be chosen between 1MΩ and 2MΩ for smaller supply current, then calculate RA and RB’s values based on the above 2 equations and the hysteresis needed. Input Noise Considerations Because low power requirements often demand high impedance circuits, effects from radiated noise are more significant. Thus, traces between the op amp or comparator inputs and any resistor networks attached should be kept as short as possible. Crosstalk-Reference There may be crosstalk to the reference from the comparator in the CN951. Applications using the reference for the op amp or external circuitry can eliminate this crosstalk by using a simple RC low-pass filter, as shown in Figure 5. In figure 5, R1 and C1 serve the purpose. Figure 5 RC Filter to Eliminate Crosstalk at REF Op Amp Stability and Board Layout Considerations The op amp in the CN951 maintains stability in their minimum gain configuration while driving heavy capacitive loads. Although this family is primarily designed for low frequency applications, good layout is extremely important. Low-power, high-impedance circuits may increase the effects of board leakage and stray capacitance. For example, the combination of a 10MΩ resistance (from leakage between traces on a contaminated, poorly designed PC board) and a 1pF stray capacitance provides a pole at approximately 16kHz, which is near the amplifier’s bandwidth. Board routing and layout should minimize leakage and stray capacitance. In some cases, stray capacitance may be unavoidable and it may be necessary to add a 2pF to 10pF capacitor across the feedback resistor to compensate; select the smallest capacitor value that ensures stability. Power-Supply Bypassing Power-supply bypass capacitor is not required if the supply impedance is low. For single-supply applications, it is good practice to bypass VCC with a 0.1μF capacitor to ground. Do not bypass the reference output.

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Package Information

Consonance does not assume any responsibility for use of any circuitry described. Consonance reserves the right to change the circuitry and specifications without notice at any time.