Advanced Linear Devices ALD2321ASCL

The ALD2321A/ALD2321B/ALD2321 is a monolithic Precision Dual Voltage Comparator, each having integrated dual complementary output drivers. It is constructed using advanced silicon gate CMOS technology. Key features include very high input impedance, very low offset voltage utilizing on-chip e-trim (EPAD electronic-trimming) technology, flexible multiple output configurations and fast response time with small overdrive voltage. It is designed for ultra low level signal detection from high impedance sources. For many applications it can eliminate an input amplification stage, a precision input bias stage, a signal level shift stage and an output buffer stage, and do the entire job from low level input signal detection to high output driver -- all on a single chip.

The input voltage includes ground, making this voltage comparator ideal for single supply (+5V) or dual supply (±5V) powered systems. For dual supply applications, GND pin is connected to the most negative supply instead of Ground (0.0V). The negative supply voltage can be at any value between 0.0V and -5V. Each voltage comparator is individually trimmed at the factory for minimum offset voltage at ground voltage potential, making it at its best offset voltage and ready to compare very low signal level voltages at or near ground potential. Typically a signal less than 1mV can be resolved and detected reliably without requiring amplification. Sensor or detector signals with signal power as low as 0.004pW (4×10⁻¹⁵ Watt) can be readily detected.

Each voltage comparator has two complementary output pins, one for Source Output (OUTH) and the other for Sink Output (OUT). This dual complementary output allows maximum circuit design flexibility. The outputs can be used as Single-Ended Driver, Multiple WIRED-OR Outputs, Push-Pull Outputs or Complementary Outputs. The Sink Output can be used as an open drain output, which has current sink capability of up to 50mA. It can also be connected to an external voltage higher or lower than V+, which provide level shift of the output swing levels from other than V+ to GND. The Source Output can source up to 2mA and can be used to drive the base terminal of an external NPN bipolar device or the gate of a Nchannel MOSFET device.

The two outputs, Source Output and Sink Output, can be connected together to form a push-pull output which has the combined output capabilities of both channels.

In the dual complementary output mode, each comparator can be used to drive separate loads. Due to the complementary nature of the two outputs, only one output is active at any a given time, except for a limited crossover time. When OUT (sink output) is active ON, the OUT pin is sinking current and the OUTH pin is OFF and in high impedance mode. Conversely, if OUTH pin is ON and sourcing current, OUT pin is OFF. To configure push-pull output, simply connect OUT (sink output) pin to OUTH pin.

Since each voltage comparator has its own complementary outputs, each comparator can be configured to have a different output type. For example, one comparator output can be connected as Open Drain output while the other comparator can be wired as push-pull output. If used to drive capacitive loads, the output DC current levels are at a very low level, at essentially leakage current levels, which can be a power saving feature.

The ALD2321A/ALD2321B/ALD2321 can detect and resolve very low voltage levels at high speed, with little or no overdrive voltage. Compared with other voltage comparator devices that require 100 mV overdrive voltages, or multiple stage circuits that include input preamp, etc., it can perform all input to output functions in one device with minimal delay time and with as low as a 1mV signal.

It is supplied with 4 external etrim pins, VE11, VE12, VE21, and VE22. These pins are used for trimming of the voltage comparator offset voltages at the factory, and normally should be left open unconnected. However, in some cases these pins can be used as positive/negative feedback pins, since these pins have a positive/negative factor on the offset voltage.

• Ultra low signal power of 4fW detectable
• Ultra low offset voltage of max. 0.2mV
• Ultra low input bias currents of typ. 0.01pA
• Low supply current of 110μA typical
• Virtually eliminates source impedance effects
• Low operating supply voltage of 4V to 10V
• Single (+5V) and dual supply (±5V) operation
• High speed for both small and large level signals 300ns typical for TTL inputs
• CMOS, NMOS and TTL compatible
• Each comparator has separate push and pull outputs
• High output sink current - typically 50mA
• Low supply current spikes
• Fanout of 30 TTL loads

• Dual limit window comparator
• Power supply voltage monitor
• Photo-detector sensor circuit
• Relay or LED driver
• Oscillators
• Battery operated instruments
• Remote signal detection