Datasheet LTC1841, LTC1842, LTC1843 (Analog Devices) - 7

LTC1841/LTC1842/LTC1843
U U W U APPLICATIONS INFORMATION
The LTC1841/LTC1842/LTC1843 are dual micropower REFERENCE OUTPUT comparators with a built-in 1.182V reference (LTC1842/ REF LTC1843). Features include programmable hysteresis, R1 LTC1843 wide supply voltage range (2V to 11V) and the ability for the reference to drive up to a 0.01µF capacitor without C1 oscillation. The comparators’ open-drain outputs can typi- V – cally sink greater than 20mA and the supply current glitches that normally occur when switching logic states 1841/43 F01 have been eliminated.
Figure 1. Damping the Reference Output Power Supplies
The comparators operate from a single 2V to 11V (2.5V to Figure 2 shows the resistor value required for different 11V for LTC1842/LTC1843) or dual ±1V to ±5.5V supply capacitor values to achieve critical damping. Bypassing (±1.25V to ±5.5V for LTC1842/LTC1843). If the reference the reference can help prevent false tripping of the com- output is required to source more than 1mA or the supply parators by preventing glitches on V + or reference load source impedance is high, V + should be bypassed with a transients from disturbing the reference output voltage. 0.1µF capacitor.
Comparator Inputs
100 The comparators’ input can swing from the negative supply V – to within 1.3V (max) of the positive supply V +. ) The input can be forced 300mV below V – or above V + Ω 10 without damage and the typical input leakage current is only ±10pA. 1
Comparator Outputs
RESISTOR VALUE (k Each comparator output is an open-drain pull-down to V– typically capable of sinking greater than 20mA. The low 0.1 output leakage current while in three-state mode allows a 0.001 0.01 0.1 1 10 CAPACITOR VALUE (µF) high value pull-up resistor to be used. The open-drain 1841/43 F02 outputs can be wire OR-ed or used in level shifting applications.
Figure 2. Damping Resistance vs Bypass Capacitor Value Voltage Reference
The internal bandgap reference has an output voltage of Figure 3 shows the bypassed reference output with a 1.182V referenced to V –. The reference accuracy is 1.5% square wave applied to the V + pin. Resistors R2 and R3 set from – 40°C to 85°C. It can typically source greater than a 10mV hysteresis voltage band while R1 damps the 1mA and sink up to 10µA with a 5V supply. The reference reference response. Note that the comparator output can drive a bypass capacitor of up to 0.01µF without doesn’t trip. oscillation. By inserting a series resistor, capacitance values up to 100µF can be used (Figure 1). 7