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UC1903 UC2903 UC3903
Quad Supply and Line Monitor
FEATURES
* * * * Inputs for Monitoring up to Four Separate Supply Voltage Levels Internal Inverter for Sensing a Negative Supply Voltage Line/Switch Sense Input for Early Power Source Failure Warning Programmable Under- and Over-Voltage Fault Thresholds with Proportional Hysteresis A Precision 2.5V Reference General Purpose Op-Amp for Auxiliary Use Three High Current, >30mA, Open-Collector Outputs Indicate Over-Voltage, Under-Voltage and Power OK Conditions Input Supply Under-Voltage Sensing and Start-Latch Eliminate Erroneous Fault Alerts During Start-Up 8-40V Supply Operation with 7mA Stand-By Current
DESCRIPTION
The UC1903 family of quad supply and line monitor integrated circuits will respond to under- and over-voltage conditions on up to four continuously monitored voltage levels. An internal op-amp inverter allows at least one of these levels to be negative. A separate line/switcher sense input is available to provide early warning of line or other power source failures. The fault window adjustment circuit on these devices provides easy programming of under- and over-voltage thresholds. The thresholds, centered around a precision 2.5V reference, have an input hysteresis that scales with the window width for precise, glitch-free operation. A reference output pin allows the sense input fault windows to be scaled independently using simple resistive dividers. The three open collector outputs on these devices will sink in excess of 30mA of load current when active. The under- and over-voltage outputs respond after separate, user defined, delays to respective fault conditions. The third output is active during any fault condition including under- and over-voltage, line/switcher faults, and input supply under-voltage. The off state of this output indicates a "power OK" situation. An additional, uncommitted, general purpose op-amp is also included. This op-amp, capable of sourcing 20mA of output current, can be used for a number of auxiliary functions including the sensing and amplification of a feedback error signal when the 2.5V output is used as a system reference. In addition, these ICs are equipped with a start-latch to prevent erroneous under-voltage indications during start-up. These parts operate over an 8V to 40V input supply range and require a typical stand-by current of only 7mA.
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BLOCK DIAGRAM
Note: Pin numbers refer to J, N and DW packages.
4/97
ABSOLUTE MAXIMUM RATINGS (Note 1)
Supply Voltage (+VIN). . . . . . . . . . . . . . . . . . . . . . . . . . . . . +40V Open Collector Output Voltages. . . . . . . . . . . . . . . . . . . . . +40V Open Collector Output Currents . . . . . . . . . . . . . . . . . . . . 50mA Sense 1-4 Input Voltages . . . . . . . . . . . . . . . . . . . -0.3V to +20V Line/Switcher Sense Input Voltage . . . . . . . . . . . -0.3V to +40V Op-Amp and Inverter Input Voltages . . . . . . . . . . -0.3V to +40V Op-Amp and Inverter Output Currents . . . . . . . . . . . . . . -40mA Window Adjust Voltage. . . . . . . . . . . . . . . . . . . . . 0.0V to +10V Delay Pin Voltages . . . . . . . . . . . . . . . . . . . . . . . . . 0.0V to +5V Reference Output Current . . . . . . . . . . . . . . . . . . . . . . . -40mA Power Dissipation at TA = 25C (Note 1) . . . . . . . . . . . 1000mW Power Dissipation at TC = 25C (Note 1) . . . . . . . . . . . 2000mW Operating Junction Temperature . . . . . . . . . . . -55C to +150C Storage Temperature . . . . . . . . . . . . . . . . . . . . -65C to +150C Lead Temperature (Soldering, 10 Seconds) . . . . . . . . . . 300C
UC1903 UC2903 UC3903
Note 1: Voltages are referenced to ground (Pin 3). Currents are positive into, negative out of, the specified terminals. Consult Packaging Section of Databook for thermal limitations and considerations of package.
CONNECTION DIAGRAMS
PLCC-20, LCC-20 (TOP VIEW) Q, L Package
PACKAGE PIN FUNCTION FUNCTION PIN
DIL-18, SOIC-18 (TOP VIEW) J or N, DW Package
+VIN VREF (2.5V) GROUND GROUND WINDOW ADJUST N/C SENSE 4 INVERT INPUT SENSE 4 SENSE 3 SENSE 2 SENSE 1 OV DELAY OV FAULT UV FAULT UV DELAY POWER OK LINE/SWITCHER SENSE G.P. OP-AMP OUT G.P. OP-AMP N.I. G.P. OP-AMP INV.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for TA = -55C to +125C for the
UC1903; -40C to +85C for the UC2903; and 0C to +70C for the UC3903; +VIN = 15V; Sense Inputs (Pins 6-9 and Pin 15) = 2.5V; VPIN 4 = 1.0V, TA = TJ. PARAMETERS Supply Input Supply Current Supply Under Voltage Threshold (VSUV) Minimum Supply to Enable Power OK Output Reference Output Voltage (VREF) Load Regulation Line Regulation Short Circuit Current Fault Thresholds (Note 4) OV Threshold Adj. UV Threshold Adj. Offset from VREF as a function of VPIN 4 Input = Low to High, 0.5V VPIN 4 2.5V Offset from VREF as a function of VPIN 4 Input = High to Low, 0.5V VPIN 4 2.5V .230 -.270 .25 -.25 .270 -.230 .230 -.270 .25 -.25 .270 -.230 V/V V/V TJ = 25C Over Temperature IL = 0 to 10mA +VIN = 8 to 40V TJ = 25C 2.485 2.465 1 1 40 2.5 2.515 2.535 10 4 2.470 2.465 1 1 40 2.5 2.530 2.535 15 8 V V mV mV mA No Faults UV, OV and Line Fault Fault Outputs Enabled 6.0 7 10 7.0 3.0 9 15 7.5 4.0 5.5 7 10 7.0 3.0 11 18 8.0 4.0 mA mA V V TEST CONDITIONS UC1903 / UC2903 MIN TYP MAX MIN UC3903 TYP MAX UNITS
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UC1903 UC2903 UC3903 ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for TA = -55C to +125C for the
UC1903; -40C to +85C for the UC2903; and 0C to +70C for the UC3903; +VIN = 15V; Sense Inputs (Pins 6-9 and Pin 15) = 2.5V; VPIN 4 = 1.0V, TA = TJ. PARAMETERS Fault Thresholds (cont.) OV & UV Threshold Hyst. 0.5V VPIN 4 2.5V 10 20 .002 1 1.94 125 Input = 2.8V (Note 2) Input = 2.2 (Note 2) Input = 2.3V (Note 2) 2.0 175 1 -1 1 30 .01 10 2.06 225 3 -3 3 1.9 100 10 20 .002 1 2.0 175 1 -1 1 30 .02 12 2.1 250 6 -6 6 mV/V %/V A/V V mV A A A OV & UV Threshold Supply +VIN = 8V to 40V Sensitivity Adjust Pin (Pin 4) Input Bias Current Line Sense Threshold Line Sense Threshold Hyst. Sense Inputs Sense 1-4 Input Bias Current Line Sense Input Bias Current OV and UV Fault Delay Charging Current Threshold Voltage Threshold Hysteresis Delay Delay Pin = Low to High TJ = 25C Ratio of Threshold Voltage to Charging Current VOUT = 2V IOUT = 12mA VOUT = 40 V 20 60 1.8 250 30 50 20 60 1.8 250 30 50 A V mV ms/F 0.5V VPIN 4 2.5V Input = High to Low TEST CONDITIONS UC1903/UC2903 MIN TYP MAX MIN UC3903 TYP MAX UNITS
Fault Outputs (OV, UV, & Power 0K) Maximum Current Saturation Voltage Leakage Current Sense 4 Inverter (Note 3) Input Offset Voltage Input Bias Current Open Loop Gain PSRR Unity Gain Frequency Slew Rate Short Circuit Current G.P. Op-Amp (Note 3) Input Offset Voltage Input Bias Voltage Input Offset Current Open Loop Gain CMRR PSRR Unity Gain Frequency Slew Rate Short Circuit Current TJ = 25C VCM = 0 to +VIN = 2.0V +VIN = 8 to 40V 65 65 65 1 .1 .01 120 100 100 1 .4 40 5 2 .5 65 65 65 1 .1 .01 120 100 100 1 .4 40 8 4 1.0 mV A A dB dB dB MHz V/s mA TJ = 25C +VIN = 8 to 40 V 65 65 2 .1 80 100 1 .4 40 8 2 65 65 2 .1 80 100 1 .4 40 10 4 mV A dB dB MHz V/s mA 30 70 .25 3 .40 25 30 70 .25 3 .40 25 mA V A
Note 2: These currents represent maximum input bias currents required as the sense inputs cross appropriate thresholds. Note 3: When either the G.P. OP-Amp, or the Sense 4 Inverter, are configured for sensing a negative supply voltage, the divider resistance at the inverting input should be chosen such that the nominal divider current is 1.4mA. With the divider current at or below this level possible latching of the circuit is avoided. Proper operation for currents at or below 1.4mA is 100% tested in production. Note 4: Reference to pin numbers in this specification pertain to 18 pin DIL N and J packages and 18 pin SOIC DW package.
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UC1903 UC2903 UC3903
Typical 2.5V Reference Temperature Characteristic Typical Fault Delay Temperature Characteristic (CDELAY 270pF)
OPERATION AND APPLICATION INFORMATION
Figure 1. The UC1903 fault window circuitry generates OV and UV thresholds centered around the 2.5V reference. Window magnitude and threshold hysteresis are proportional to the window adjust input voltage at Pin 4.
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OPERATION AND APPLICATION INFORMATION
Setting a Fault Window The fault thresholds on the UC1903 are generated by creating positive and negative offsets, equal in magnitude, that are referenced to the chip's 2.5V reference. The resulting fault window is centered around 2.5V and has a magnitude equal to that of the applied offsets. Simplified schematics of the fault window and reference circuits are shown in Figure 1 (see previous page). The magnitude of the offsets is determined by the voltage applied at the window adjust pin, Pin 4. A bias cancellation circuit keeps the input current required at Pin 4 low, allowing the use of a simple resistive divider off the reference to set the adjust pin voltage. The adjust voltage at Pin 4 is internally applied across R4, and an 8k resistor. The resulting current is mirrored four times to generate current sources IOA, IOB, IOC, and IOD, all equal in magnitude. When all four of the sense inputs are inside the fault window, a no-fault condition, Q4 and Q5 are turned on. In combination with D1 and D2 this prevents LOB and LOD from affecting the fault thresholds. In this case, the OV and UV thresholds are equal to VREF + IOA(R5 + R6) and VREF - IOC(R7 + R8) respectively. The fault window can be expressed as: (1) 2.5V VADJ . 4
UC1903 UC2903 UC3903
hysteresis at the sense inputs which is always 8% of the window magnitude. This is shown graphically in Figure 2. Fault Windows Can Be Scaled Independently In many applications, it may be desirable to monitor various supply voltages, or voltage levels, with varying fault windows. Using the reference output and external resistive dividers this is easily accomplished with the UC1903. Figures 3 and 4 illustrate how the fault window at any sense input can be scaled independently of the remaining inputs.
Fault window for the Sense Input, in percent, is: R3 + R1R2/(R1 + R2) 10 (VADJ) * ,
R3
for: VS (NOM) *
R2 = 2.5V R1 + R2
Figure 3. Using the reference output and a resistive divider, a
sense input with an independently wider fault window can be generated.
In terms of a sensed nominal voltage level, VS, the window as a percent variation is: (2) VS ( 10 VADJ) %.
When a sense input moves outside the fault window given in equation(1), the appropriate hysteresis control signal turns off Q4 or Q5. For the under-voltage case, Q5 is disabled and current source IOB flows through D2. The net current through R7 becomes zero as IOB cancels IOC, giving an 8% reduction in the UV threshold offset. The overvoltage case is the same, with Q4 turning off, allowing IOD to cancel the current flow, IOA, through R6. The result is a
Fault window for the sense input, in percent, is: 10 (VADJ) *
R2 R1 + R2
Figure 4. The general purpose op-amp on the UC1903 can be used to create a sense input with an independently tighter fault window. Figure 4 demonstrates one of many auxiliary functions that the uncommitted op-amp on the UC1903 can be used for. Alternatively, this op-amp can be used to buffer high impedance points, perform logic functions, or for sensing and amplification. For example, the G.P. op-amp, combined with the 2.5V reference, can be used to produce and buffer an optically coupled feedback signal in isolated supplies with primary side control. The output stage of this op-amp is detailed in Figure 5. The NPN emitter follower provides high source current capability. 20mA while the substrate device, Q3, provides good transient sinking capability. 5
Figure 2. The fault window and threshold hysteresis scale as a function of the voltage applied at Pin 4, the window adjust pin.
OPERATION AND APPLICATION INFORMATION (continued)
UC1903 UC2903 UC3903
SENSE input goes from above to below 2.0V. The line sense comparator has approximately 175mV of hysteresis requiring the line/switcher input to reach 2.175V before the POWER OK output device can be turned off, allowing a no-fault indication. In Figure 7 an example showing the use of the LINE/SWITCHER SENSE input for early switcher-fault detection is detailed. A sample signal is taken from the output of the power transformer, rectified and filtered, and used at the line/switcher input. By adjusting the R2C time constant with respect to the switching frequency of the supply and the hold up time of the output capacitor, switcher faults can be detected before supply outputs are significantly affected.
Figure 5. The G.P. op-amp on the UC1903 has a high source current (20mA) capability and enhanced transient sinking capability through substrate device Q3. Sensing a Negative Voltage Level The UC1903 has a dedicated inverter coupled to the sense 4 input. With this inverter, a negative voltage level can be sensed as shown in Figure 6. The output of the inverter is an unbiased emitter follower. By tying the inverting input, Pin 5, high the output emitter follower will be reverse biased, leaving the sense 4 input in a high impedance state. In this manner, the sense 4 input can be used, as the remaining sense inputs would be, for sensing positive voltage levels.
Figure 7. The line/switcher sense input can be used for an
early line or switcher fault indication.
OV and UV Comparators Maintain Accurate Thresholds The structure of the OV and UV comparators, shown in Figure 8 results in accurate fault thresholds even in the case where multiple sense inputs cross a fault threshold simultaneously. Unused sense inputs can be tied either to the 2.5V reference, or to another, utilized, sense input. The four under- and over-voltage sense inputs on the UC1903 are clamped as detailed on the Sense 1 input in Figure 8. The series 2k resistor, R1, and zener diode Z1, prevent extreme under- and over-voltage conditions from inverting the outputs of the fault comparators. A parasitic diode, D1, is present at the inputs as well. Under normal operation it is advisable to insure that voltage levels at all of the sense inputs stay above -0.3V. The same type of input protection exists at the line sense input, Pin 15, except a 5k series resistor is used. The fault delay circuitry on the UC1903 is also shown in Figure 8. In the case of an over-voltage condition at one of the sense inputs Q20 is turned off, allowing the internal 60A current source to charge the user-selected delay capacitor. When the capacitor voltage reaches 1.8V, the OV and POWER OK outputs become active low. When the fault condition goes away Q20 is turned back on, rapidly discharging the delay capacitor. Operation of the under-voltage delay is, with appropriate substitutions, the same.
Note: A similar scheme w/the G.P. op-amp will allow a second negative supply to be monitored. Figure 6. Inverting the sense 4 input for monitoring a negative supply is accommodated with the dedicated inverter.
Using The Line/Switcher Sense Output The line switcher sense input to the UC1903 can be used for early detection of line, switcher, or other power source, failures. Internally referenced to 2.0V, the line sense comparator will cause the POWER OK output to indicate a fault (active low) condition when the LINE/SWITCHER
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UC1903 UC2903 UC3903 OPERATION AND APPLICATION INFORMATION (continued)
Figure 8. The OV and UV comparators on the UC1903 trigger respective fault delay circuits when one or more of the sense inputs move outside the fault window. Input clamps insure proper operation under extreme fault conditions. Terminating the UV delay capacitor to VREF assures correct logic at power up. Start Latch and Supply Under-Voltage Sense Allow Predictable Power-Up The supply under-voltage sense and start-latch circuitry on the UC1903 prevents fault indications during start-up or low input supply (+VIN) conditions. When the input supply voltage is below the supply under-voltage threshold the OV and UV fault outputs are disabled and the POWER OK output is active low. The POWER OK output will remain active until the input supply drops below approximately 3.0V. With +VIN below this level, all of the open collector outputs will be off.
When the input supply is low, the under-voltage sense circuitry resets the start-latch. With the start-latch reset, the UV fault output will remain disabled until the input supply rises to its normal operating level (8-40V), and all of the sense inputs are above the under-voltage threshold. This allows slow starting, or supply sequencing, without an artificial under-voltage fault indication. Once the latch is set, the UV fault output will respond if any of the sense inputs drop below the under-voltage threshold.
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