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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 fam i l y of qu ad s up pl y a nd l ine monitor integrated circuits wil l respond to under- and over-voltage conditions on up to four continuously monitored volt age leve ls. An internal op-amp i nverte r allows at least one of these
levels to b e n egat iv e. A separate line/switcher sense input is available to provide early warning of line or other power source failures.
The fault window adjustment ci rcuit on these devices provides easy programming of un der- and ov er-voltage thr esholds. The thresholds, center ed around
a precision 2. 5V r e fe ren c e, ha ve a n i n pu t h y ste r esi s t ha t sc a l es with the window width for precise, glitch-free operation. A reference output pin allows the
sense input fault windo ws to be scal ed independen tly using simp le resistive
dividers.
The three open collector outputs on these devices will sink in excess of 30mA
of load current when activ e. The under- and over-voltage outputs respond after separate, user d efine d, d ela ys to r espect ive fa ult co nd itions. T h e t h ir d o u tput is active during any fault condition including under- and over-voltage,
line/switc her faul ts, and i nput sup ply unde r-volt age. The off s tate of this output indicates a "power OK" situation.
An additional, uncommitted, general purpose op-amp is also included. This
op-amp, capa ble of s ourc ing 20mA of output cu rr ent, 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.
BLOCK DIAGRAM
4/97
Note: Pin numbers refe r to J, N and D W pa ck ag es .
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UC1903
UC2903
UC3903
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 T
A
= 25°C (Note 1) . . . . . . . . . . . 1000mW
Power Dissipation at TC = 25°C (Note 1) . . . . . . . . . . . 2000mW
Operating Junction Temperature . . . . . . . . . . . -55°C to +150°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . -65°C to +150°C
Lead Temperature (Soldering, 10 Seconds) . . . . . . . . . . 300°C
CONNECTION DIAGRAMS
DIL-18, SOIC-18 (TOP VIEW)
J or N, DW Package
PACKAGE PIN FUNCTION
FUNCTION PIN
+VIN 1
V
REF
(2.5V) 2
GROUND 3
GROUND 4
WINDOW ADJUST 5
N/C 6
SENSE 4 INVERT
INPUT
7
SENSE 4 8
SENSE 3 9
SENSE 2 10
SENSE 1 11
OV DELAY 12
OV FAULT 13
UV FAULT 14
UV DELAY 15
POWER OK 16
LINE/SWITCHER
SENSE
17
G.P. OP-AMP OUT 18
G.P. OP-AMP N.I. 19
G.P. OP-AMP INV. 20
PLCC-20, LCC-20
(TOP VIEW)
Q, L Package
ELECTRICAL CHARACTERISTICS:
Unless otherwise st ated, these specif ic at io ns app ly f or TA = –55°C to +125°C for the
UC1903; –40°C to +85°C for the UC2903; and 0°C to +70°C for the UC3903; +VIN =
15V; Sense Inputs (Pins 6–9 an d Pin 15) = 2. 5V; V
PIN 4
= 1.0V, TA = T
J.
PARAMETERS TEST CONDITIONS UC1903 / UC2903 UC3903 UNITS
MIN TYP MAX MIN TYP MAX
Supply
Input Supply Current No Faults 7 9 7 11 mA
UV, OV and Line Fau lt 10 15 10 18 mA
Supply Under Voltage
Threshold (V
SUV
)
Fault Outputs Enabled 6.0 7.0 7.5 5.5 7.0 8.0 V
Minimum Supply to Enable
Power OK Output
3.0 4.0 3.0 4.0 V
Reference
Output Voltage (V
REF
)T
J
= 25°C 2.485 2.5 2.515 2.470 2.5 2.530 V
Over Temperatur e 2.465 2.535 2.465 2.535 V
Load Regulation I
L
= 0 to 10mA 1 10 1 15 mV
Line Regulation +V
IN
= 8 to 40V 1 4 1 8 mV
Short Circuit Current TJ = 25°C 40 40 mA
Fault Thresholds (Note 4)
OV Threshold Adj. Offset from V
REF
as a function of V
PIN 4
Input = Low to High, 0.5V ≤ V
PIN 4
≤ 2.5V
.230 .25 .270 .230 .25 .270 V/V
UV Threshold Adj. Offset from V
REF
as a function of V
PIN 4
Input = High to Low, 0.5V ≤ V
PIN 4
≤ 2.5V
-.270 -.25 -.230 -.270 -.25 -.230 V/V
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Note 1: Voltages are referenced to gro un d (Pin 3) . Curren ts
are positive into, negative out of, the specified terminals.
Consult Packaging Section of Databook for thermal
limitations and considerations of package.
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ELECTRICAL CHARACTERISTICS:
PARAMETERS TEST CONDITIONS UC1903/UC2903 UC3903 UNITS
MIN TYP MAX MIN TYP MAX
Fault Thresholds (cont.)
OV & UV Threshold Hyst. 0.5V ≤ V
PIN 4
≤ 2.5V 10 20 30 10 20 30 mV/V
OV & UV Threshold Supply
Sensitivity
+VIN = 8V to 40V .002 .01 .002 .02 %/V
Adjust Pin (Pin 4)
Input Bias Current
0.5V ≤ V
PIN 4
≤ 2.5V ±1 ±10 ±1 ±12 µA/V
Line Sense Threshold Input = High to Low 1.94 2.0 2.06 1.9 2.0 2.1 V
Line Sense Threshold Hyst. 125 175 225 100 175 250 mV
Sense Input s
Sense 1-4
Input Bias Current
Input = 2.8V (Note 2) 1 3 1 6 µA
Input = 2.2 (Note 2) -1 -3 -1 -6
µ
A
Line Sense Input
Bias Current
Input = 2.3V (Note 2) 1 3 1 6
µ
A
OV and UV Fault Delay
Charging Current 60 60 µA
Threshold Voltage Delay Pin = Low to High 1.8 1.8 V
Threshold Hysteresis T
J
= 25°C 250 250 mV
Delay Ratio of Threshold Voltage to Charging
Current
20 30 50 20 30 50 ms/µF
Fault Outputs (
OV, UV, & Power 0K)
Maximum Curre nt V
OUT
= 2V 30 70 30 70 mA
Saturation Voltage I
OUT
= 12mA .25 .40 .25 .40 V
Leakage Current V
OUT
= 40 V 3 25 3 25 µA
Sense 4 Inverter (Note 3)
Input Offset Voltage 2 8 2 10 mV
Input Bias Current .1 2 .1 4 µA
Open Loop Gain 65 80 65 80 d B
PSRR +V
IN
= 8 to 40 V 65 100 65 100 dB
Unity Gain Frequency 1 1 MHz
Slew Rate .4 .4 V/µs
Short Circuit Current T
J
= 25°C 40 40 mA
G.P. Op-Amp (Note 3)
Input Offset Voltage 1 5 1 8 mV
Input Bias Voltage .1 2 .1 4
µ
A
Input Offset Current .01 .5 .01 1.0 µA
Open Loop Gain 65 120 65 120 dB
CMRR V
CM
= 0 to +VIN = 2.0V 65 100 65 100 dB
PSRR +VIN = 8 to 40V 65 100 65 100 dB
Unity Gain Frequency 1 1 MHz
Slew Rate .4 .4 V/µs
Short Circuit Current T
J
= 25°C 40 40 mA
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 volta ge , th e di vi de r
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 produc ti on.
Note 4: Reference to pin numbers in this specification per tain to 18 pin DIL N and J packag es and 18 pin SOIC DW package.
UC1903
UC2903
UC3903
Unless otherwise st ated, these specif ic at io ns app ly f or TA = –55°C to +125°C for the
UC1903; –40°C to +85°C for the UC2903; and 0°C to +70°C for the UC3903; +VIN =
15V; Sense Inputs (Pins 6–9 an d Pin 15) = 2. 5V; V
PIN 4
= 1.0V, TA = T
J.
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UC1903
UC2903
UC3903
Typical 2.5V Reference
Temperature Characteristic
Typical Fault Delay
Temperature Characteristic (C
DELA Y
≥ 270pF)
OPERATION AND APPLICATION INFORMATION
Figure 1.
The UC1903 fault window cir cuitry 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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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 e qual to that of the applied offsets. Simplified
schematic s of the f ault wind ow and re ference circuits are
shown in Figu re 1 (see pre viou s pa ge). The magnitude of
the offsets is determined by the voltage applied at the
window adj u s t pi n , P i n 4. A bias cancellation c ircui t keeps
the input cur rent required a t P in 4 low, allowing the use of
a simple resi stive divider off the reference to set the adjust pin voltage.
The adjust voltage at Pin 4 is internally applied across R
4
,
and an 8k res istor. The resulting current is mirrored four
times to gene rate current sources I
OA
, IOB, IOC, and IOD,
all equal in magnitude. W hen all four of the sense inputs
are inside the fault window, a no-faul t condition, Q
4
and
Q
5
are turned on. In combination with D1 and D2 this pre-
vents L
OB
and L
OD
from affecting the fau lt thresholds. In
this case , the OV and UV threshol ds are equal to V
REF
+
I
OA(R5
+ R6) and V
REF
- IOC(R7 + R8) respectively. The
fault window can be expressed as:
(1) 2.5V ±
V
ADJ
4
.
In terms of a sensed nominal voltage level, V
S,
the win-
dow as a percent variation is:
(2) V
S
± ( 10 ⋅ V
ADJ
)
%.
When a sense input moves outside the fault window given
in equation(1), the appropriate hysteresis control signal
turns off Q
4
or Q5. For the und er-voltage case, Q5 is dis-
abled and cu rrent source I
OB
flows through D2. The net
current through R
7
becomes zero as IOB cancels IOC, giving an 8% reduction in the UV threshold offset. The overvoltage case is the same, with Q
4
turning off, allowing I
OD
to cancel the c urrent flow, IOA, through R6. The result is a
UC1903
UC2903
UC3903
Figure 2.
The fault window and threshold hysteresis scale as a
function of the voltage applied at Pin 4, the window adjust pin.
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 3.
Using the reference output and a resistive divider, a
sense input with an independently wider fault window can be
generated.
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 am pl i f i cation. For examp l e, 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, Q
3
, provides good
transient sinking capability.
Fault window for the Sense Input,
in percent, is:
±
10 (V
ADJ
) •
R3 + R1R2/
(
R1
+
R
2
)
R
3
,
for:
V
S (NOM
)
•
R
2
R1 + R
2
= 2.5V
Fault window for the sense input, in percent, is:
±
10 (V
ADJ
) •
R
2
R1 + R
2
OPERATION AND APPLICATION INFORMATION
hysteresis at the se nse inputs which is always 8% of the
window magnitude. This is shown graphically in Figure 2.
Fault Windows Can Be Scaled Independently
In many appli cations, 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 ea s i ly a c c om pl is h ed with the UC1903.
Figures 3 and 4 illustrate how the fault window at any
sense input c an be sc al e d i nd ep endentl y of the remaining
inputs.
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UC1903
UC2903
UC3903
Sensing a Negative Voltage Level
The UC1903 has a dedicated inverter coupled to the
sense 4 in put. Wi th thi s inverte r, a negative volt age 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.
Using The Line/Switcher Sense Output
The line sw i tc h er sen s e i np ut to the UC1903 c an be used
for early detection of line, switcher, or other power source,
failures. Internally referen ced to 2.0V, the line sense com parator will cause the POWER OK output to indicate a
fault (active low) condition when the LINE/SWITCHER
SENSE input goes from above to below 2.0V. The line
sense compa rator 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 R
2
C time constant with respect to the
switching fr eque ncy of t he s upp ly and the hold up time of
the output capacitor, switcher faults can be detected before supply outputs are significantly affected.
OV and UV Comparators Maintain Accurate
Thresholds
The structure of the
OV and UV comparato rs, shown in
Figure 8 resul ts in accurate fault thresholds even in the
case where multiple sense inputs cross a fault threshold
simultaneo us ly. 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, R
1
, and zener diode Z1,
prevent ext reme under- and ov er-voltage conditions from
inverting the outputs of the fault comparators. A parasitic
diode, D
1
, is present at t he inputs as well. Under normal
operation i t i s advi sable to insure that voltage l evels at al l
of the sen se inputs stay ab ove -0.3V. The same type of
input prote ctio n exis ts a t the line s ense input, Pin 15, ex cept a 5k series resistor is used.
The fault del ay circuitr y on the UC19 03 is also sho wn in
Figure 8. In th e case of an over-voltage condition at one
of the sense inputs Q
20
is turned off, a ll owi ng the internal
60µA 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 Q
20
is turned back on, rapidly discharging the delay capaci tor. Operation of the under-voltage delay is, with appropriate substitutions, the
same.
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.
Figure 7.
The line/switcher sense input can be used for an
early line or switcher fault indication.
Figure 6.
Inverting the sense 4 input for monitoring a negative
supply is accommodated with th e dedicated inverter.
Note: A similar scheme w/the G.P. op-amp will allow a second negative supply to be monitored.
OPERATION AND APPLICATION INFORMATION
(continued)
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UC1903
UC2903
UC3903
OPERATION AND APPLICATION INFORMATION
(continued)
UNITRODE CORPORATI ON
7 CONTINENTAL BLVD. • MERRIMACK, NH 03054
TEL. (603) 424- 24 10 • FAX (603) 424-3460
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 i ndications duri ng start-up
or low input supply (+V
IN
) 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 ou tp ut i s active low. The POWER OK output
will remain active until the input supply drops below approximately 3.0V. With +V
IN
below this level, all of the
open collector outputs will be off.
When the input supply is low, the under-voltage sense circuitry resets th e start-latc h. With the start-latch reset, the
UV fault outp ut will remain d isabled until the input supply
rises to its normal o perating level (8-40V), and all of the
sense inputs are above the under-voltage threshol d. This
allows slow starting, or supply s equencing, without an artificial under-voltage fault indication. Once the latch is set,
the UV fault out put will respond if any of the sense inputs
drop below the under-voltage threshold.
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 V
REF
assures correct logic at power up.
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