UCC1926
UCC2926
UCC3926
SLUS266A - OCTOBER 1999
FEATURES
Integral Non-inductive Current Sense
Element with Internal Kelvin
Connections
20A Current Rating
Bi-directional, High Side or Low Side
Sensing
Internal Temperature Nulling Circuitry
for Current Sense Element and
Amplifier
Logic Compatible Current Direction
Status Output
Low Offset, Chopper Stabilized
Current Sense Amplifier
Uncommitted Amplifier with User
Programmable Gain
Overcurrent Indication with User
Programmable Threshold
DESCRIPTION
The UCC3926 Current Sensor IC contains a wideband, transimpedance
amplifier for converting the current through an internal, non-inductive
1.3m
shunt resistor into a proportional voltage. The sense element oper-
ates in both high-side (V
DD
referenced) and low-side (GND referenced) ap-
plications.
The UCC3926 can measure currents up to
20A. This transimpedance am-
plifier gain is precisely trimmed to 33.3m
to convert a 15A input into a
500mV output signal. It has a very low input offset voltage from chop-
per-stabilization. A cross-switching block rectifies the input signal by forcing
the differential output, AOP positive with respect to the other differential
output, AON. SIGN indicates the polarity of the current.
The UCC3926 programmable amplifier provides three functions. It converts
the differential transimpedance output signal into a single-ended signal. It
has a user-controlled gain stage that sets the maximum current level to the
desired voltage and it level shifts the zero current point to the desired level
as well. A comparator then compares the output of the instrumentation am-
plifier to a user-set reference voltage on OCREF, which provides an
overcurrent status bit OC.
The UCC3926 is available in the 16 pin SOIC package.
20A Integrated Current Sensor
BLOCK DIAGRAM
UDG-97139-1
application
INFO
available
2
UCC1926
UCC2926
UCC3926
ABSOLUTE MAXIMUM RATINGS
Input Sense Current (I
IN
) . . . . . . . . . . . . . . . . . . . . . . . . . 20A
Supply Voltage, VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5V
Inrush Current, 50
s . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100A
Input Voltage Range (CSP, CSN) . . . . . . . . . . . 0.2V to 14.5V
CSP, CSN, Common Mode Range
(referenced to GND) . . . . . . . . . . . . . . . . . . . . . . . . . 200mV
CSP, CSN, Common Mode Range
(referenced to V
DD
) . . . . . . . . . . . . . . . . . . . . . . . . . . 200mV
Shunt Resistance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.25m
Storage Temperature . . . . . . . . . . . . . . . . . . . . 65C to 150C
Junction Temperature . . . . . . . . . . . . . . . . . . . . 55C to 150C
Lead Temperature (Soldering, 10sec.) . . . . . . . . . . . . . . 300C
Currents are positive into, negative out of the specified termi-
nal. Consult Packaging Section of Databook for thermal limita-
tions and considerations of packages.
ELECTRICAL CHARACTERISTICS:
Unless otherwise stated, these specifications apply for V
DD
= 4.8V; all temperature
ranges and T
A
= T
J
.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Supply Section
VDD
4.8
14
V
I
VDD
3.8
6
mA
Transimpedance Amplifier Section
AOP AON
I
IN
= 15A, VDD = 10V, 25C
490
500
510
mV
I
IN
= 15A, VDD = 10V, 0C to +70C
480
500
520
mV
I
IN
= 15A, VDD = 10V, 40C to +85C
460
500
540
mV
I
IN
= 15A, VDD = 10V, 55C to +125C
410
500
590
mV
Quiescent Output Voltage (AOP, AON)
I
IN
= 0
1.0
V
Quiescent Differential Voltage (AOP
AON)
I
IN
= 0, Measure AC Peak to Peak
0
30
mV
Bandwidth
(Note 1)
20
40
MHz
Output Impedance
350
500
Shunt Resistance
CSP to CSN
1.3
m
PSRR
VDD = 4.8V to 10V
45
dB
VDD = 10V to 14V
25
dB
Temperature Coefficient
(Note 1)
200
200
ppm/C
Sign Comparator Section
V
OH
, VDD SIGN
CSP = 1A, I
SIGN
= 100
A, CSN = 0V
0.2
0.4
V
V
OL
, SIGN
CSP = 1A, I
SIGN
= 100
A, CSN = 0V
0.2
0.4
V
I
IH
Threshold
Ramp CSP, CSN = 0V
400
700
mA
I
IL
Threshold
Ramp CSP, CSN = 0V
400
700
mA
Programmable Amplifier Section
A
VOL
60
70
dB
GBW
At 200kHz
6
13
MHz
V
IO
V
IN
= 0.5V, 1.5V, 2.5V
9
9
mV
CONNECTION DIAGRAM
SOIC-16 (Top View)
DS Package
ORDERING INFORMATION
TEMPERATURE RANGE
PACKAGES
UCC1926
55C to +125C
DS
UCC2926
40C to +85C
DS
UCC3926
0C to +70C
DS
3
UCC1926
UCC2926
UCC3926
ELECTRICAL CHARACTERISTICS:
Unless otherwise stated, these specifications apply for V
DD
= 4.8V; all temperature
ranges and T
A
= T
J
.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
Programmable Amplifier Section (cont.)
PSRR
V
DD
= 4.8V to 10V
60
dB
V
DD
= 10V to 14V
60
dB
Common Mode Input Range
0.5
2.5
V
I
IB
, Input Bias Current (NI, INV)
100
350
nA
I
IO
, Input Offset Current
20
350
nA
V
OL
INV NI = 20mV, IO = 0
A
100
200
mV
INV NI = 20mV, IO = 200
A
150
300
mV
V
OH
NI INV = 20mV, IO = 200
A, (VDD OUT)
1.2
2
V
V
OH
, Clamp
NI INV = 20mV, VDD = 14V
6
7
8
V
I
OL
OUT = 1.5V
1
3.5
mA
I
OH
OUT = 1.5V
250
325
mA
Overcurrent Comparator Section
OC Comp Threshold
OCREF = 2V
2.00
2.05
V
Common Mode Range
(Note 1)
0.1
V
DD
2
V
Hysteresis
20
40
60
mV
VOL
(OCREF OUT) = 100mV, IOC = 100
A
0.2
0.4
V
VOH, VDD OC
(OUT OCREF) = 100mV, IOC = 100
A
0.2
0.4
V
Propagation Delay
(OUT OCREF) =
100mV
90
175
ns
Note 1: Guaranteed by design. Not 100% tested in prodcution.
PIN DESCRIPTIONS
AOP: Positive output of the converted current signal.
Voltage from AOP to AON is the absolute value of the
transimpedance amplifier output. AOP may show some
"chopping"
noise.
The
differential
to
single-ended
conversion removes the common-mode noise between
AOP and AON.Some high frequency filtering of AOP to
GND can reduce the fast transient spikes. The output
stage of AOP is shown in Figure 1.
AON: Negative output of the converted current signal.
Voltage from AOP to AON is the absolute value of the
transimpedance amplifier output. AON may show some
"chopping"
noise.
The
differential
to
single-ended
conversion removes the common-mode noise between
AOP and AON. Some high frequency filtering of AON to
GND can reduce the fast transient spikes. Note that AON
is above GND voltage. The output stage of AON is shown
in Figure 1.
CSN: Input connection to one end of the internal current
sense shunt resistor. Nominal resistance from CSP to
CSN is 1.3m
. The current shunt has a nominal
temperature coefficient of 3530 ppm/C. The temperature
adjusted autozero gain is designed to cancel this temp
co. effect. CSN may be referenced to GND for low side
sensing or to VDD for high side sensing. CSP CSN
may vary from 75mV from either GND or VDD. Current
into CSN is defined as negative.
CSP: Input connection to the other end of the internal
current sense shunt resistor. Nominal resistance from
CSP to CSN is 1.3mW. The current shunt has a nominal
temperature coefficient of 3530 ppm/C. The temperature
adjusted autozero gain should cancel this temp co. effect.
CSP may be referenced to GND for low side sensing or
to VDD for high side sensing. CSP CSN may vary from
75mV from either GND or VDD. Current into CSP is
defined as positive.
15K
100
AOP, AON
VDD
250
A
ESD DIODE
CROSS SWITCH
IMPEDANCE
Figure 1. AOP and AON output stage.
4
UCC1926
UCC2926
UCC3926
GND: This pin is the return point for all device currents.
INV: Negative input to the programmable amplifier to
provide differential to single-ended signal conversion.
NI: Positive input to the programmable amplifier to
provide differential to single-ended signal conversion.
OC: Overcurrent comparator output. When OUT is
greater than OCREF, OC switches high. The OC
comparator has a typical hysteresis of 25mV.
OCREF: The reference pin of overcurrent comparator for
setting overcurrent threshold voltage.
OUT: Output of the programmable amplifier intended to
provide differential to single-ended signal conversion of
the transimpedance amplifier's outputs.
Use this opamp to establish overall gain and nominal
zero current reference voltage. This amplifier may be
configured with a gain of one or more. Any non-common
mode "chopping" noise between AOP and AON will show
up at OUT. Some filtering of OUT may improve the appli-
cation's performance.
SIGN: Sign comparator output. SIGN also controls the
analog switches in the cross-switching block to keep
AOP greater than AON. At currents near zero amps, the
sign comparator may switch from "chopping" noise from
the transimpedance amplifier.
VDD: VDD is the power input connection for this device.
Its input range is from 4.8V to 14V. Bypass to GND using
good quality ceramic capacitors.
PIN DESCRIPTIONS (cont.)
0
100
200
300
400
500
600
700
-20
-15
-10
-5
0
5
10
15
20
INPUT CURRENT [A]
OUTPUT
[mV]
LIMIT OF RESOLUTION
(SIGN LIMIT
THRESHOLD BAND)
Figure 2. Differential output voltage (AOP-AON) vs.
input current (I
IN
).
TYPICAL CHARACTERISTICS CURVES
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
-75
-50
-25
0
25
50
75
100
125
TEMPERATURE [C]
Q
U
IESCENT
O
UTPUT
V
OL
T
A
GE
[V]
Figure 3. Quiescent AOP, AON output voltage vs.
temperature.
480
500
520
540
560
580
600
620
-75
-50
-25
0
25
50
75
100
125
TEMPERATURE [C]
OUTPUT
V
O
L
T
A
G
E
[
mV]
VDD = 14V
VDD = 12V
VDD = 10V
VDD = 4.8V
I
IN
= 15A
Figure 4. Differential output voltage (AOP - AON) vs.
VDD and temperature.
0.800
0.900
1.000
1.100
1.200
1.300
1.400
1.500
1.600
1.700
1.800
-75
-50
-25
0
25
50
75
100
125
TEMPERATURE [C]
R
SHUNT
[m
]
Figure 5. Typical shunt resistance vs. temperature.
5
UCC1926
UCC2926
UCC3926
UNITRODE CORPORATION
7 CONTINENTAL BLVD. MERRIMACK, NH 03054
TEL. (603) 424-2410 FAX (603) 424-3460
9
2
3
6
+
CROSS
SWITCH
5
12
11
100pF
+
1.3m
I
MAX
=20A
14
1
TRANSIMPENDANCE
AMPLIFIER rm=3.33m
15
16
7
8
PROGRAMMABLE AMPLIFIER
SIGN COMPARATOR
SEL
OVERCURRENT
COMPARATOR
OUT
10k
10k
10k
SW3
10k
SW4
100pF
10
SW2
10k
10k
10k
SW1
0.027
F
1k
1k
+5V
1k
1k
+5V
0.027
F
1k
V
S
13
4
10k
0.027
F
10
F
10
PULSE
GENERATOR
VDD GND
+10V
LAB EVALUATION CIRCUIT
The circuit shown uses a pulse generator to switch cur-
rents while observing the analog voltage of the sensed
current. A four position switch can be used to experiment
with different gain settings for the programmable ampli-
fier. The OCREF voltage and the NI DC bias voltage can
be adjusted with 1k
potentiometers to offset the ampli-
fier output and set the overcurrent comparator threshold.
UDG-97158
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Copyright
2000, Texas Instruments Incorporated
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