LT1970
500mA Power Op Amp with
Adjustable Precision Current Limit
FeaTures
n
n
DescripTion
The
LT
®
1970
is a ± 500mA power op amp with precise
externally controlled current limiting. Separate control
voltages program the sourcing and sinking current limit
sense thresholds with 2% accuracy. Output current may
be boosted by adding external power transistors.
The circuit operates with single or split power supplies
from 5V to 36V total supply voltage. In normal operation,
the input stage supplies and the output stage supplies are
connected (V
CC
to V
+
and V
EE
to V
–
). To reduce power
dissipation it is possible to power the output stage (V
+
,
V
–
) from independent, lower voltage rails. The amplifier is
unity-gain stable with a 3.6MHz gain bandwidth product
and slews at 1.6V/µs. The current limit circuits operate
with a 2MHz response between the VC
SRC
or VC
SNK
control
inputs and the amplifier output.
Open collector status flags signal current limit circuit
activation, as well as thermal shutdown of the amplifier.
An enable logic input puts the amplifier into a low power,
high impedance output state when pulled low. Thermal
shutdown and a ±800mA fixed current limit protect the
chip under fault conditions.
The LT1970 is packaged in a 20-lead TSSOP package with
a thermally conductive copper bottom plate to facilitate
heat sinking.
n
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n
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± 500mA Minimum Output Current
Independent Adjustment of Source and
Sink Current Limits
2% Current Limit Accuracy
Operates with Single or Split Supplies
Shutdown/Enable Control Input
Open Collector Status Flags:
Sink Current Limit
Source Current Limit
Thermal Shutdown
Fail Safe Current Limit and Thermal Shutdown
1.6V/µs Slew Rate
3.6MHz Gain Bandwidth Product
Fast Current Limit Response: 2MHz Bandwidth
Specified Temperature Range: –40°C to 85°C
Available in a 20-Lead TSSOP Package
applicaTions
n
n
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Automatic Test Equipment
Laboratory Power Supplies
Motor Drivers
Thermoelectric Cooler Driver
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Typical applicaTion
V
LIMIT
0V TO 5V
A
V
= 2 Amplifier with Adjustable ± 500mA Full-Scale
Current Limit and Fault Indication
15V
V
LIMIT
10 • R
CS
15V
3k
Current Limited Sinewave Into 10Ω Load
I
OUT(LIMIT)
= ±
V
IN
4V
2V
V
LOAD
0V
I
OUT
R
CS
1
1/4W
–2V
V
CC
V
+
EN
VC
SRC
+IN
VC
SNK
ISNK
ISRC
TSD
LT1970
OUT
SENSE
+
SENSE
–
V
–
–IN
V
EE
COMMON
R1
10k
R2
10k
1970 TA01
LOAD
VC
SRC
= 4V
VC
SNK
= 2V
R
CS
= 1Ω
20µs/DIV
1970 TA02
–15V
1970fe
For more information
www.linear.com/LT1970
1
LT1970
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
V
EE
V
–
OUT
SENSE
+
FILTER
SENSE
–
V
CC
–IN
+IN
1
2
3
4
5
6
7
8
9
21
20 V
EE
19 V
+
18
TSD
17
ISNK
16
ISRC
V
EE
10
FE PACKAGE
20-LEAD PLASTIC TSSOP
T
JMAX
= 150°C,
θ
JA
= 40°C/W (NOTE 8)
EXPOSED PAD (PIN 21) IS CONNECTED TO V
EE
orDer inForMaTion
LEAD FREE FINISH
LT1970CFE#PBF
LT1970IFE#PBF
TAPE AND REEL
LT1970CFE#TRPBF
LT1970IFE#TRPBF
PART MARKING*
LT1970CFE
LT1970IFE
PACKAGE DESCRIPTION
20-Lead Plastic TSSOP
20-Lead Plastic TSSOP
SPECIFIED TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
elecTrical characTerisTics
SYMBOL
V
OS
PARAMETER
Input Offset Voltage
Power Op Amp Characteristics
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. See Test Circuit for standard test conditions.
CONDITIONS
MIN
TYP
200
l
l
l
0°C < T
A
< 70°C
–40°C < T
A
< 85°C
V
CM
= 0V
V
CM
= 0V
0.1Hz to 10Hz
1kHz
1kHz
Input Offset Voltage Drift (Note 4)
I
OS
I
B
e
n
i
n
Input Offset Current
Input Bias Current
Input Noise Voltage
Input Noise Voltage Density
Input Noise Current Density
l
l
2
For more information
www.linear.com/LT1970
+ –
–10
–100
–600
Supply Voltage (V
CC
to V
EE
) ..................................... 36V
Positive High Current Supply (V
+
)................... V
–
to V
CC
Negative High Current Supply(V
–
) ....................V
EE
to V
+
Amplifier Output (OUT) ..................................... V
–
to V
+
Current Sense Pins
(SENSE
+
, SENSE
–
, FILTER) ........................... V
–
to V
+
Logic Outputs (ISRC,
ISNK, TSD)
....... COMMON to V
CC
Input Voltage (–IN, +IN) ............ V
EE
– 0.3V to V
EE
+ 36V
Input Current......................................................... 10mA
Current Control Inputs
(VC
SRC
, VC
SNK
) .............. COMMON to COMMON + 7V
Enable Logic Input .............................. COMMON to V
CC
COMMON ....................................................... V
EE
to V
CC
Output Short-Circuit Duration ......................... Indefinite
Operating Temperature Range (Note 2)....–40°C to 85°C
Specified Temperature Range (Note 3) .... –40°C to 85°C
Maximum Junction Temperature.......................... 150°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
15 ENABLE
14 COMMON
13 VC
SRC
12 VC
SNK
11 V
EE
MAX
600
1000
1300
10
100
UNITS
µV
µV
µV
µV/°C
nA
nA
µV
P-P
nV/√Hz
pA/√Hz
1970fe
–4
–160
3
15
3
LT1970
elecTrical characTerisTics
SYMBOL
R
IN
C
IN
V
CM
CMRR
PSRR
PARAMETER
Input Resistance
Input Capacitance
Input Voltage Range
Common Mode Rejection Ratio
Power Supply Rejection Ratio
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. See Test Circuit for standard test conditions.
CONDITIONS
Common Mode
Differential Mode
Pin 8 and Pin 9 to Ground
Typical
Guaranteed by CMRR Test
–12V < V
CM
< 12V
V
EE
= V
–
= –5V, V
CC
= V
+
= 3V to 30V
V
EE
= V
–
= –5V, V
CC
= 30V, V
+
= 2.5V to 30V
V
EE
= V
–
= –3V to – 30V, V
CC
= V
+
= 5V
V
EE
= –30V, V
–
= –2.5V to –30V, V
CC
= V
+
= 5V
R
L
= 1k, –12.5V < V
OUT
< 12.5V
l
l
l
l
l
l
l
MIN
TYP
500
100
6
MAX
UNITS
kΩ
kΩ
pF
–14.5
–12.0
92
90
110
90
110
100
75
80
40
20
5
105
100
130
100
130
150
120
45
13.6
12.0
V
V
dB
dB
dB
dB
dB
V/mV
V/mV
V/mV
V/mV
V/mV
V/mV
A
VOL
Large-Signal Voltage Gain
R
L
= 100Ω, –12.5V < V
OUT
< 12.5V
l
R
L
= 10Ω, –5V < V
OUT
< 5V, V
+
= – V
–
= 8V
l
V
OL
V
OH
I
SC
SR
FPBW
GBW
t
S
Output Sat Voltage Low
V
OL
= V
OUT
– V
–
R
L
= 100, V
CC
= V
+
= 15V, V
EE
= V
–
= –15V
R
L
= 10, V
CC
= – V
EE
= 15V, V
+
= –V
–
= 5V
V
OH
= V
+
– V
OUT
R
L
= 100, V
CC
= V
+
= 15V, V
EE
= V
–
= –15V
R
L
= 10, V
CC
= – V
EE
= 15V, V
+
= –V
–
= 5V
Output Low, R
SENSE
= 0Ω
Output High, R
SENSE
= 0Ω
–10V < V
OUT
< 10V, R
L
= 1k
V
OUT
= 10V
PEAK
(Note 5)
f = 10kHz
0.01%, V
OUT
= 0V to 10V, A
V
= –1, R
L
= 1k
VC
SRC
= VC
SNK
= 0V
l
1.9
0.8
1.7
1.0
500
–1000
0.7
11
3.6
8
0.1
0.1
15
45
490
480
–1
–500
–500
–500
200
–300
–25
250
–250
±0.1
±0.05
±0.01
±0.05
±0.01
4
20
50
500
500
–0.2
800
–800
1.6
2.5
V
V
V
V
mA
mA
V/µs
kHz
MHz
µs
Output Sat Voltage High
l
2.3
1200
–500
Output Short-Circuit Current
Slew Rate
Full Power Bandwidth
Gain Bandwidth Product
Settling Time
Current Sense Characteristics
V
SENSE(MIN)
Minimum Current Sense Voltage
V
SENSE(4%)
Current Sense Voltage 4% of Full Scale
V
SENSE(10%)
Current Sense Voltage 10% of Full Scale
V
SENSE(FS)
I
BI
I
SENSE
–
I
FILTER
I
SENSE
+
Current Sense Voltage 100% of Full Scale
Current Limit Control Input Bias Current
SENSE
–
Input Current
FILTER Input Current
SENSE
+
Input Current
l
7
10
25
55
510
520
0.1
500
500
500
300
–200
25
mV
mV
mV
mV
mV
mV
µA
nA
nA
nA
nA
nA
nA
%
%
%
%
%
1970fe
VC
SRC
= VC
SNK
= 0.2V
VC
SRC
= VC
SNK
= 0.5V
VC
SRC
= VC
SNK
= 5V
l
l
l
VC
SRC
, VC
SNK
Pins
0V < (VC
SRC
, VC
SNK
) < 5V
0V < (VC
SRC
, VC
SNK
) < 5V
VC
SRC
= VC
SNK
= 0V
VC
SRC
= 5V, VC
SNK
= 0V
VC
SRC
= 0V, VC
SNK
= 5V
VC
SRC
= VC
SNK
= 5V
l
l
l
l
l
l
l
Current Sense Change with Output Voltage VC
SRC
= VC
SNK
= 5V, –12.5V < V
OUT
< 12.5V
Current Sense Change with Supply Voltage VC
SRC
= VC
SNK
= 5V, 6V < (V
CC
, V
+
) < 18V
2.5V < V
+
< 18V, V
CC
= 18V
–18V < (V
EE
, V
–
) < –2.5V
–18V < V
–
< –2.5V, V
EE
= –18V
For more information
www.linear.com/LT1970
3
LT1970
elecTrical characTerisTics
SYMBOL
R
CSF
PARAMETER
Current Sense Bandwidth
Resistance FILTER to SENSE
–
Logic Output Leakage
ISRC, ISNK, TSD
Logic Low Output Level
Logic Output Current Limit
V
ENABLE
I
ENABLE
I
SUPPLY
I
CC
I
CC(STBY)
t
ON
t
OFF
Enable Logic Threshold
Enable Pin Bias Current
Total Supply Current
V
CC
Supply Current
Supply Current Disabled
Turn-On Delay
Turn-Off Delay
V
CC
, V
+
and V
–
, V
EE
Connected
V
CC
, V
+
and V
–
, V
EE
Separate
V
CC
, V
+
and V
–
, V
EE
Connected, V
ENABLE
≤ 0.8V
(Note 7)
(Note 7)
l
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. See Test Circuit for standard test conditions.
CONDITIONS
MIN
750
TYP
2
1000
1250
1
0.2
25
0.8
–1
7
3
0.6
10
10
1.9
2.5
1
13
7
1.5
0.4
MAX
UNITS
MHz
Ω
µA
V
mA
V
µA
mA
mA
mA
µs
µs
Logic I/O Characteristics
V = 15V
I = 5mA (Note 6)
l
l
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device reli-
ability and lifetime.
Note 2:
The LT1970C is guaranteed functional over the operating tempera-
ture range of – 40°C and 85°C.
Note 3:
The LT1970C is guaranteed to meet specified performance from
0°C to 70°C. The LT1970C is designed, characterized and expected to
meet specified performance from –40°C to 85°C but is not tested or QA
sampled at these temperatures. The LT1970I is guaranteed to meet speci-
fied performance from –40°C to 85°C.
Note 4:
This parameter is not 100% tested.
Note 5:
Full power bandwidth is calculated from slew rate measurements:
FPBW = SR/(2 • π • V
P
)
Note 6:
The logic low output level of pin
TSD
is guaranteed by correlating
the output level of pin
ISRC
and pin
ISNK
over temperature.
Note 7:
Turn-on and turn-off delay are measured from V
ENABLE
crossing
1.6V to the OUT pin at 90% of normal output voltage.
Note 8:
Thermal resistance varies depending upon the amount of PC board
metal attached to the device. If the maximum dissipation of the package is
exceeded, the device will go into thermal shutdown and be protected.
Typical perForMance characTerisTics
Warm-Up Drift V
IO
vs Time
–100
V
OS
• 1000 (50mV/DIV)
–120
TOTAL SUPPLY CURRENT (mA)
INPUT BIAS CURRENT (nA)
–140
–160
–180
–200
–220
–240
–260
–15 –12 –9 –6 –3 0 3 6 9 12 15
COMMON MODE INPUT VOLTAGE (V)
1970 G02
Input Bias Current vs V
CM
V
S
= ±15V
Total Supply Current
vs Supply Voltage
14
12
10
8
6
4
2
0
–2
–4
–6
–8
–10
–12
–14
I
CC
+ I
V
+
125°C
25°C
–55°C
I
EE
+ I
V
–
–55°C
25°C
125°C
0
2
4
6
8 10 12 14
SUPPLY VOLTAGE (±V)
16
18
–I
BIAS
+I
BIAS
0V
TIME (100ms/DIV)
1970 G01
1970 G03
4
1970fe
For more information
www.linear.com/LT1970
LT1970
Typical perForMance characTerisTics
Supply Current vs Supply Voltage
4.5
4.0
SUPPLY CURRENT (mA)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
2
T
A
= 25°C
V
CC
= V
+
= –V
EE
= –V
–
4
6
8 10 12 14 16
SUPPLY VOLTAGE (±V)
18
20
I
VEE
I
VCC
I
V+
I
V –
OPEN-LOOP GAIN (dB)
70
60
50
40
30
20
10
0
–10
–20
–30
100
1k
10k 100k
1M
FREQUENCY (Hz)
10M
GAIN
PHASE
Open-Loop Gain and Phase
vs Frequency
100
90
80
PHASE MARGIN (DEG)
PHASE MARGIN (DEG)
70
60
50
40
30
20
10
0
100M
1970 G05
Phase Margin vs Supply Voltage
60
58
56
54
52
50
48
46
44
42
40
0
4
8 12 16 20 24 28 32
TOTAL SUPPLY VOLTAGE (V)
36
A
V
= –1
R
F
= R
G
= 1k
T
A
= 25°C
V
OUT
= V
S
/2
1870 G04
1970 G06
Gain Bandwidth vs Supply Voltage
5
4
VOLTAGE GAIN (dB)
A
V
= 100
10
Gain vs Frequency
A
V
= 1
10
Gain vs Frequency with C
LOAD
V
S
= ±15V
A
V
= 1
30nF
10nF
1nF
0
V
S
= ±15V
V
S
= ±5V
VOLTAGE GAIN (dB)
0
GAIN BANDWIDTH (MHz)
3
–10
–10
0nF
–20
2
1
0
–20
–30
–30
0
4
8 12 16 20 24 28 32
TOTAL SUPPLY VOLTAGE (V)
36
–40
10k
100k
1M
FREQUENCY (Hz)
10M
1970 G08
–40
10k
100k
1M
FREQUENCY (Hz)
10M
1970 G09
1970 G07
Output Impedance
100
V
S
= ±15V
600k
100k
OUTPUT IMPEDANCE ( )
A
V
= 100
1
A
V
= 10
0.1
A
V
= 1
OUTPUT IMPEDANCE (Ω)
10
10k
1k
100
10
Disabled Output Impedance
V
S
= ±15V
V
ENABLE
= 0.8V
1.8
1.7
1.6
SLEW RATE (V/µs)
1.5
1.4
1.3
1.2
1.1
10k
100k
1M
FREQUENCY (Hz)
10M
100M
1970 G11
Slew Rate vs Supply Voltage
FALLING
RISING
0.01
0.001
1k
10k
100k
1M
FREQUENCY (Hz)
10M
100M
1970 G10
1
1k
1.0
A
V
= –1
R
F
= R
G
= 1k
T
A
= 25°C
4
6
14
12
10
SUPPLY VOLTAGE (±V)
8
16
18
1970 G12
1970fe
For more information
www.linear.com/LT1970
5
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