TI TLV4120

TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
D
D
D
D
D
D
D
DGN PACKAGE
(TOP VIEW)
High Output Current Differential
Drive . . . >200 mA
Rail-To-Rail Output
Unity-Gain Bandwidth . . . 2.4 MHz
Slew Rate . . . 1.5 V/µs
Supply Current . . . 1.4 mA
Supply Voltage Range . . . 2.7 V to 5.5 V
Specified Temperature Range:
– TA = –40°C to 85°C . . . Industrial Grade
SHDN
VDD/2
IN+
IN–
1
8
2
7
3
6
4
5
VO –
GND
VDD
VO +
description
The TLV4120 single supply operational differential amplifier provides a differential output current in excess of
200 mA at 5 V. This enables the amplifier to be used as high current line drivers, buffers, or coil driver
applications. The TLV4120 has a shutdown feature that reduces the supply current down to 6 µA when the
amplifier is not active in the application.
The TLV4120 is available in the ultrasmall MSOP PowerPAD package, which offers the exceptional thermal
impedance required for amplifiers delivering high current levels.
AVAILABLE OPTIONS
TA
DEVICE
NUMBER OF
CHANNELS
PACKAGE TYPES
MSOP (DGN)†
SYMBOL
SHUTDOWN
– 40°C to 85°C
TLV4120
1
TLV4120IDGN
xxTIAHU
Yes
† This package is available taped and reeled. To order this packaging option, add an R suffix to the part number (e.g.,
TLV4120IDGNR).
functional block diagram
VDD 6
4
IN –
3
IN+
2
VDD/2
–
A1
+
VO+ 5
–
A2
+
VO– 8
7
GND
1
SHDN
Bias
Control
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PowerPAD is a trademark of Texas Instruments.
Copyright  2001, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
1
TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)†
Supply voltage, VDD (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 V
Differential input voltage, VID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± VDD
Input voltage range, VI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± VDD
Output current,IO (see Note 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800 mA
Continuous /RMS output current, IO (each output of amplifier): TJ ≤ 105°C . . . . . . . . . . . . . . . . . . . . 350 mA
TJ ≤ 150°C . . . . . . . . . . . . . . . . . . . . 110 mA
Peak output current, IO (each output of amplifier: TJ ≤ 105°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 mA
TJ ≤ 150°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 mA
Continuous total power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Dissipation Rating Table
Operating free-air temperature range, TA: I suffix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 40°C to 85°C
Maximum junction temperature, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150°C
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 65°C to 150°C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C
† Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTES: 1. All voltage values, except differential voltages, are with respect to GND.
2. To prevent permanent damage the die temperature must not exceed the maximum junction temperature.
DISSIPATION RATING TABLE
PACKAGE
θJC
(°C/W)
θJA
(°C/W)
TA ≤ 25°C
POWER RATING
TA = 85°C
POWER RATING
DGN (8)‡
4.7
52.7
2.37 W
1.23 W
‡ See The Texas Instruments document, PowerPAD Thermally Enhanced Package Application Report (literature number
SLMA002), for more information on the PowerPAD package. The thermal data was measured on a PCB layout based
on the information in the section entitled Texas Instruments Recommended Board for PowerPAD on page 33 of the before
mentioned document.
recommended operating conditions
Supply voltage, VDD
Common-mode input voltage range, VICR
Operating free-air temperature, TA
MIN
MAX
2.7
5.5
V
VDD–0.5
85
°C
0.5
I-suffix
–40
V(on)
Shutdown turnon/off voltage level§
<VDD/3
>VDD×0.75
V(off)
§ Relative to GND
2
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
UNIT
V
V
TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
electrical characteristics at recommend operating conditions, VDD = 2.7 V and 5 V (unless
otherwise noted)
dc performance
PARAMETER
VIO
CMRR
Input offset voltage
Common mode rejection ratio
Common-mode
TEST CONDITIONS
VIC = VDD/2
/2,
VDD = 2.7 V,,
RS = 50 Ω
VDD = 5 V,,
RS = 50 Ω
AVD
Large-signal
g
g
differential voltage
g
amplification
VDD = 2.7 V,
VO(PP)=1
1V
V,
VIC = VDD/2
VDD = 5 V,
VO(PP)=3
3V
V,
VIC = VDD/2
VO = VDD/2 ,
RS = 50 Ω
VIC = 0.5 to 2.2 V,,
VIC = 0.5 to 4.5 V,,
RL=100 Ω
TA†
25°C
MIN
TYP
MAX
100
3000
Full range
4000
25°C
69
Full range
66
25°C
71
Full range
68
25°C
80
Full range
70
25°C
90
Full range
80
UNITS
µV
95
dB
95
85
dB
RL=100 Ω
95
† Full range is – 40°C to 85°C for I suffix.
input characteristics
PARAMETER
IIO
Input offset current
IIB
Input bias current
ri(d)
Differential input resistance
CIC
Common-mode input capacitance
TEST CONDITIONS
VIC = VDD/2
/2
VO = VDD/2,
RS = 50 Ω
TA†
25°C
MIN
TYP
MAX
0.3
60
Full range
25°C
UNITS
300
0.3
Full range
60
pA
300
25°C
1000
GΩ
25°C
5
pF
VDD/2 biasing resistors
25°C
500
kΩ
Amplifier A2’s gain resistors
25°C
20
kΩ
f = 100 Hz
† Full range is – 40°C to 85°C for I suffix.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
3
TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
electrical characteristics at specified free-air temperature, VDD = 2.7 V and 5 V (unless
otherwise noted) (continued)
output characteristics
PARAMETER
TEST CONDITIONS
IOH = –10
10 mA
VDD = 2
2.7
7V
V, VIC = VDD/2
IOH =–100
= 100 mA
VOH
High level output voltage
High-level
10 mA
IOH = –10
VDD = 5 V
V, VIC = VDD/2
IOH = –100
100 mA
200 mA
IOH = –200
IOL = 10 mA
VDD = 2.7
2 7 V , VIC = VDD/2
IOL = 100 mA
VOL
Low level output voltage
Low–level
IOL = 10 mA
VDD = 5 V
V, VIC = VDD/2
IOL = 100 mA
IOL = 200 mA
IO
Output current
Measured at 0.5
0 5 V from rail
VDD = 2.7 V
VDD = 5 V
TA†
25°C
MIN
TYP
2.6
2.67
Full range
2.58
25°C
2.35
Full range
2.3
25°C
4.9
Full range
4.88
25°C
4.7
Full range
4.65
25°C
4.45
Full range
4.38
25°C
MAX
UNITS
2.4
4.96
V
4.8
4.55
0.03
Full range
0.1
0.12
25°C
0.3
Full range
0.4
0.5
25°C
0.03
Full range
0.1
0.12
25°C
0.2
Full range
V
0.3
0.35
25°C
0.5
Full range
0.55
0.62
320
25°C
mA
200
† Full range is– 40°C to 85°C for I suffix.
power supply
PARAMETER
IDD
PSRR
TEST CONDITIONS
Supply current
VO = VDD/2
/2, SHDN = <Vdd/3 V
Power supply rejection ratio (∆VDD / ∆VIO)
VDD =2.7 to 3.3 V,,
VIC = VDD/2 V, No load
VDD =2.7 to 5 V,
VIC = VDD/2 V, No load
† Full range is – 40°C to 85°C for I suffix.
4
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• DALLAS, TEXAS 75265
TA
25°C
MIN
TYP
MAX
1.4
1.7
Full range
2.3
25°C
80
Full range
75
25°C
70
Full range
65
UNITS
mA
94
84
dB
TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
electrical characteristics at specified free-air temperature, VDD = 2.7 V and 5 V (unless
otherwise noted) (continued)
dynamic performance
PARAMETER
GBWP
SR
φM
TA†
25°C
MIN
TYP
25°C
0.75
1.48
Full range
0.5
25°C
0.9
Full range
0.65
TEST CONDITIONS
RL=100 Ω
Gain bandwidth product
CL=10 pF
Vo(pp) = VDD/2,
RL = 100 Ω
Ω,
CL = 50 pF
F
Slew rate at unity gain
Phase margin
RL = 100 Ω
Ω,
Gain margin
Vn
Input noise voltage
† Full range is – 40°C to 85°C for I suffix.
VDD = 2
2.7
7V
VDD = 5 V
CL = 10 pF
UNITS
2.4
MHz
V/µs
1.57
60
25°C
f = 10 kHz
MAX
25°C
20
dB
10
nV/√Hz
shutdown characteristics
PARAMETER
IDD(SHDN)
TA†
25°C
TEST CONDITIONS
SHDN > Vdd × 0
0.75
75
Supply current in shutdown mode
Full range
MIN
TYP
MAX
6
12
50
UNITS
µA
† Full range is – 40°C to 85°C for I suffix.
TYPICAL CHARACTERISTICS
Table of Graphs
FIGURE
VOH
VOL
High-level output voltage
vs High-level output current
1, 3
Low-level output voltage
vs Low-level output current
2, 4
ZO
PO
Output impedance
vs Frequency
5
Output power
vs Load resistance
6
IDD
PSRR
Supply current
vs Supply voltage
7
Power supply rejection ratio
vs Frequency
8
Avd
Differential voltage amplification and phase
vs Frequency
9
Phase margin
vs Capacitive load
10
vs Free-air temperature
11
vs Supply voltage
12
Total harmonic distortion + noise
vs Frequency
13
Inverting large-signal pulse response
vs Time
14
Inverting small-signal pulse response
vs Time
15
Shutdown supply current
vs Free-air temperature
16
Shutdown supply current
vs Supply voltage
17
Shutdown mode pulse response
vs Time
18
Slew rate
IDD(SHDN)
IDD(SHDN)
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• DALLAS, TEXAS 75265
5
TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
TYPICAL CHARACTERISTICS
HIGH-LEVEL OUTPUT VOLTAGE
vs
HIGH-LEVEL OUTPUT CURRENT
LOW-LEVEL OUTPUT VOLTAGE
vs
LOW-LEVEL OUTPUT CURRENT
2.7
2.1
1.8
1.5
1.2
0.9
TA = 25°C
TA = 0°C
TA = –40°C
0.6
0.3
TA = 85°C
5.00
VO = Positive & Negative
VDD = 2.7 V
2.4
2.1
TA = 85°C
1.8
TA = 25°C
TA = 0°C
TA = –40°C
1.5
1.2
0.9
0.6
0.3
0
50 100 150 200 250 300 350 400 450
4.50
50
100
4.00
3.50
200
250
300
350
0
50 100 150 200 250 300 350 400 450 500
IOH – High-Level Output Current – mA
Figure 3
OUTPUT POWER
vs
LOAD RESISTANCE
800
1000
VO = Positive & Negative
VDD = 5 V
VDD = 2.7 V & 5 V
TA = 25° C
TA = 85°C
TA = 25°C
TA = 0°C
TA = –40°C
0.4
0.3
0.2
10
AV = –10
1
0.1
THD+N = 1%
f = 1 kHz
700
100
PO – Output Power – mW
Z o – Output Impedance – Ω
0.8
0.5
150
OUTPUT IMPEDANCE
vs
FREQUENCY
1.0
0.6
VO = Positive & Negative
VDD = 5 V
3.25
Figure 2
LOW-LEVEL OUTPUT VOLTAGE
vs
LOW-LEVEL OUTPUT CURRENT
0.7
TA = 25°C
TA = 0°C
TA = –40°C
3.75
IOL – Low-Level Output Current – mA
Figure 1
0.9
TA = 85°C
4.25
3
0
IOH – High-Level Output Current – mA
AV = –1
0.1
600
500
VDD = 5 V
400
300
VDD = 2.7 V
200
100
0
0
0.1
100
50 100 150 200 250 300 350 400 450 500
IOL – Low-Level Output Current – mA
Figure 4
1k
10k
100k
1M
f – Frequency – Hz
I DD – Supply Current – mA
TA = 25°C
1.2
TA = 0°C
1.0
TA = –40°C
0.8
0.6
VIC = Bypass voltage
1 µF Cap on bypass
AV= 1
RL = Open
0.2
0
0
0.5 1 1.5
16
48
56
24
32
40
RL – Load Resistance – Ω
Figure 6
2 2.5 3 3.5 4
4.5 5 5.5
PSRR – Power Supply Rejection Ratio – dB
TA = 85°C
0.4
8
POWER SUPPLY REJECTION RATIO
vs
FREQUENCY
1.6
1.4
0
10M
Figure 5
SUPPLY CURRENT
vs
SUPPLY VOLTAGE
80
70
60
50
40
30
20
VDD = 2.7 V & 5 V,
AV = –10,
RL = 100 Ω,
CL = 50 pF,
TA = 25°C
10
0
–10
–20
0.01
VDD – Supply Voltage – V
0.1
1
10
Figure 8
POST OFFICE BOX 655303
100
f – Frequency – Hz
Figure 7
6
4.75
0
0
VOL – Low-Level Output Voltage – V
V OH – High-Level Output Voltage – V
VO = Positive & Negative
VDD = 2.7 V
2.4
VOL – Low-Level Output Voltage – V
V OH – High-Level Output Voltage – V
2.7
HIGH-LEVEL OUTPUT VOLTAGE
vs
HIGH-LEVEL OUTPUT CURRENT
• DALLAS, TEXAS 75265
1k
10 k
64
TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
TYPICAL CHARACTERISTICS
PHASE MARGIN
vs
CAPACITIVE LOAD
80
180
80
70
150
70
60
120
50
90
40
60
30
30
10
0
–10
1k
0
VDD = 2.7 V & 5 V,
AV = Open Loop,
RL = 100 Ω,
CL = 10 pF,
TA = 25°C
10 k
Phase Margin – °
20
60
Phase – °
30
VDD = 2.7 V & 5 V,
RL = 100 Ω,
R null = 0,
TA = 25°C
10
–60
0
10
–90
10 M
1M
40
20
–30
100 k
50
100
SLEW RATE
vs
FREE-AIR TEMPERATURE
SLEW RATE
vs
SUPPLY VOLTAGE
2
1.75
1.75
SR+
1.50
SR – Slew Rate – V/µs
SR – Slew Rate – V/µs
SR+
SR–
1.25
1
0.75
VDD = 2.7 V & 5 V
AV = 1
RL= 100 Ω
CL = 50 pF
VO = 1 VPP
VI = 1.5 / 3 VPP
0.50
0.25
0
–40
1.50
SR–
1.25
1
0.75
AV = 1
RL =100 Ω
CL = 50 pF
VI = 1.5 VPP
0.50
0.25
0
–15
10
35
60
85
2.5
3
3.5
4
4.5
VDD – Supply Voltage – V
TA – Free-Air Temperature – °C
Figure 11
5
Figure 12
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
INVERTING LARGE-SIGNAL PULSE RESPONSE
vs
TIME
5
100
VI
VDD = 2.7 V & 5 V,
RL = 100 Ω,
CL = 50 pF
Both Channels
10
V O – Output Voltage – V
THD + N – Total Harmonic Distortion + Noise – dB
5k
Figure 10
Figure 9
2
1k
CL – Capacitive Load – pF
f – Frequency – Hz
AV = 10
1
AV = 1
0.1
0.01
10
100
1k
10 k
4
3
VDD = 5 V
RL =100 Ω
CL = 50 pF
AV = –1
TA = 25°C
5
2
1
0
V I – Input Voltage – V
A VD – Differential Voltage Amplification – dB
DIFFERENTIAL VOLTAGE AMPLIFICATION
AND PHASE
vs
FREQUENCY
4
VO+
3
2
VO–
1
0
0
100 k
2
4
6
8
10 12 14 16 18
t – Time – µs
f – Frequency – Hz
Figure 13
Figure 14
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• DALLAS, TEXAS 75265
7
TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
TYPICAL CHARACTERISTICS
INVERTING SMALL-SIGNAL PULSE RESPONSE
vs
TIME
VDD = 5 V
RL = 100 Ω
CL = 50 pF
AV = –1
TA = 25°C
0
–0.05
I DD(SD) – Shutdown Supply Current – µ A
–0.10
2.55
2.50
VO–
2.45
VO+
2.40
0
VIN = Bypass Voltage (VDD/2)
1 µF Cap on Bypass
AV = 1
RL = Open
Shutdown = VDD
3.5
3.0
2.5
2.0
1.5
1.0
VDD = 5 V
0.5
0.0
VDD = 2.7 V
–0.5
10 20 30 40 50 60 70 80 90
–1
–40
t – Time – µs
–15
10
35
60
TA – Free-Air Temperature – °C
Figure 15
Figure 16
SHUTDOWN SUPPLY CURRENT
vs
SUPPLY VOLTAGE
SHUTDOWN MODE PULSE RESPONSE
vs
TIME
0.9
0.8
0.7
0.6
SD in
V O – Output Voltage – V
I DD(SD) – Shutdown Supply Current – µ A
1.0
0.5
TA = 85°C
0.4
0.3
0.2
TA = 25°C
0.1
0.0
TA = –40°C
–0.1
0 0.5 1 1.5
2 2.5 3 3.5 4 4.5 5
3
1
0
VO+ and VO–
–1
5.5
0
Figure 17
POST OFFICE BOX 655303
VDD = 5 V
RL = 100 Ω
CL = 10 pF
AV = 1
VI = VDD/2
TA = 25°C
2
VDD – Supply Voltage – V
8
85
200
400 600 800 1000 1200
t – Time – µs
Figure 18
• DALLAS, TEXAS 75265
6
4
2
0
SD – Shutdown Pulse – V
V O – Output Voltage – V
0.05
4.0
V I – Input Voltage – V
0.10
VI
SHUTDOWN SUPPLY CURRENT
vs
FREE-AIR TEMPERATURE
TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
APPLICATION INFORMATION
differential output drive
The TLV4120 is two amplifiers arranged to produce high output current differential drive. The first amplifier, A1,
is an operational amplifier, with both inputs uncommitted. This enables the first amplifier to be configured as an
inverting amplifier, a noninverting amplifier, or even a difference amplifier. The second amplifier, A2, is internally
configured as an inverting amplifier and biased about VDD/2.
VDD 6
VDD
VDD/2
4
IN –
3
IN+
2
VDD/2
VO+ 5
–
A1
+
RL
–
A2
VO– 8
+
7
GND
1
SHDN
Bias
Control
Figure 19
This approach makes a simple solution to single-ended to differential drive or even differential to differential
drive.
When using the TLV4120 to drive heavy differential loads, care must be taken not to saturate the output of the
first amplifier, as the second amplifier will produce a mirror image (about VDD/2) of the first amplifier’s output.
This can lead to asymmetrical differential output swings.
This differential output drive configuration is ideal for low frequency high current drive applications, such as line
drivers, driving LVDTs.
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• DALLAS, TEXAS 75265
9
TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
APPLICATION INFORMATION
Figure 20 shows the TLV4120 amplifier driving both ends of the load. There are several potential benefits to
this differential drive configuration but initially consider power to the load. The differential drive to the load means
that as one side is slewing up, the other side is slewing down, and vice versa. This doubles the voltage swing
on the load as compared to a ground-referenced load, quadrupling the power delivered to the load.
VDD
VO(PP)
2x VO(PP)
VDD
–VO(PP)
–1
Figure 20. Bridge-Tied Load Configuration
component selection
RF
VDD 6
VDD/2
CS
VIN
RS
4
IN –
CPS
VO+ 5
–
A1
3
IN+
2
VDD/2
+
RL
CB
–
A2
VO– 8
+
7
GND
1 = Off
0 = On
1
SHDN
Bias
Control
Figure 21. Driving a Capacitive Load
10
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• DALLAS, TEXAS 75265
VO
TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
APPLICATION INFORMATION
gain setting resistors, RF and RS
ǒǓ
ǒ Ǔ
The differential gain for the TLV4120, with A1 configured as an inverter, is set by resistors RF and RS using the
following equation:
DiffGain
+ –2
R
R
F
S
The differential gain for the TLV4120, with A1 in a noninverting configuration, is set by resistors RF and RS using
the following equation:
DiffGain
+2
1
) RRF
S
Differential drive operation brings about the factor 2 in the gain equation due to amplifier A2, configured as an
inverter, mirroring the voltage swing across the load.
Given that the TLV4120 is a MOS amplifier, the input impedance is very high; consequently input bias currents
in most cases will not generally be a concern (see offset voltage application section). However, the noise in the
circuit will increase as RF increases. Typical values for RF will range between 5 kΩ and 20 kΩ.
Large values of feedback resistor, RF, at low gains can cause instability due to the pole caused by the input
capacitance. This can be alleviated by either reducing the size of RF or by putting a small capacitor in parallel
with RF.
AC coupling capacitor, CS
When the input to the TLV4120 will be ac coupled to the input source, a high pass filter is formed with a corner
frequency equal to:
fc
+ 2pR1 C
S S
The value of CS is important to consider as it directly affects the low frequency operation of the circuit.
A further consideration for this capacitor is the leakage path from the input source through the input network
(RS, CS) and the feedback resistor (RF ) to the load. This leakage current creates a dc-offset voltage at the input
to the amplifier that reduces useful headroom, especially in high gain applications. For this reason, a
low-leakage tantalum or ceramic capacitor is the best choice. When polarized capacitors are used, the positive
side of the capacitor should face the amplifier input in most applications, as the dc level there is held at VDD/2,
which is likely higher than the source dc level. It is important to confirm the capacitor polarity in the application.
power supply decoupling, CPS
The TLV4120 is a high-performance CMOS amplifier that requires adequate power supply decoupling to ensure
stability and low total harmonic distortion (THD). Optimum decoupling is achieved by using two capacitors of
different types that target different types of noise on the power supply leads. For higher frequency transients,
spikes, or digital hash on the line, a good low equivalent-series-resistance (ESR) ceramic capacitor, typically
0.1 µF placed as close as possible to the device VDD lead works best. For filtering lower-frequency noise signals,
a larger aluminum electrolytic capacitor of 10 µF or greater placed near the amplifier is recommended.
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TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
APPLICATION INFORMATION
VDD/2 bypass capacitor, CB
The VDD/2 bypass capacitor, CB, is the most critical capacitor and serves several important functions. During
start-up or recovery from shutdown mode, CB determines the rate at which the amplifier starts up. The second
function is to reduce noise produced by the power supply caused by coupling into the output drive signal. This
noise is from the mid-rail generation circuit internal to the amplifier, which appears as degraded PSRR and THD
+ N. The capacitor is fed from two internal 500-kΩ potential-dividing resistors. To keep the start-up bounce as
low as possible, the relationship shown in equation 4 should be maintained. This ensures the input capacitor
is fully charged before the bypass capacitor is fully charged and the amplifier starts up.
ǒ
10
C
B
v
WǓ ǒ
250 k
1
R
F
Ǔ
) RS
C
S
As an example, consider a circuit where CB is 2.2 µF, CS is 0.47 µF, RF is 50 kΩ, and RS is 10 kΩ. Inserting these
values into equation 4 produces the following:
18.2 ≤ 35.5
which satisfies the rule. For bypass capacitor, CB , 0.1-µF to 2.2-µF ceramic or tantalum low-ESR capacitors
are recommended for the best stability and noise performance.
using low-ESR capacitors
Low-ESR capacitors are recommended. A real (as opposed to ideal) capacitor can be modeled simply as a
resistor in series with an ideal capacitor. The voltage drop across this resistor minimizes the beneficial effects
of the capacitor in the circuit. The lower the equivalent value of this resistance, the more the real capacitor
behaves like an ideal capacitor.
shutdown function
The TLV4120 has a shutdown terminal for conserving power in energy sensitive applications. When the
shutdown terminal is pulled high the amplifier is disabled, placing the outputs into a high impedance state and
reducing the supply current to the order of microamperes.
To enable the amplifier, the shutdown terminal must be pulled low. If open drain logic is used, pull-up resistors
must be employed to ensure proper and known shutdown status. It is not recommended that the shutdown input
is left to float, as the device could inadvertently shutdown.
12
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TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
APPLICATION INFORMATION
driving a capacitive load
When the amplifier is used to drive heavy capacitive loads, the device’s phase margin will be reduced which
could lead to high frequency ringing or oscillations. The TLV4120’s high current drive capability reduces this
possibility. However, for capacitive loads of greater than 1 nF, it is suggested that a resistor be placed in series
(RNULL ) with the output of the amplifier as shown in Figure 22 which should help reduce the ringing.
RF
CS
RS
–
A1
SHDN
+
RNULL
CL
RL
CB
–
RNULL
A2
+
VDD/2
CL
NOTE: RNULL will reduce the output drive capability of the TLV4120.
Figure 22. Driving a Capacitive Load
offset voltage
The output offset voltage, (VOO) is the sum of:
1. The input offset voltage (VIO) multiplied by the noninverting gain
2. The noninverting input bias current (IIB) multiplied by the resistance on this node multiplied by the
noninverting gain
3. The inverting bias current multiplied by the feedback resistor.
RF
IIB–
RG
–
VI
RBIAS/2
+
VO
IIB+
Figure 23. Output Offset Voltage Model
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TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
APPLICATION INFORMATION
offset voltage (continued)
The differential nature of the TLV4120 means that both amplifiers must be considered together to calculate the
differential output offset voltage (VDOO) (see Figure 24). The VOO of amplifier A1 will be inverted by amplifier
A2. This doubles A1’s VOO and has A2’s VOO added to it, yielding:
V
DOO
+ 2VIO1
ǒ ǒ ǓǓ
1
)
R
R
F
S
ǒ ǒ ǓǓ
" IIB) 500k
1
)
R
R
F
S
" 2IIB– RF–2VIO2 " IIB) 500k " IIB–20k
RF
IIB–
RS
VIO
–
A1
+
20 kΩ
IIB+
VDD
20 kΩ
IIB–
500 kΩ
VIO
–
A2
+
500 kΩ
IIB+
Figure 24. TLV4120 Offset Voltage Model
14
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TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
APPLICATION INFORMATION
general power design considerations
When driving heavy loads at high junction temperatures there is an increased probability of electromigration
affecting the long term reliability of ICs. Therefore for this not to be an issue:
D
D
The output current must be limited (at these high junction temperatures) or
The junction temperature must be limited.
The maximum continuous output current at a die temperature of 150°C will be 1/3 of the current at 105°C.
The junction temperature will be dependent on the ambient temperature around the IC, thermal impedance from
the die to the ambient, and power dissipated within the IC.
TJ = TA + θJA × PDIS
Where:
PDIS is the IC power dissipation and is equal to the output current multiplied by the voltage dropped across
the output of the IC.
θJA is the thermal impedance between the junction and the ambient temperature of the IC.
TJ is the junction temperature.
TA is the ambient temperature.
Reducing one or more of these factors will result in a reduced die temperature.
The use of the MSOP PowerPAD dramatically reduces the thermal impedance from junction to case. And with
correct mounting, the reduced thermal impedance will greatly increase the IC’s permissible power dissipation
and output current handling capability. For example, the power dissipation of the PowerPAD is increased to
above 1 W. Sinusoidal and pulse-width modulated output signals will also increase the output current capability.
The equivalent dc current is proportional to the square-root of the duty cycle:
I
DC(EQ)
+ ICont
Ǹ(duty cycle)
CURRENT DUTY CYCLE
AT PEAK RATED CURRENT
EQUIVALENT DC CURRENT
AS A PERCENTAGE OF PEAK
CURRENT
100
100
70
84
50
71
Note that with an operational amplifier, a duty cycle of 70% will often result in the op-amp sourcing current 70%
of the time and sinking current 30%; therefore, the equivalent dc current will still be 0.84 times the continuous
current rating at a particular junction temperature.
The differential nature of the TLV4120 means that it will dissipate approximately four times the power of a
single-ended amplifier driving a similar load referenced to mid rail. The TLV4120 will however be delivering four
times the power to the load.
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TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
APPLICATION INFORMATION
general PowerPAD design considerations
The TLV4120 is available in a thermally-enhanced PowerPAD package. This package is constructed using a
downset leadframe upon which the die is mounted [see Figure 25(a) and Figure 25(b)]. This arrangement results
in the lead frame being exposed as a thermal pad on the underside of the package [see Figure 25(c)]. Because
this thermal pad has direct thermal contact with the die, excellent thermal performance can be achieved by
providing a good thermal path away from the thermal pad.
The PowerPAD package allows for both assembly and thermal management in one manufacturing operation.
During the surface-mount solder operation (when the leads are being soldered), the thermal pad can also be
soldered to a copper area underneath the package. Through the use of thermal paths within this copper area,
heat can be conducted away from the package into either a ground plane or other heat dissipating device.
The PowerPAD package represents a breakthrough in combining the small area and ease of assembly of
surface mount with the, heretofore, awkward mechanical methods of heatsinking.
DIE
Side View (a)
Thermal
Pad
DIE
End View (b)
Bottom View (c)
NOTE A: The thermal pad is electrically isolated from all terminals in the package.
Figure 25. Views of Thermally Enhanced DGN Package
Although there are many ways to properly heatsink the PowerPAD package, the following steps illustrate the
recommended approach.
Thermal Pad Area
Single or Dual
68 mils x 70 mils) with 5 vias
(Via diameter = 13 mils
Figure 26. PowerPAD PCB Etch and Via Pattern
16
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TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
APPLICATION INFORMATION
general PowerPAD design considerations (continued)
1. Prepare the PCB with a top side etch pattern as shown in Figure 26. There should be etch for the leads as
well as etch for the thermal pad.
2. Place five holes (dual) or nine holes (quad) in the area of the thermal pad. These holes should be 13 mils
in diameter. Keep them small so that solder wicking through the holes is not a problem during reflow.
3. Additional vias may be placed anywhere along the thermal plane outside of the thermal pad area. This helps
dissipate the heat generated by the TLV4120 IC. These additional vias may be larger than the 13-mil
diameter vias directly under the thermal pad. They can be larger because they are not in the thermal pad
area to be soldered so that wicking is not a problem.
4. Connect all holes to the internal ground plane.
5. When connecting these holes to the ground plane, do not use the typical web or spoke via connection
methodology. Web connections have a high thermal resistance connection that is useful for slowing the heat
transfer during soldering operations. This makes the soldering of vias that have plane connections easier.
In this application, however, low thermal resistance is desired for the most efficient heat transfer. Therefore,
the holes under the TLV4120 PowerPAD package should make their connection to the internal ground plane
with a complete connection around the entire circumference of the plated-through hole.
6. The top-side solder mask should leave the terminals of the package and the thermal pad area with its five
holes (dual) or nine holes (quad) exposed. The bottom-side solder mask should cover the five or nine holes
of the thermal pad area. This prevents solder from being pulled away from the thermal pad area during the
reflow process.
7. Apply solder paste to the exposed thermal pad area and all of the IC terminals.
8. With these preparatory steps in place, the TLV4120 IC is simply placed in position and run through the solder
reflow operation as any standard surface-mount component. This results in a part that is properly installed.
For a given θJA, the maximum power dissipation is shown in Figure 27 and is calculated by the following formula:
P
Where:
+
D
ǒ Ǔ
T
–T
MAX A
q JA
PD = Maximum power dissipation of TLV4120 IC (watts)
TMAX = Absolute maximum junction temperature (150°C)
TA
= Free-ambient air temperature (°C)
θJA = θJC + θCA
θJC = Thermal coefficient from junction to case
θCA = Thermal coefficient from case to ambient air (°C/W)
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TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
APPLICATION INFORMATION
general PowerPAD design considerations (continued)
MAXIMUM POWER DISSIPATION
vs
FREE-AIR TEMPERATURE
4
TJ = 150°C
Maximum Power Dissipation – W
3.5
3
2.5
2
DGN Package
Low-K Test PCB
θJA = 52.7°C/W
1.0
1
0.5
0
–55 –40 –25 –10 5 20 35 50 65 80 95 110 125
TA – Free-Air Temperature – °C
NOTE A: Results are with no air flow and using JEDEC Standard Low-K test PCB.
Figure 27. Maximum Power Dissipation vs Free-Air Temperature
The next consideration is the package constraints. The two sources of heat within an amplifier are quiescent
power and output power. The designer should never forget about the quiescent heat generated within the
device, especially multi-amplifier devices. Because these devices have linear output stages (Class A-B), most
of the heat dissipation is at low output voltages with high output currents.
The other key factor when dealing with power dissipation is how the devices are mounted on the PCB. The
PowerPAD devices are extremely useful for heat dissipation. But, the device should always be soldered to a
copper plane to fully use the heat dissipation properties of the PowerPAD. The SOIC package, on the other
hand, is highly dependent on how it is mounted on the PCB. As more trace and copper area is placed around
the device, θJA decreases and the heat dissipation capability increases. The currents and voltages shown in
these graphs are for the total package. For the dual or quad amplifier packages, the sum of the RMS output
currents and voltages should be used to choose the proper package.
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TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310A – DECEMBER 2000 – REVISED MARCH 2001
MECHANICAL INFORMATION
DGN (S-PDSO-G8)
PowerPAD PLASTIC SMALL-OUTLINE PACKAGE
0,38
0,25
0,65
8
0,25 M
5
Thermal Pad
(See Note D)
0,15 NOM
3,05
2,95
4,98
4,78
Gage Plane
0,25
1
0°– 6°
4
3,05
2,95
0,69
0,41
Seating Plane
1,07 MAX
0,15
0,05
0,10
4073271/A 04/98
NOTES: A.
B.
C.
D.
All linear dimensions are in millimeters.
This drawing is subject to change without notice.
Body dimensions include mold flash or protrusions.
The package thermal performance may be enhanced by attaching an external heat sink to the thermal pad.
This pad is electrically and thermally connected to the backside of the die and possibly selected leads.
E. Falls within JEDEC MO-187
PowerPAD is a trademark of Texas Instruments.
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