ADA4870_技术文档

High Speed, High Voltage,

1 A Output Drive Amplifier

ADA4870

Data Sheet

FEATURES

FUNCTIONAL BLOCK DIAGRAM

Ideal for driving high capacitive or low resistive loads

Wide supply range: 10 V to 40 V

High output current drive: 1 A

Wide output voltage swing: 37 V swing with 40 V supply

High slew rate: 2500 V/µs

High bandwidth: 52 MHz large signal, 70 MHz small signal

Low noise: 2.1 nV/√Hz

Quiescent current: 32.5 mA

1

2

20

19

18

17

16

15

14

13

12

11

V

CC

V

TFL

SD

ADA4870

CC

3

V

4

OUT

ON

5

NC

6

INP

INN

OUT

NC

7

Power down: 0.75 mA

Short-circuit protection and flag

Current limit: 1.2 A

8

V

EE

9

V

EE

10

V

EE

Thermal protection

Figure 1.

APPLICATIONS

Envelope tracking

Power FET driver

Ultrasound

Piezo drivers

PIN diode drivers

Waveform generation

Automated test equipment (ATE)

CCD panel drivers

Composite amplifiers

GENERAL DESCRIPTION

The ADA4870 is a unity gain stable, high speed current

feedback amplifier capable of delivering 1 A of output current

and 2500 V/μs slew rate from a 40 V supply. Manufactured

using the Analog Devices, Inc., proprietary high voltage extra

fast complementary bipolar (XFCB) process, the innovative

architecture of the ADA4870 enables high output power, high

speed signal processing solutions in applications that require

driving a low impedance load.

20

15

10

5

4,000

3,000

2,000

1,000

0

V

OUT

SLEW RATE

0

The ADA4870 is ideal for driving high voltage power FETs,

piezo transducers, PIN diodes, CCD panels, and a variety of

other demanding applications that require high speed from

high supply voltage at high output current.

–5

–10

–15

–20

–1,000

–2,000

–3,000

–4,000

The ADA4870 is available in a power SOIC package (PSOP_3),

featuring an exposed thermal slug that provides high thermal

conductivity, enabling efficient heat transfer for improved perfor-

mance and reliability in demanding applications. The ADA4870

operates over the industrial temperature range (−40°C to +85°C).

TIME (45ns/DIV)

Figure 2. Slew Rate, V_S= 20 V, V_OUT= 30 V p-p, A_V= +2,

R_F= 1.5 kΩ, C_L= 300 pF, R_S= 5 Ω

Rev. 0

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Tel: 781.329.4700

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ADA4870* Product Page Quick Links

Last Content Update: 11/01/2016

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• ADA4870 Evaluation Board

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• ADA4870 Material Declaration

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• Quality And Reliability

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Documentation

Data Sheet

• ADA4870-KGD: Known Good Die Data Sheet

• ADA4870: High Speed, High Voltage, 1A Output Drive

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• UG-685: Evaluating the ADA4870 High Speed, High

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ADA4870

Data Sheet

TABLE OF CONTENTS

Features .............................................................................................. 1

SD

Shutdown ( ) ........................................................................... 19

Feedback Resistor Selection...................................................... 19

Capacitive Load Driving ........................................................... 19

Heat and Thermal Management .............................................. 20

Power Dissipation....................................................................... 20

Safe Operating Area................................................................... 21

Printed Circuit Board (PCB) .................................................... 22

Thermal Modeling ..................................................................... 22

Heat Sink Selection .................................................................... 22

Power Supplies and Decoupling............................................... 22

Composite Amplifier ................................................................. 23

Outline Dimensions....................................................................... 24

Ordering Guide .......................................................................... 24

Applications....................................................................................... 1

Functional Block Diagram .............................................................. 1

General Description......................................................................... 1

Revision History ............................................................................... 2

Specifications..................................................................................... 3

20 V Supply................................................................................. 3

5 V Supply................................................................................... 4

Absolute Maximum Ratings............................................................ 6

Maximum Power Dissipation ..................................................... 6

ESD Caution.................................................................................. 6

Pin Configuration and Function Descriptions............................. 7

Typical Performance Characteristics ............................................. 8

Applications Information .............................................................. 19

ON

, Initial Power-Up, and Short-Circuit................................ 19

Thermal Protection.................................................................... 19

REVISION HISTORY

5/14—Revision 0: Initial Version

Rev. 0 | Page 2 of 24

Data Sheet

ADA4870

SPECIFICATIONS

20 V SUPPLY

T_CASE= 25°C, A_V= −5, R_F= 1.21 kΩ, R_G= 243 Ω, C_L= 300 pF, R_S= 5 Ω, unless otherwise noted.

Table 1.

Parameter

Test Conditions/Comments

Min

Typ

Max

Unit

DYNAMIC PERFORMANCE

−3 dB Bandwidth

V_OUT= 2 V p-p

V_OUT= 2 V p-p, A_V= +2

V_OUT= 20 V p-p

V_OUT= 30 V step, A_V= +2

V_OUT= 10 V step

60

70

52

2500

82

MHz

V/µs

ns

Slew Rate (Peak)

Settling Time to 0.1%

NOISE/DISTORTION PERFORMANCE

Harmonic Distortion, HD2/HD3

f = 30 MHz, V_OUT= 20 V p-p, A_V= −10

f = 1 MHz, V_OUT= 20 V p-p, A_V= −10

f = 0.1 MHz, V_OUT= 20 V p-p, A_V= −10

f = 1 MHz, V_OUT= 20 V p-p, R_L= 25 Ω, A_V= −10

f = 0.1 MHz, V_OUT= 20 V p-p, R_L= 25 Ω, A_V= −10

f = 100 kHz

−40/−39

−91/−74

−95/−96

−70/−77

−79/−99

2.1

dBc

nV/√Hz

Input Voltage Noise Density

Input Current Noise Density

INP

f = 100 kHz

4.2

47

pA/√Hz

INN

DC PERFORMANCE

Input Offset Voltage

Input Offset Voltage Drift

Input Bias Current

−15

−1

4

+10

mV

µV/°C

Noninverting Input

Inverting Input

Input Bias Current Drift, Inverting Input

Open-Loop Transresistance

INPUT CHARACTERISTICS

Input Resistance

9

23

−25

µA

nA/°C

MΩ

−12

24

2.5

INP

2

MΩ

pF

V

Input Capacitance

0.75

18

60

Input Common-Mode Voltage Range (V_ICM

Common-Mode Rejection Ratio

SD PIN (SHUTDOWN)

)

V_ICM= 2 V, 18 V

58

dB

Input Voltages

High (enabled)

V_EE+ 1.1

V_EE

V_EE+ 5

V_EE+ 0.9

V

µA

Low (power-down)

Enabled (SD = V_EE+ 5 V)

Power down SD = V_EE)

Input Bias Current

110

−50

ON PIN (RESET AND SHORT-CIRCUIT

PROTECTION)

Input Voltages

High (power-down)

Low (enabled)

V_EE+ 1.8

V_EE

V_EE+ 5

V_EE+ 1.3

V

Input Bias Current

Enabled (ON = V_EE)

Power down (ON = V_EE+ 5 V)

−75

100

µA

OUTPUT CHARACTERISTICS

Output Voltage Range

R_G= 1.2 kΩ, R_L= open

R_G= 1.2 kΩ, R_L= 50 Ω

18.6

18

V

A

Output Current Drive

Short-Circuit Protection Current Limit

1

ON = floating

1.2

Rev. 0 | Page 3 of 24

ADA4870

Data Sheet

Parameter

Test Conditions/Comments

Min

Typ

Max

Unit

POWER SUPPLY

Operating Range

Quiescent Current

10

40

33

1

V

SD = V_EE+ 5 V, ON = V_EE

32.5

0.75

5.1

69

mA

dB

SD = V_EE, ON = not applicable

SD = V_EE+ 5 V, ON = V_EE+ 5 V

5.8

Positive Power Supply Rejection Ratio

Negative Power Supply Rejection Ratio

67

62

64

5 V SUPPLY

T_CASE= 25°C, A_V= −5, R_F= 1.21 kΩ, R_G= 243 Ω, C_L= 300 pF, R_S= 5 Ω, unless otherwise noted.

Table 2.

Parameter

Test Conditions/Comments

Min

Typ

Max

Unit

DYNAMIC PERFORMANCE

−3 dB Bandwidth

Settling Time to 0.1%

V_OUT= 2 V p-p

V_OUT= 2 V step

52

55

MHz

ns

NOISE/DISTORTION PERFORMANCE

Harmonic Distortion, HD2/HD3

f = 30 MHz, V_OUT= 2 V p-p, A_V= −10

f = 1 MHz, V_OUT= 2 V p-p, A_V= −10

f = 0.1 MHz, V_OUT= 2 V p-p, A_V= −10

f = 1 MHz, V_OUT= 2 V p-p, R_L= 25 Ω, A_V= −10

f = 0.1 MHz, V_OUT= 2 V p-p, R_L= 25 Ω, A_V= −10

f = 100 kHz

−42/−38

−90/−88

−101/−107

−70/−66

−85/−86

2.1

dBc

nV/√Hz

Input Voltage Noise Density

Input Current Noise Density

INP

f = 100 kHz

4.2

47

pA/√Hz

INN

DC PERFORMANCE

Input Offset Voltage

Input Offset Voltage Drift

Input Bias Current

−15

−4

14

+5

mV

µV/°C

Noninverting Input

Inverting Input

Input Bias Current Drift, Inverting Input

Open-Loop Transresistance

INPUT CHARACTERISTICS

Input Resistance

13

−5

10

1.9

23

−18

µA

nA/°C

MΩ

INP

2

MΩ

pF

V

Input Capacitance

0.75

3.0

59

Input Common-Mode Voltage Range (V_ICM

Common-Mode Rejection Ratio

SD PIN (SHUTDOWN)

)

V_ICM= 0.5 V, 3.0 V

57

dB

Input Voltages

High (enabled)

V_EE+ 1.1

V_EE

V_EE+ 5

V_EE+ 0.9

V

µA

Low (power-down)

Enabled (SD = V_EE+ 5 V)

Power down (SD = V_EE)

Input Bias Current

110

−65

ON PIN (RESET AND SHORT-CIRCUIT

PROTECTION)

Input Voltages

High (power-down)

Low (enabled)

V_EE+ 1.8

V_EE

V_EE+ 5

V_EE+ 1.3

V

Input Bias Current

Enabled (ON = V_EE)

Power down (ON = V_EE+ 5 V)

−75

100

µA

Rev. 0 | Page 4 of 24

Data Sheet

ADA4870

Parameter

Test Conditions/Comments

R_G= 1.2 kΩ, R_L= open

ON = floating

Min

Typ

Max

Unit

OUTPUT CHARACTERISTICS

Output Voltage Range

Output Current Drive

3.7

1

1.2

V

A

Short-Circuit Protection Current Limit

POWER SUPPLY

Operating Range

Quiescent Current

10

40

30

1

V

SD = V_EE+ 5 V, ON = V_EE

28

mA

dB

SD = V_EE, ON = not applicable

SD = V_EE+ 5 V, ON = V_EE+ 5 V

0.65

4.7

68

5.5

Positive Power Supply Rejection Ratio

Negative Power Supply Rejection Ratio

66

61

63

Rev. 0 | Page 5 of 24

ADA4870

Data Sheet

ABSOLUTE MAXIMUM RATINGS

Table 3.

MAXIMUM POWER DISSIPATION

The maximum safe power dissipation in the package is limited by

the associated rise in junction temperature (T_J) on the die. At

approximately 150°C, which is the glass transition temperature,

the plastic changes its properties. Exceeding a junction temperature

of 150°C can result in changes in the silicon devices, potentially

causing failure. Table 4 shows the junction to case thermal

resistance (θ_JC) for the PSOP_3 package. For more detailed

information on power dissipation and thermal management,

see the Applications Information section.

Parameter

Rating

Supply Voltage

Power Dissipation

42 V

See the Power Dissipation

section and the Safe

Operating Area section

Common-Mode Input Voltage Range V_EEto V_CC

Differential Input Voltage Range

Storage Temperature Range

Operating Temperature Range

Lead Temperature (Soldering, 10 sec)

Junction Temperature

0.7 V

−65°C to +150°C

−40°C to +85°C

300°C

Table 4. Thermal Resistance

150°C

Package Type

θ_JC

Unit

Stresses at or above those listed under Absolute Maximum

Ratings may cause permanent damage to the product. This is a

stress rating only; functional operation of the product at these

or any other conditions above those indicated in the operational

section of this specification is not implied. Operation beyond

the maximum operating conditions for extended periods may

affect product reliability.

20-Lead PSOP_3

1.1

°C/W

ESD CAUTION

Rev. 0 | Page 6 of 24

Data Sheet

ADA4870

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

1

2

20

19

18

17

16

15

14

13

12

11

V

CC

V

TFL

SD

CC

3

V

4

OUT

ON

NC

ADA4870

TOP VIEW

(Not to Scale)

5

6

INP

INN

OUT

NC

7

8

V

EE

9

V

EE

10

V

EE

NOTES

1. NC = NO CONNECT. DO NOT CONNECT TO THIS PIN.

2. CONNECT THE EXPOSED PAD TO A SOLID EXTERNAL

PLANE WITH LOW THERMAL RESISTANCE.

Figure 3. Pin Configuration

Table 5. Pin Function Descriptions

Pin No.

Mnemonic Description

1

V_CC

Positive Power Supply Input.

2

3

TFL

SD

Thermal Monitor and Short-Circuit Flag (Referenced to V_EE).

Shutdown (Active Low, Referenced to V_EE).

Turn On/Enable (Active Low, Referenced to V_EE).

No Connect. Do not connect to this pin.

Noninverting Input.

4

ON

NC

INP

INN

OUT

NC

V_EE

OUT

V_CC

5

6

7

8

Inverting Input.

Output Connection for Feedback Resistor.

No Connect. Do not connect to this pin.

Negative Power Supply Input.

Output.

Positive Power Supply Input.

9

10 to 13

14 to 17

18 to 20

EPAD

Exposed Thermal Pad. No internal electrical connection. Connect the exposed pad to a solid external plane

with low thermal resistance.

Rev. 0 | Page 7 of 24

ADA4870

Data Sheet

TYPICAL PERFORMANCE CHARACTERISTICS

T_CASE= 25°C, unless otherwise noted.

12

9

12

–20°C

+25°C

+100°C

+25°C

9

6

+100°C

6

3

0

–3

–6

–9

–12

–15

–18

–3

–6

–9

V

R

A

C

R

= ±20V

V

R

A

C

R

= ±5V

S

= 20V p-p

= 2V p-p

OUT

–12

–15

–18

OUT

= 1.21kΩ

F

V

L

S

F

V

L

S

= −2

= 300pF

= 5Ω

= 300pF

= 5Ω

1

10

100

1000

1

10

100

1000

FREQUENCY (MHz)

Figure 4. Small Signal Frequency Response vs. Case Temperature, A_V= −2,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 7. Large Signal Frequency Response vs. Case Temperature, A_V= −2,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

21

–20°C

+25°C

18

15

18

+100°C

15

12

9

12

9

6

3

0

V

R

A

C

R

= ±5V

V

R

A

C

R

= ±20V

S

= 2V p-p

= 20V p-p

OUT

–3

–6

–9

OUT

–3

–6

–9

= 1.21kΩ

F

V

L

S

F

V

L

S

= −5

= 300pF

= 5Ω

= 300pF

= 5Ω

1

10

100

1000

1

10

100

1000

FREQUENCY (MHz)

Figure 5. Small Signal Frequency Response vs. Case Temperature, A_V= −5,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 8. Large Signal Frequency Response vs. Case Temperature, A_V= −5,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

27

–20°C

+25°C

+100°C

–20°C

+25°C

24

+100°C

21

18

15

12

9

21

18

15

12

9

6

V

R

A

C

R

= ±20V

OUT

= 1.21kΩ

= −10

= 300pF

= 5Ω

V

R

A

C

R

= ±5V

OUT

= 1.21kΩ

= −10

= 300pF

= 5Ω

S

= 20V p-p

= 2V p-p

3

0

3

0

F

V

L

S

F

V

L

S

–3

1

10

100

1000

1

10

100

1000

FREQUENCY (MHz)

Figure 6. Small Signal Frequency Response vs. Case Temperature, A_V= −10,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 9. Large Signal Frequency Response vs. Case Temperature, A_V= −10,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Rev. 0 | Page 8 of 24

Data Sheet

ADA4870

12

9

12

9

–20°C

+25°C

+100°C

–20°C

+25°C

+100°C

6

3

0

–3

–6

–9

–12

–15

–18

–3

–6

–9

V

R

A

C

R

= ±20V

S

V

R

A

C

R

= ±5V

S

= 20V p-p

OUT

= 2V p-p

–12

–15

–18

OUT

= 1.5kΩ

F

V

L

S

= 1.5kΩ

F

V

L

S

= +2

= 300pF

= 5Ω

= 300pF

= 5Ω

1

10

100

1000

1

10

100

1000

FREQUENCY (MHz)

Figure 10. Small Signal Frequency Response vs. Case Temperature, A_V= +2,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.5 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 13. Large Signal Frequency Response vs. Case Temperature, A_V= +2,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.5 kΩ, C_L= 300 pF, R_S= 5 Ω

21

–20°C

+25°C

18

+100°C

15

12

9

15

12

9

6

3

0

V

R

A

C

R

= ±20V

V

R

A

C

R

= ±5V

S

= 20V p-p

= 2V p-p

OUT

–3

–6

–9

–3

–6

–9

= 1.21kΩ

F

V

L

S

F

V

L

S

= +5

= 300pF

= 5Ω

= 300pF

= 5Ω

1

10

100

1000

1

10

100

1000

FREQUENCY (MHz)

Figure 11. Small Signal Frequency Response vs. Case Temperature, A_V= +5,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 14. Large Signal Frequency Response vs. Case Temperature, A_V= +5,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

27

–20°C

+25°C

24

21

24

21

+100°C

18

17

12

9

18

15

12

9

6

V

R

A

C

R

= ±5V

OUT

= 1.21kΩ

= +10

= 300pF

= 5Ω

V

R

A

C

R

= ±20V

S

= 2V p-p

= 20V p-p

OUT

3

0

3

0

= 1.21kΩ

F

V

L

S

F

V

L

S

= +10

= 300pF

= 5Ω

–3

1

10

100

1000

1

10

100

1000

FREQUENCY (MHz)

Figure 15. Large Signal Frequency Response vs. Case Temperature, A_V= +10,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 12. Small Signal Frequency Response vs. Case Temperature, A_V= +10,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Rev. 0 | Page 9 of 24

ADA4870

Data Sheet

27

24

21

18

15

12

9

27

24

21

18

15

12

9

6

V

R

A

C

R

= ±5V

V

R

A

C

R

= ±20V

S

= 2V p-p

= 20V p-p

3

0

3

OUT

= 1.21kΩ

F

V

L

S

F

V

L

S

= −10

= –10

0

= 1000pF

= 5Ω

= 1000pF

= 5Ω

–3

1

10

100

1000

1

10

100

1000

FREQUENCY (MHz)

Figure 16. Small Signal Frequency Response, A_V= −10,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 1000 pF, R_S= 5 Ω

Figure 19. Large Signal Frequency Response, A_V= −10,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 1000 pF, R_S= 5 Ω

21

–20°C

+25°C

+100°C

+25°C

18

15

12

9

18

+100°C

15

12

9

6

3

0

V

R

A

R

= ±5V

V

R

A

R

= ±20V

S

–3

–6

–9

–3

–6

–9

S

= 2V p-p

= 20V p-p

OUT

= 1.21kΩ

F

V

L

F

V

L

= −5

= –5

= 50Ω

1

10

100

1000

1

10

100

1000

FREQUENCY (MHz)

Figure 17. Small Signal Frequency Response vs. Case Temperature, A_V= −5,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, R_L= 50 Ω

Figure 20. Large Signal Frequency Response vs. Case Temperature, A_V= −5,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, R_L= 50 Ω

21

–20°C

+25°C

18

+100°C

R

A

= 1.21kΩ

F

V

= –5

15

12

9

15

12

9

R

A

= 1.5kΩ

= +2

F

V

6

3

0

V

R

A

R

= ±20V

S

OUT

–3

–6

–9

–3

–6

–9

= 20V p-p

V

= ±20V

S

= 1.21kΩ

V

= 2V p-p

F

V

L

OUT

C

R

= −5

= 300pF

= 5Ω

L

S

= 20Ω

1

10

100

1000

1M

10M

100M

1G

FREQUENCY (MHz)

FREQUENCY (Hz)

Figure 18. Large Signal Frequency Response vs. Case Temperature, A_V= −5,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, R_L= 20 Ω

Figure 21. Small Signal Frequency Response vs. Case Temperature,

V_S= 20 V, V_OUT= 2 V p-p, C_L= 300 pF, R_S= 5 Ω

Rev. 0 | Page 10 of 24

Data Sheet

ADA4870

15

10

5

2.0

–20°C

+25°C

+100°C

–20°C

+25°C

+100°C

1.5

1.0

0.5

0

–0.5

–1.0

–1.5

–2.0

–5

–10

–15

V

= ±5V

V

= ±20V

= 1.21kΩ

= –2

= 300pF

= 5Ω

S

R

A

C

R

= 1.21kΩ

= –2

R

A

C

R

F

V

L

S

F

V

L

S

= 300pF

= 5Ω

TIME (25ns/DIV)

Figure 22. Small Signal Pulse Response vs. Case Temperature, A_V= −2,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 25. Large Signal Pulse Response vs. Case Temperature, A_V= −2,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

2.0

15

–20°C

+25°C

+100°C

–20°C

+25°C

+100°C

1.5

1.0

10

5

0.5

0

–0.5

–1.0

–1.5

–2.0

–5

V

= ±5V

V

= ±20V

= 1.21kΩ

= –5

= 300pF

= 5Ω

S

R

A

C

R

= 1.21kΩ

= –5

–10

–15

R

A

C

R

F

V

L

S

F

V

L

S

= 300pF

= 5Ω

TIME (25ns/DIV)

Figure 23. Small Signal Pulse Response vs. Case Temperature, A_V= −5,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 26. Large Signal Pulse Response vs. Case Temperature, A_V= −5,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

15

2.0

–20°C

+25°C

+100°C

10

–20°C

+25°C

+100°C

1.5

1.0

5

0

0.5

0

–0.5

–1.0

–1.5

–2.0

–5

V

= ±5V

V

= ±20V

= 1.21kΩ

= –10

= 300pF

= 5Ω

S

–10

–15

R

A

C

R

= 1.21kΩ

= –10

R

A

C

R

F

V

L

S

F

V

L

S

= 300pF

= 5Ω

TIME (25ns/DIV)

Figure 24. Small Signal Pulse Response vs. Case Temperature, A_V= −10,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 27. Large Signal Pulse Response vs. Case Temperature, A_V= −10,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Rev. 0 | Page 11 of 24

ADA4870

Data Sheet

2.0

15

10

5

–20°C

+25°C

+100°C

–20°C

+25°C

+100°C

1.5

1.0

0.5

0

–0.5

–1.0

–1.5

–2.0

–5

–10

–15

V

= ±5V

= 1.5kΩ

= +2

V

= ±20V

= 1.5kΩ

= +2

S

R

A

C

R

A

C

R

F

V

L

S

F

V

L

S

= 300pF

= 5Ω

= 300pF

= 5Ω

TIME (25ns/DIV)

Figure 28. Small Signal Pulse Response vs. Case Temperature, A_V= +2,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.5 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 31. Large Signal Pulse Response vs. Case Temperature, A_V= +2,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.5 kΩ, C_L= 300 pF, R_S= 5 Ω

2.0

15

–20°C

+25°C

+100°C

10

–20°C

+25°C

+100°C

1.5

1.0

0.5

5

0

–0.5

–1.0

–5

V

= ±5V

V

= ±20V

= 1.21kΩ

= +5

= 300pF

= 5Ω

S

R

A

C

R

= 1.21kΩ

= +5

–10

–15

R

A

C

R

F

V

L

S

F

V

L

S

–1.5

–2.0

= 300pF

= 5Ω

TIME (25ns/DIV)

Figure 29. Small Signal Pulse Response vs. Case Temperature, A_V= +5,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 32. Large Signal Pulse Response vs. Case Temperature, A_V= +5,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

2.0

15

–20°C

+25°C

+100°C

–20°C

+25°C

+100°C

10

1.5

1.0

5

0

0.5

0

–0.5

–1.0

–1.5

–2.0

–5

V

= ±5V

V

= ±20V

= 1.21kΩ

= +10

S

R

A

C

R

= 1.21kΩ

= +10

–10

–15

R

A

C

R

F

V

L

S

F

V

L

S

= 300pF

= 5Ω

= 300pF

= 5Ω

TIME (25ns/DIV)

Figure 30. Small Signal Pulse Response vs. Case Temperature, A_V= +10,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 33. Large Signal Pulse Response vs. Case Temperature, A_V= +10,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 300 pF, R_S= 5 Ω

Rev. 0 | Page 12 of 24

Data Sheet

ADA4870

15

10

5

2.0

1.5

1.0

0.5

0

–0.5

–1.0

–1.5

–2.0

–5

–10

–15

V

= ±20V

= 1.5kΩ

= +2

= 1000pF

= 5Ω

V

= ±5V

S

R

A

C

R

A

C

R

= 1.5kΩ

= +2

F

V

L

S

F

V

L

S

= 1000pF

= 5Ω

TIME (40ns/DIV)

Figure 34. Small Signal Pulse Response, A_V= +2,

Figure 37. Large Signal Pulse Response, A_V= +2,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.5 kΩ, C_L= 1000 pF, R_S= 5 Ω

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.5 kΩ, C_L= 1000 pF, R_S= 5 Ω

2.0

15

1.5

1.0

10

5

0.5

0

–0.5

–1.0

–1.5

–2.0

–5

V

= ±5V

V

= ±20V

= 1.21kΩ

= –10

= 1000pF

= 5Ω

S

R

A

C

R

= 1.21kΩ

= –10

R

A

C

R

F

V

L

S

–10

–15

F

V

L

S

= 1000pF

= 5Ω

TIME (40ns/DIV)

Figure 35. Small Signal Pulse Response, A_V= −10,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 1000 pF, R_S= 5 Ω

Figure 38. Large Signal Pulse Response, A_V= −10,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 1000 pF, R_S= 5 Ω

2.0

15

1.5

1.0

10

5

0.5

0

–0.5

–1.0

–1.5

–2.0

–5

V

= ±5V

= 1.5kΩ

= +2

= 1µF

= 5Ω

V

= ±20V

= 1.5kΩ

= +2

= 1µF

= 5Ω

S

R

A

C

R

A

C

R

F

V

L

S

–10

–15

F

V

L

S

TIME (25µs/DIV)

Figure 36. Small Signal Pulse Response, A_V= +2,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.5 kΩ, C_L= 1 μF, R_S= 5 Ω

Figure 39. Large Signal Pulse Response, A_V= +2,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.5 kΩ, C_L= 1 μF, R_S= 5 Ω

Rev. 0 | Page 13 of 24

ADA4870

Data Sheet

2.0

15

10

5

1.5

1.0

0.5

0

–0.5

–1.0

–1.5

–2.0

–5

–10

–15

V

= ±20V

= 1.21kΩ

= –10

V

= ±5V

= 1.21kΩ

= –10

= 1µF

= 5Ω

S

R

A

C

R

A

C

R

F

V

L

S

F

V

L

S

= 1µF

= 5Ω

TIME (25µs/DIV)

Figure 40. Small Signal Pulse Response, A_V= −10,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, C_L= 1 μF, R_S= 5 Ω

Figure 43. Large Signal Pulse Response, A_V= −10,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, C_L= 1μF, R_S= 5 Ω

15

2.0

1.5

–20°C

+25°C

+100°C

–20°C

+25°C

+100°C

10

5

1.0

0.5

0

–0.5

–1.0

–1.5

–2.0

–5

–10

–15

V

= ±20V

= 1.21kΩ

= –5

V

= ±5V

= 1.21kΩ

= –5

S

R

A

R

A

R

F

V

L

F

V

L

= 50Ω

TIME (25ns/DIV)

Figure 44. Large Signal Pulse Response vs. Case Temperature, A_V= −5,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, R_L= 50 Ω

Figure 41. Small Signal Pulse Response vs. Case Temperature, A_V= −5,

V_S= 5 V, V_OUT= 2 V p-p, R_F= 1.21 kΩ, R_L= 50 Ω

140

120

100

80

200

150

100

50

15

–20°C

+25°C

+100°C

10

PHASE

5

0

TRANSIMPEDANCE

60

0

40

–50

–100

–150

–200

–5

20

V

= ±20V

= 1.21kΩ

= –5

–10

–15

S

0

R

A

R

F

V

L

= 20Ω

–20

1k

10k

100k

1M

10M

100M

1G

TIME (25ns/DIV)

FREQUENCY (Hz)

Figure 42. Large Signal Pulse Response vs. Case Temperature, A_V= −5,

V_S= 20 V, V_OUT= 20 V p-p, R_F= 1.21 kΩ, R_L= 20 Ω

Figure 45. Open-Loop Transimpedance and Phase vs. Frequency

Rev. 0 | Page 14 of 24

Data Sheet

ADA4870

–10

–20

HD2 2V p-p, V = ±5V

S

HD3 2V p-p, V = ±5V

–20

–30

S

HD2 20V p-p, V = ±20V

S

HD2 20V p-p, V = ±20V

S

HD3 20V p-p, V = ±20V

–30

S

–40

–50

–60

–70

–80

–90

–100

–110

–120

–100

–110

–120

0.01

0.1

1

10

0.01

0.1

1

10

FREQUENCY (MHz)

Figure 46. Harmonic Distortion vs. Frequency, C_L= 300 pF, R_S= 5 Ω,

R_F= 1.21 kΩ, A_V= −10

Figure 49. Harmonic Distortion vs. Frequency, R_L= 25 Ω,

R_F= 1.21 kΩ, A_V= −10

–60

HD2, C = 300pF, R = 5Ω

L

S

HD3, C = 300pF, R = 5Ω

L

S

HD2, R = 25Ω

HD3, R = 25Ω

–70

–80

–70

–80

L

–90

–100

–110

–120

–100

–110

–120

HD2, C = 300pF, R = 5Ω

L

S

HD3, C = 300pF, R = 5Ω

L

S

HD2, R = 25Ω

HD3, R = 25Ω

L

0

5

10

(V p-p)

15

20

0

5

10

(V p-p)

15

20

V

OUT

Figure 47. Harmonic Distortion vs. V_OUT, V_S= 20 V, Frequency = 100 kHz,

R_F= 1.21 kΩ, A_V= −10

Figure 50. Harmonic Distortion vs. V_OUT, V_S= 20 V, Frequency = 1 MHz,

R_F= 1.21 kΩ, A_V= −10

–30

–40

–50

–60

HD2, C = 300pF, R = 5Ω

L

S

HD3, C = 300pF, R = 5Ω

L

S

HD2, R = 25Ω

HD3, R = 25Ω

L

–40

–50

–60

–70

HD2, C = 300pF, R = 5Ω

L

S

HD3, C = 300pF, R = 5Ω

HD2, R = 25Ω

L

HD3, R = 25Ω

L

–70

0

5

10

(V p-p)

15

20

0

5

10

(V p-p)

15

20

V

OUT

Figure 48. Harmonic Distortion vs. V_OUT, V_S= 20 V, Frequency = 10 MHz,

R_F= 1.21 kΩ, A_V= −10

Figure 51. Harmonic Distortion vs. V_OUT, V_S= 20 V, Frequency = 30 MHz,

R_F= 1.21 kΩ, A_V= −10

Rev. 0 | Page 15 of 24

ADA4870

Data Sheet

20

15

10

5

20

15

10

5

4,000

3,000

2,000

1,000

0

4,000

3,000

2,000

1,000

0

V

OUT

SLEW RATE

0

–5

–10

–15

–20

–1,000

–2,000

–3,000

–4,000

–5

–10

–15

–20

–1,000

–2,000

–3,000

–4,000

TIME (45ns/DIV)

Figure 52. Large Signal Instantaneous Slew Rate, A_V= +2,

V_S= 20 V, R_F= 1.5 kΩ, C_L= 300 pF, R_S= 5 Ω

Figure 55. Large Signal Instantaneous Slew Rate, A_V= +2,

V_S= 20 V, R_F= 1.5 kΩ, R_L= 25 Ω

30

25

6

5

4

3

2

1

0

–

3.5

V

= ±20V

= +5

= 50Ω

S

V

L

3.0

2.5

A

R

+100°C

+25°C

–20°C

V

OUT

IN

20

2.0

15

V

– V

EE

OUT

1.5

10

1.0

5

0.5

0

–0.5

–1.0

–1.5

–2.0

–2.5

–3.0

–3.5

–5

1

2

3

4

5

6

–10

–15

–20

–25

–30

V

– V

CC

OUT

–20°C

+25°C

+100°C

10

100

1k

TIME (150ns/DIV)

R

(Ω)

LOAD

Figure 53. Output Overdrive Recovery, V_S= 20 V, A_V= +5, R_L= 50 Ω

Figure 56. Output Headroom vs. R_LOADOver Case Temperature, V_S= 20 V

100

10000

V

= ±20V

= 1.21kΩ

= +1

V

= ±20V

= 1.21kΩ

= +1

S

F

V

S

F

V

SD

ON

R

A

R

A

10

1

1000

100

10

0.1

0.01

1

0.1

1

10

100

1000

1

10

100

1000

FREQUENCY (MHz)

Figure 54. Enabled Closed-Loop Output Impedance vs. Frequency

Figure 57. Disabled Closed-Loop Output Impedance vs. Frequency

Rev. 0 | Page 16 of 24

Data Sheet

ADA4870

0

–10

–20

–30

–40

–50

–60

–70

–80

+PSR

–PSR

V

= ±20V

= ±5V

S

–10

–20

–30

–40

–50

–60

–70

–80

100

1k

10k

100k

1M

10M

100M

100

1k

10k

100k

1M

10M

100M

FREQUENCY (Hz)

Figure 61. Power Supply Rejection (PSR) vs. Frequency, V_S= 20 V

Figure 58. Common-Mode Rejection vs. Frequency

1000

100

INN

10

INP

1

10

100

1k

10k

100k

1M

10M

1

10

100

1k

10k

100k

1M

10M

FREQUENCY (Hz)

Figure 62. Input Current Noise vs. Frequency

Figure 59. Input Voltage Noise vs. Frequency

50

40

15

10

V

= ±10V

S

30

V

= ±5V

S

20

5

0

10

V

= ±20V

S

OUT

0

–10

–20

–30

–40

–50

–5

SD

–10

–15

–20 –16 –12

–8

–4

0

4

8

12

16

20

TIME (1µs/DIV)

V

(V)

ICM

Figure 63. Input Common-Mode Voltage Range

Figure 60. Turn-On/Turn-Off Time, V_S= 10 V

Rev. 0 | Page 17 of 24

ADA4870

Data Sheet

1

3500

3000

2500

2000

1500

1000

500

V

= ±5V

= ±20V

S

0

V

= ±20V

S

–1

–2

–3

–4

–5

V

= ±5V

45

S

0

–10

–6

0

–8

–6

–4

–2

0

2

4

6

8

10

25

65

85

V

(mV)

TEMPERATURE (°C)

S

Figure 67. Input Offset Voltage Distribution, V_S= 5 V,

V_S= 20 V

Figure 64. Input Offset Voltage vs. Temperature, V_S= 5 V,

V_S= 20 V

14

10

6

35

30

25

20

15

10

5

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

INP, V = ±5V

S

V

= ±20V

= ±5V

S

INP, V = ±20V

S

V

S

V

= ±20V

= ±5V

S

2

–2

–6

–10

–14

V

S

INN, V = ±5V

S

INN, V = ±20V

S

0

25

45

65

85

0

25

45

65

85

TEMPERATURE (°C)

Figure 68. Input Bias Current vs. Temperature, V_S= 5 V, V_S= 20 V

Figure 65. Quiescent Supply Current (I_q) vs. Temperature, V_S= 5 V, V_S= 20 V

SD

)

(Enabled/Disabled via

40

20

ENABLED

0

–20

–40

–60

–80

–100

–120

–140

DISABLED P = 10dBm

IN

DISABLED P = 0dBm

IN

1k

10k

100k

1M

10M

100M

1G

FREQUENCY (Hz)

Figure 66. Forward Isolation vs. Frequency for 0 dBm and 10 dBm Input Levels

SD ON

(Disabled via or

)

Rev. 0 | Page 18 of 24

Data Sheet

ADA4870

APPLICATIONS INFORMATION

ON, INITIAL POWER-UP, AND SHORT-CIRCUIT

Table 6. Recommended R_FValues

Closed-Loop

Gain (V/V)

ON

After initial power-up, the

pin must be pulled low to ensure

R_F(Ω)

2000

1210

1500

1210

R_G(Ω)

Open

1210

1500

604

C_L(pF)

300

R_S(Ω)

ON

that the amplifier is turned on. Subsequently, floating the

pin enables the short-circuit protection feature while the

+1

−1

+2

−2

+5

+10

5

ON

amplifier remains on. While

protection feature is disabled.

is held low, the short-circuit

When a short-circuit condition is detected, the amplifier is

disabled, the supply current drops to about 5 mA, and the TFL

pin outputs a dc voltage of ~300 m V. To turn the amplifier back

on after a short-circuit event, follow the sequence for initial

power-up.

301

133

300

CAPACITIVE LOAD DRIVING

When driving a capacitive load (C_L), the amplifier output resistance

and the load capacitance form a pole in the transfer function of

the amplifier. This additional pole reduces phase margin at

higher frequencies and, if left uncompensated, can result in

excessive peaking and instability. Placing a small series resistor (R_S)

between the amplifier output and C_L(as shown in Figure 69)

allows the ADA4870 to drive capacitive loads beyond 1 μF.

Figure 70 shows the series resistor value vs. capacitive load for a

maximum of 1 dB peaking in the circuit of Figure 69. For large

capacitive loads, R_Svalues of less than 0.3 Ω are not

recommended.

ON

Pulling the

pin high disables the amplifier and causes the

supply current to drop to about 5 mA, as if a short-circuit

condition had been detected.

ON

The impedance at the

pin is ~20 kΩ. Lay out the PCB trace

to avoid noise coupling into it and triggering a

ON

leading to

false event. A 1 nF capacitor between

and V_EEis recommended

ON

to help shunt noise away from

.

THERMAL PROTECTION

In addition to short-circuit protection, the ADA4870 is also

protected against excessive die temperatures.

Figure 71 shows the small signal bandwidth (SSBW) vs. C_Lwith

corresponding R_Svalues from Figure 70.

During normal operation, the TFL pin outputs a dc voltage

(referenced to V_EE) ranging from 1.5 V to 1.9 V that is relative to

die temperature. The voltage on TFL changes at approximately

−3 mV/°C and can be used to indicate approximate increases in

die temperature. When excessive die temperatures are detected,

the amplifier switches to an off state, dropping the supply current to

approximately 5 mA, and TFL continues to report a voltage

relative to die temperature. When the die temperature returns

to an acceptable level, the amplifier automatically resumes

normal operation.

50Ω

V

IN

R

S

C

L

1.5kΩ

Figure 69. Circuit for Capacitive Load Drive

8

7

6

5

4

3

2

1

0

SHUTDOWN (SD)

The ADA4870 is equipped with a power saving shutdown feature.

SD

Pulling

quiescent current to approximately 750 µA. When turning the

SD

low places the amplifier in a shutdown state, reducing

amplifier back on from the shutdown state, pull the

pin high

pin low. Following this sequence ensures

ON

and then pull the

ON

power-on. Afterwards, the

short-circuit protection.

pin can be floated to enable

10p

100p

1n

10n

100n

1µ

C

(F)

L

SD

floating.

Pull

high or low; do not leave

Figure 70. R_Svs. C_Lfor Maximum 1 dB Peaking for Circuit from Figure 69

FEEDBACK RESISTOR SELECTION

The feedback resistor value has a direct impact on the stability

and closed-loop bandwidth of current feedback amplifiers.

Table 6 provides a guideline for the selection of feedback

resistors for some common gain configurations.

Rev. 0 | Page 19 of 24

ADA4870

Data Sheet

9

The total power dissipation in the amplifier is the sum of the

power dissipated in the output stage plus the quiescent power.

The average power for an amplifier processing sine signals is

computed by Equation 1. Equation 2 can be used to compute the

peak power of a sine wave and can be used to compute the

continuous power dissipation of dc output voltages where V_PEAKis

the dc load voltage. These equations assume symmetrical supplies

and a load referred to midsupply.

6

3

0

–3

–6

C

_L= 330pF, R_S= 6.8Ω

C_L= 1nF, R_S= 4Ω

2

















–9

–12

–15

V_CCV_PEAK

V_PEAK

C_L= 3.3nF, R_S= 2.5Ω

C_L= 10nF, R_S= 1.4Ω

C_L= 33nF, R_S= 0.7Ω

C_L= 100nF, R_S= 0.3Ω

2

(1)

P_{AVG , SINE}

=

(

V_S× I _q

)

+

×

–

















π

R_L

2 R_L

C_L= 1µF, R_S= 0.3Ω

0.1

1

10

100

FREQUENCY (MHz)





V_PEAK

(2)





P_PEAK

=

(

V_S

×

I

)

+

(

V_S– V_PEAK×

)

q

Figure 71. Small Signal Bandwidth for Various C_Land R_SValues from Figure 70

R_L





HEAT AND THERMAL MANAGEMENT

where

V_Sis the total supply voltage (V_CC– V_EE).

I_qis the amplifier quiescent current.

High output current amplifiers like the ADA4870 generate heat,

instantaneous or continuous, depending on the signal being

processed. Properly applied thermal management techniques

move heat away from the ADA4870 die and help to maintain

acceptable junction temperatures (T_J). A highly conductive

thermal path from the slug of the PSOP_3 package to the

ambient air is required to obtain the best performance at the

lowest T_J.

A graphical representation of the P_{AVG, SINE}and P_PEAKpower

equations is shown in Figure 73. The power curves were generated

for the ADA4870 operating from 20 V supplies and driving a

20 Ω load. The quiescent power intersects the vertical axis at

~1.3 W when V_OUTis at 0 V or midsupply. The graphs stop at

the output swing limit of 18 V.

POWER DISSIPATION

For dc analysis, peak power dissipation occurs at V_OUT= V_CC/2,

while the maximum average power for sine wave signals occurs

at V_OUT= 2V_CC/π.

The first step in identifying a thermal solution is to compute the

power generated in the amplifier during normal operation. The

schematic in Figure 72 shows a simplified output stage of the

ADA4870. The most significant heat is generated by the output

stage push-pull pair, particularly when driving heavy loads.

7

PEAK (W)

6

V

CC

5

AVG, SINE (W)

4

3

2

1

0

V

OUT

R

L

GND

0

5

10

15

20

V

EE

V

(V)

OUT

Figure 72. Simplified Output Stage

Figure 73. Average Sine and Peak Power vs. V_OUT, V_S= 20 V, R_L= 20 Ω

Rev. 0 | Page 20 of 24

Data Sheet

ADA4870

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

SAFE OPERATING AREA

MAXIMUM T = 150°C

J

The safe operating area (SOA) is a curve of output current vs.

output stage collector-emitter voltage (V_CE), under which the

amplifier can operate at a safe junction temperature (T_J). The

area under the curves of Figure 74 shows the operational

boundaries of the ADA4870 for the PCB of Figure 75 that

maintains a T_J≤ 150°C. The SOA curves of Figure 74 are unique

to the conditions under which they were developed, such as

PCB, heat sink, and ambient temperature.

25°C WITH VHS-45

25°C NO HEATSINK

85°C WITH VHS-95

85°C WITH VHS-45

85°C NO HEATSINK

Two heat sinks (VHS-45 and VHS-95) were used in the evaluation.

Both were assembled to the PCB using CT40-5 thermal interface

material.

0

2

4

6

8

10

12

14

16

18

20

OUTPUT STAGE V (V)

All testing was done in a still-air environment. Forced air

convection in any of the test cases effectively lowers θ_JAand

moves the corresponding curve toward the upper right,

expanding the SOA. For more information on the ADA4870

evaluation board, see the ADA4870 User Guide.

CE

Figure 74. Safe Operating Area for Evaluation Board from Figure 75 at 25°C

and 85°C Ambient Temperature With and Without Heat Sink, No Air Flow

In Figure 74, the horizontal line at 1 A is the output current

drive of the ADA4870. The curved section maintains a fixed

power dissipation that results in a junction temperature (T_J) of

150°C or less. Note that the x-axis is the output stage V_CE(V_CC

V_OUTor V_OUT– V_EE) developed across the relevant output

transistor of Figure 72 and ends at a maximum V_CEof 20 V.

−

EXPOSED PAD LANDING VIAS

COUNT: 136

FILL: AE3030

DIAMETER: 12mil

PITCH: 35mil

2.45in (62mm)

6-LAYER HR370 PCB

WITH INTERNAL GROUND TOP/BOTTOM: 1.5oz

AND POWER PLANES INNER LAYERS: 1oz

COPPER

Figure 75. Details of the ADA4870 Evaluation Board

Rev. 0 | Page 21 of 24

ADA4870

Data Sheet

PRINTED CIRCUIT BOARD (PCB)

HEAT SINK SELECTION

All current feedback amplifiers, including the ADA4870, can be

affected by stray capacitance. Paying careful attention during

PCB layout can reduce parasitic capacitance and improve

overall circuit performance. Minimize signal trace lengths by

placing feedback and gain setting resistors as close as possible to

the amplifier.

A heat sink increases the surface area to ambient temperature

(T_A) and extends the power dissipation capability of the

ADA4870 and PCB combination. To maximize heat transfer

from the board to the heat sink, attach the heat sink to the PCB

using a high conductivity thermal interface material (TIM). The

heat sinks presented in the Safe Operating Area section and

Figure 74 are effective up to ~10 W in still air. If lower power

dissipation is anticipated and/or forced air convection is used, a

smaller heat sink may be appropriate. If the thermal resistance

of the chip (θ_JC), PCB (θ_CB), and TIM (θ_TIM) are known, use

Equation 3 to compute the thermal resistance (θ_HS) of the

required heat sink.

Additionally, for high output current amplifiers like the

ADA4870, lay out the PCB with heat dissipation in mind. A

good thermal design includes an exposed copper landing area

on the top side of the board on which to solder the thermal slug

of the PSOP3 package. The PCB should also provide an exposed

copper area on the bottom side to accommodate a heat sink.

Stitch the top and bottom layers together with an array of

plated-through thermal vias to facilitate efficient heat transfer

through the board. Thermal conductivity may be further

improved by using widely available via fill materials.









T_J– T_A

(3)

θ _HS

=

–

(

θ _JC+θ _CB+θ _TIM

)









P_DISS

POWER SUPPLIES AND DECOUPLING

THERMAL MODELING

The ADA4870 can operate from a single supply or dual supplies.

The total supply voltage (V_CC− V_EE) must be between 10 V and

40 V. Decouple each supply pin to ground using high quality,

low ESR, 0.1 μF capacitors. Place decoupling capacitors as close

to the supply pins as possible. Additionally, place 22 μF tantalum

capacitors from each supply to ground to provide good low

frequency decoupling and supply the needed current to support

large, fast slewing signals at the ADA4870 output.

Computational fluid dynamics (CFD) tools like FloTherm® can

be used to create layers of materials that include PCB construction,

thermal vias, thermal interface materials, and heat sinks, and

can predict junction temperature and/or junction to ambient

thermal resistance (θ_JA) for a given set of conditions. Table 7

shows an example of how θ_JAis affected by the addition of an

aluminum heat sink and forced convection. Figure 76 shows an

image of the model used to establish the thermal results in Table 7.

T

BOARD

T

CASE

T

CU SLUG

LEADS

DIE

JUNCTION

ADA4870

T

PLASTIC

Figure 76. Thermal Model Stack-Up for Data in Table 7

(Heat Sink Not Shown)

Table 7. Effects of Heat Sink and Forced Convection on θ_JA

Heat Sink Dimensions, L × W × Total Height (mm)

Heat Sink Base Thickness (mm)

No. of Fins

Air Flow (m/sec)

θ_JA(°C/W)

15.95

12.27

10.95

11.36

4.90

3.86

5.74

3.59

3.18

61 × 58, Exposed Copper on Board, No Heat Sink

30 × 30 × 24

61 × 58 × 24

Not applicable

3

Not applicable

10

0

1

2

0

1

2

0

1

2

Rev. 0 | Page 22 of 24

Data Sheet

ADA4870

1.5

1.0

COMPOSITE AMPLIFIER

When dc precision and high output current are required, the

ADA4870 can be combined with a precision amplifier such as

the ADA4637-1 to form a composite amplifier as shown in

Figure 77.

0.5

0

By placing the ADA4870 inside the feedback loop of the

ADA4637-1, the composite amplifier provides the high output

current of the ADA4870 while preserving the dc precision of

the ADA4637-1.

–0.5

–1.0

–1.5

ADA4637-1

ADA4870

V

= ±15V

= 300pF

= 10Ω

S

L

S

C

R

V

IN

50Ω

R

50Ω

S

V

OUT

TIME (100ns/DIV)

C

L

Figure 79. Composite Amplifier Small Signal Pulse Response

3.01kΩ

110Ω

1kΩ

15

6pF

A

= 10V/V

V

10

5

OUTPUT OFFSET <500µV

Figure 77. Composite Amplifier

Figure 78 shows the bandwidth of the composite amplifier at a

gain of 10. The offset voltage at the output is <500 μV.

0

The circuit can be tailored for different gains as desired.

Depending on the board parasitics, the 6 pF capacitor may need

to be empirically adjusted to optimize performance. Minimize

PCB stray capacitance as much as possible, particularly in the

feedback path.

–5

–10

–15

V

= ±15V

= 300pF

= 10Ω

S

L

S

C

R

The small signal and large signal pulse response is shown in

TIME (100ns/DIV)

Figure 79 and Figure 80, respectively.

Figure 80. Composite Amplifier Large Signal Pulse Response

25

20

15

10

C

R

OUT

= 300pF

= 10Ω

= 10V p-p

L

S

5

0

V

C

R

= 300pF

= 10Ω

= 1V p-p

L

S

–5

V

OUT

–10

–15

–20

–25

–30

–35

R

V

= 50Ω

L

= 1V p-p

OUT

0.1

1

10

FREQUENCY (MHz)

100

1000

Figure 78. Composite Amplifier Frequency Response

Rev. 0 | Page 23 of 24

ADA4870

Data Sheet

OUTLINE DIMENSIONS

1.10 MAX × 45°

13.00

9.00

1

10

PIN 1

6.20

5.80

14.20

BSC

11.00

BSC

11

20

BOTTOM VIEW

TOP VIEW

1.10 MAX

(2 PLACES)

15.90

BSC

2.90 MAX

(2 PLACES)

3.60

3.35

3.10

DETAIL A

1.00

0.90

0.80

SIDE VIEW

END VIEW

8°

0°

1.10

0.80

SEATING

PLANE

0.53

0.40

1.27

BSC

3.30

3.15

3.00

DETAIL A

3.60

3.35

3.10

0.10

0.05

0.00

0.32

0.23

0.30

0.20

0.10

COMPLIANT TO JEDEC STANDARDS MO-166-AA

Figure 81. 20-Lead Power SOIC, Thermally Enhanced Package [PSOP_3]

(RR-20-1)

Dimensions shown in millimeters

ORDERING GUIDE

Model¹

Temperature Range

−40°C to +85°C

Package Description

Package Option

ADA4870ARRZ

ADA4870ARRZ-RL

ADA4870ARR-EBZ

20-Lead PSOP_3

Evaluation Board

RR-20-1

¹Z = RoHs Compliant Part.

registered trademarks are the property of their respective owners.

D12125-0-5/14(0)

Rev. 0 | Page 24 of 24


型号：	ADA4870
厂家：	ADI
描述：	Ideal for driving high capacitive or low resistive loads
文件：	总25页 (文件大小：734K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

ADA4870 [ADI]

相关型号：

ADA4870-KGD-DF

ADA4870-KGD-WP

ADA4870ARR-EBZ

ADA4870ARRZ

ADA4870ARRZ-RL

ADA4891-1

ADA4891-1AR-EBZ

ADA4891-1ARJ-EBZ

ADA4891-1ARJZ

ADA4891-1ARJZ-R7

ADA4891-1ARJZ-RL

ADA4891-1ARZ