ANALOG DEVICES ADL5315 Service Manual

Precision Wide Range (3 nA to 3 mA)

FEATURES

Accurately mirrors input current (1:1 ratio) over 6 decades

Linearity 1% from 3 nA to 3 mA

Stable mirror input voltage

Voltage held 1 V below supply using internal reference

or can be set externally

Adjustable input current limit

2.7 V to 8 V single-supply operation Miniature 8-lead LFCSP (2 mm × 3 mm)

APPLICATIONS

Optical power monitoring from a single photodiode General voltage biasing with precision current monitoring Voltage-to-current conversion

High-Side Current Mirror

ADL5315

FUNCTIONAL BLOCK DIAGRAM

ADL5315

VOLTAGE

REFERENCE

COMM

20kΩ

SREF

VSET NC

2 7

INPT

CURRENT

LIMITING

CURRENT

MIRROR

1:1

Figure 1.

RLIM

VPOS

IOUT

05694-001

GENERAL DESCRIPTION

The ADL5315 is a wide input current range, precision high-side current mirror featuring a stable and user-adjustable input voltage. It is optimized for use with PIN photodiodes, but its flexibility and wide operating range make it suitable for a broad array of additional applications. Over the 3 nA to 3 mA range, the current sourced from the INPT pin is accurately mirrored with a 1:1 ratio and sourced from the IOUT output pin. In a typical photodiode application, the output drives a currentinput logarithmic amplifier to produce a linear-in-dB output representing the optical power incident upon the photodiode. For linear voltage output, a single resistor to ground is all that is required. The photodiode anode can be connected to a high speed transimpedance amplifier for the extraction of the data stream. The voltage at the INPT pin is temperature stable with respect to the voltage at the VSET input pin, which it tracks. A temperature stable reference voltage is provided at the SREF pin, which, when tied to VSET, fixes the voltage at INPT 1.0 V below VPOS. VSET can also be driven from an external source.

The VSET input has very low input current and can be driven as low as the bottom rail, facilitating nonloading voltage-tocurrent conversion as well as minimizing dark current in photodiode applications.

The ADL5315 also features adjustable input current limiting using an external resistor from RLIM to VPOS. The maximum current sourced by INPT (and IOUT) can be set between 1 mA and 16 mA, beyond which the voltage at INPT falls rapidly from its setpoint. Connecting RLIM directly to VPOS provides basic input short-circuit protection with the default current limit of 16 mA typical.

The ADL5315 is available in a 2 mm × 3 mm, 8-lead LFCSP and is specified for operation from −40°C to +85°C.

Rev. 0

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Anal og Devices for its use, nor for any infringements of patents or ot her rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.

ADL5315

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

Noise Performance..................................................................... 10

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

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

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

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

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

Absolute Maximum Ratings............................................................ 4

ESD Caution.................................................................................. 4

Pin Configuration and Function Descriptions............................. 5

Typical Performance Characteristics ............................................. 6

Theory of Operation ........................................................................ 9

Bias Control Interface.................................................................. 9

REVISION HISTORY

10/05—Revision 0: Initial Version

Mirror Response Time............................................................... 10

Input Current Limiting.............................................................. 10

Applications..................................................................................... 11

Average Power Monitoring ....................................................... 11

Translinear Log Amp Interfacing............................................. 12

Extended Operating Range....................................................... 13

Using RLIM as a Secondary Monitor...................................... 13

Characterization Methods ........................................................ 14

Evaluation Board............................................................................ 16

Outline Dimensions....................................................................... 17

Ordering Guide .......................................................................... 17

Rev. 0 | Page 2 of 20

ADL5315

SPECIFICATIONS

= 5 V, V

POS

Table 1.

Parameter Conditions Min Typ Max Unit

CURRENT MIRROR OUTPUT IOUT (Pin 8)

Current Gain from INPT to IOUT 0.99 1.00 1.01 Current Gain from INPT to IOUT

Nonlinearity 3 nA < IPD < 3 mA 0.25 1.00 % Small Signal Bandwidth I

Wideband Noise at IPDM Specified Output Voltage Range 0 V I

× R

OUT

MIRROR INPUT, VOLTAGE CONTROL INPT (Pin 1), VSET (Pin 2), SREF (Pin 3)

Specified Input Current Range, I Specified VSET Voltage Range 2.7 V < V

6.5 V < V Incremental Gain from VSET to INPT 0.2 V < V Incremental Input Resistance at VSET V Input Bias Current at VSET V SREF Voltage, Relative to V

OVERCURRENT PROTECTION

INPT Current Limit V

V POWER SUPPLY VPOS (Pin 6)

Supply Voltage Range 2.7 8 V

Quiescent Current I

= 4 V, I

SET

Product I

OUT

= 3 µA, TA = 25°C, unless otherwise noted.

INPT

POS

−40°C < TA < +85°C

= 3 nA 1 kHz

INPT

= 3 μA 1 MHz

INPT

= 3 μA, C

INPT

= 3 μA 900

INPT

= 2.2 nF 20 nA rms

SET

0.97 1.00 1.03 A/A

− 1 V

POS

Flows from INPT pin 3n 3m A

< 6.5 V 0 V

POS

< 8 V V

POS

< 7.0 V 0.98 1 1.02 V/V

SET

= 4.0 V >100 GΩ

SET

= 4.0 V <30 pA

SET

2.7 V < V

INPT

< 8 V −1.04 −1.0 −0.97 V

POS

drops to 0 V, R drops to 0 V, R

= 0 Ω 16 mA

LIM

= 3 kΩ 6.4 8 9.6 mA

LIM

= 3 μA 1.8 2.2 mA = 3 mA 8.3 10.2 mA

− 6.5 V

POS

− 1 V

POS

− 1 V

POS

Rev. 0 | Page 3 of 20

ADL5315

ABSOLUTE MAXIMUM RATINGS

Table 2.

Parameter Rating

Supply Voltage 8 V Input Current at INPT 20 mA Internal Power Dissipation 500 mW θJA (Soldered Exposed Paddle) 80°C/W Maximum Junction Temperature 125°C Operating Temperature Range −40°C to +85°C Storage Temperature Range −65°C to +150°C Lead Temperature (Soldering 60 sec) 300°C

ESD CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.

Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Rev. 0 | Page 4 of 20

ADL5315

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

1INPT 2VSET

ADL5315

TOP VIEW

3SREF

(Not to Scale)

4COMM

NC = NO CONNECT

8 IOUT 7NC

6 VPOS

5 RLIM

05694-002

Figure 2. 8-Lead LFCSP

Table 3. Pin Function Descriptions

Pin No. Mnemonic Description

1 INPT Input Current. Pin sources current only. 2 VSET

3 SREF

Sets Voltage at INPT (Gain = 1). Range 0 V to V V

− 1 V. Optional shielding of INPT trace.

POS

Reference Voltage for VSET. Internally generated at V

− 1.0 V for V

POS

< 6.5 V. For V

POS

− 1.0 V through 20 kΩ. Can be shorted to VSET for

standard mirror operation. 4 COMM Analog Ground. 5 RLIM External Resistor to VPOS. Sets current limit at INPT from 1 mA to 16 mA. I

= 48 V/(R

LIM

6 VPOS Positive Supply (2.7 V to 8.0 V). 7 N/C Optional Shielding of IOUT Trace. No connection to die. 8 IOUT Output Current. Mirrors current at INPT with a gain of 1.0. Sources current only. PADDLE Internally connected to COMM, solder to ground.

≥ 6.5 V range, V

+ 3 kΩ).

LIM

− 6.5 V to

POS

Rev. 0 | Page 5 of 20

ADL5315

TYPICAL PERFORMANCE CHARACTERISTICS

= 5 V, V

POS

2.0

1.5

1.0

0.5

–0.5

LINEARITY (%)

–1.0

–1.5

–2.0

1n 10m

= V

, V

SET

SREF

–40°C 0°C +25°C +70°C +85°C

10n 100n 1μ 10μ 100μ 1m

Figure 3. I

Linearity vs. I

OUT

= 0 V, TA = 25°C, unless otherwise noted.

OUT

+25°C, +70°C, +85°C,

0°C, –40°C

(A)

INPT

for Multiple Temperatures,

INPT

Normalized to 25°C and I

INPT

= 3 µA

10m

100μ

10μ

1μ

100n

10n

–40°C +25°C +85°C

(A) I

2.0

1.5

1.0

0.5

OUT

05694-003

–0.5

LINEARITY (%)

–1.0

–1.5

–2.0

10n 100n 1μ 10μ 100μ 1m

1n 10m

Figure 6. I

Linearity vs. I

OUT

Normalized to V

–20

VS. I

INPT

VOLTAGE CONDITIONS

INPT

= 5 V, V

POS

, ALL

OUT

= 2.7V, V

POS

= 5V, V

POS

= 5V, V

POS

= 8V, V

POS

= 8V, V

POS

(A)

for Multiple Supply Conditions,

INPT

= V

SET

SREF

SET SET SET SET

, and I

SET

= V = 2V = V = 2V = V

INPT

SREF

= 3 µA

10m

100μ

10μ

1μ

100n

10n

(A)

OUT

05694-006

LINEARITY (%)

WIDEBAND CURRENT NOISE (%)

3.0

2.5

2.0

1.5

1.0

0.5

–1

–2

–3

Figure 4. I

10n 100n

Linearity vs. I

OUT

INPT

for Multiple Temperatures and

INPT

Devices Normalized to 25°C and I

= 3.0V

= 4.6V

POS

= 7.8V

POS

10n 100n 1μ 10μ 100μ 1m

POS

INPT

(A)

INPT

= 3 µA

10m1μ 10μ 100μ 1m

10m

05694-021

05694-016

–40

VARIATION (mV)

–60

INPT

–80

–100

–120

Figure 7. V

1nA

100pA

10pA

1pA

NSD (A rms/√Hz)

100fA

10fA

1fA

–40°C, V –40°C, V –40°C, V +25°C, V +25°C, V +25°C, V +85°C, V +85°C, V +85°C, V

10n 100n

Variation vs. I

INPT

Normalized to V

3.6mA

360μA

100Hz

1kHz 10kHz 100kHz 1MHz

POS POS POS POS POS POS POS POS POS

POS

= 2.7V, V = 5V, V = 5V, V = 2.7V, V = 5V, V = 5V, V = 2.7V, V = 5V, V = 5V, V

= 5 V, V

= V

SET

SREF

= 0V

SET

= V

SET

SREF

= V

SET

SREF

= 0V

SET

= V

SET

SREF

= V

SET

SREF

= 0V

SET

= V

SET

SREF

(A)

INPT

for Multiple Temperatures and Voltage,

INPT

= V

, I

SREF

INPT

= 3 µA and 25°C

SET

360nA

36nA

3.6nA

FREQUENCY

3.6μA

10m1μ 10μ 100μ 1m

36μA

10MHz

05694-005

05694-007

Figure 5. Output Wideband Current Noise as a Percentage of I

for Multiple Values of V

INPT

, C

= 2.2 nF, BW = 10 MHz

POS

SET

vs.

OUT

Rev. 0 | Page 6 of 20

Figure 8. Output Current Noise Density vs. Frequency for

Multiple Values of I

INPT

, V

POS

= 4.6 V, V

= V

, C

SREF

= 2.2 nF

SET

+ 14 hidden pages

ANALOG DEVICES ADL5315 Service Manual

FEATURES

APPLICATIONS

FUNCTIONAL BLOCK DIAGRAM

GENERAL DESCRIPTION

TABLE OF CONTENTS

REVISION HISTORY

SPECIFICATIONS

ABSOLUTE MAXIMUM RATINGS

ESD CAUTION

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

TYPICAL PERFORMANCE CHARACTERISTICS