LOG200 Precision, High-Speed Logarithmic Amplifier

With Integrated Photodiode Bias

1 Features

• Ultra-fast transient response to low current levels:

– Settling time for 10nA to 100nA step:

240ns rising, 620ns falling (typ)

– Settling time for 100nA to 1μA step:

60ns rising, 150ns falling (typ)

• Wide dynamic range: 10pA to 10mA (180dB)

– Specified from 100pA to 10mA (160dB)

• High signal bandwidth:

– 20MHz at 10µA to 10mA

– 6.3MHz at 1μA

– 90kHz at 1nA

• High-accuracy transfer function:

– 0.2% max log conformity error (10nA to 100µA)

• Integrated reference current (1μA) and reference

voltages (2.5V and 1.65V)

• Additional auxiliary high-speed op amp for

differential ADC drive, single-ended gain or filter

blocks, and other peripheral functions

• Single supply (4.5V to 12.6V) or

dual supply (±2.25V to ±6.3V) operation

• Specified temperature range: –40°C to +125°C

• Small package options:

– 3mm × 3mm VQFN

– 1.6mm x 1.6mm DSBGA (Preview)

2 Applications

• Optical modules

• Inter-DC interconnect

• Optical network terminal unit

• Chemistry/gas analyzer

• Erbium-doped fiber optic amplifier (EDFA)

+

–

+

–

+

–

I2

I1

PD

Bias

IBIAS

VCM

+

–

REFGND

+

–

2.5V

1.65V

REF25

REF165

+

–

REFA

OUTA

OUTB

–IN

+IN

VS+

VS–

VS+

1μA

IREF

LOG200 Device Schematic

3 Description

The LOG200 is a wide-dynamic-range current-to-

voltage amplifier specifically designed to optimize

current measurements across 160dB of dynamic

range

with

unparalleled

accuracy

and

speed

for optical communications, medical diagnostics,

and industrial process-control measurements. The

LOG200 features two logarithmic amplifiers followed

by a high-accuracy differential amplifier that convert

current signals into a voltage representing the log-

compressed ratio of the two currents. The current

inputs are designed to feature a high-speed response

from one input, and a highly accurate reference

signal on the other input, allowing for a unique

combination of fast transient response and high

logarithmic conformity.

The LOG200 ratio is internally set to 250mV/

decade of current-to-voltage conversion. The device

integrates an uncommitted high-speed amplifier to

allow the output to be configured for differential or

filtered responses, with a fast settling time to drive

successive approximation analog-to-digital converters

(SAR ADCs). The LOG200 also features a separate

reference current and reference voltage designed to

configure the device for optimized input current and

common-mode voltages.

The LOG200 can be powered in a single-supply

(4.5V to 12.6V) or dual-supply (±2.25V to ±6.3V)

configuration and is specified from –40°C to +125°C.

Package Information

PART NUMBER

PACKAGE(1)

PACKAGE SIZE(2)

LOG200

RGT (VQFN, 16)

3mm × 3mm

YBH (DSBGA, 16)(3) 1.6mm × 1.6mm

(1)

For more information, see Section 10.

(2)

The package size (length × width) is a nominal value and

includes pins, where applicable.

(3)

Preview information (not Production Data).

LOG200

SBOSA28A – AUGUST 2023 – REVISED DECEMBER 2024

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. UNLESS OTHERWISE NOTED, this document contains PRODUCTION

DATA.