Datasheet MAX4238, MAX4239 (Maxim) - 7
| Manufacturer | Maxim |
| Pages / Page | 9 / 7 — Typical Operating Characteristics (continued). DC TO 10Hz NOISE. EMIRR … |
| File Format / Size | PDF / 1.3 Mb |
| Document Language | English |
Typical Operating Characteristics (continued). DC TO 10Hz NOISE. EMIRR vs. FREQUENCY. Offset Error Sources. Pin Description. PIN
Text Version of Document
MAX4238/MAX4239 Ultra-Low Offset/Drift, Low-Noise, Precision SOT23 Amplifiers
Typical Operating Characteristics (continued)
(VCC = 5V, VCM = 0V, RL = 10kΩ connected to VCC/2, SHDN = VCC, TA = +25°C, unless otherwise noted.)
DC TO 10Hz NOISE EMIRR vs. FREQUENCY
MAX4238/39 toc19 140 VCC = 5V, RFIN = 16dBm 120 MAX4238/39 toc21 100 80 OUT 0.6µV/div EMIRR (dB) 60 40 20 0 1s/div 10 100 1000 VCC = 2.5V FREQUENCY (MHz) VEE = -2.5V
Offset Error Sources Pin Description
To achieve very low offset, several sources of error common
PIN
to autozero-type amplifiers need to be considered. The
NAME FUNCTION
first contributor is the settling of the sampling capacitor.
TDFN SOT23 SO
This type of error is independent of input-source impedance, 1 1 6 OUT Amplifier Output or the size of the external gain-setting resistors. Maxim 2 2 4 GND Ground uses a patented design technique to avoid large changes 3 3 3 IN+ Noninverting Input in the voltage on the sampling capacitor to reduce settling time errors. 4 4 2 IN- Inverting Input The second error contributor, which is present in both Shutdown Input. Active-low autozero and chopper-type amplifiers, is the charge injection 5 5 1 SHDN shutdown, connect to VCC from the switches. The charge injection appears as current for normal operation. spikes at the input, and combined with the impedance 6 6 7 VCC Positive Power Supply seen at the amplifier’s input, contributes to input offset No Connection. Not voltage. Minimize this feedthrough by reducing the size of — — 5, 8 N.C. internally connected. the gain-setting resistors and the input-source impedance. Exposed Pad (TDFN only). A capacitor in parallel with the feedback resistor reduces — — — EP the amount of clock feedthrough to the output by limiting Connect EP to GND. the closed-loop bandwidth of the device.
Detailed Description
The design of the MAX4238/MAX4239 minimizes the The MAX4238/MAX4239 are high-precision amplifiers effects of settling and charge injection to allow specification that have less than 2.5µV of input-referred offset and low of an input offset voltage of 0.1µV (typ) and less than 1/f noise. These characteristics are achieved through a 2.5µV over temperature (-40°C to +85°C). patented autozeroing technique that samples and cancels
1/f Noise
the input offset and noise of the amplifier. The pseudorandom clock frequency varies from 10kHz to 15kHz, reducing 1/f noise, inherent in all semiconductor devices, is inversely intermodulation distortion present in chopper-stabilized proportional to frequency. 1/f noise increases 3dB/octave amplifiers. and dominates amplifier noise at lower frequencies. This noise appears as a constantly changing voltage in series with any signal being measured. The MAX4238/MAX4239 treat 1/f noise as a slow varying offset error, inherently canceling the 1/f noise. www.maximintegrated.com Maxim Integrated │ 7
Typical Operating Characteristics (continued)
(VCC = 5V, VCM = 0V, RL = 10kΩ connected to VCC/2, SHDN = VCC, TA = +25°C, unless otherwise noted.)
DC TO 10Hz NOISE EMIRR vs. FREQUENCY
MAX4238/39 toc19 140 VCC = 5V, RFIN = 16dBm 120 MAX4238/39 toc21 100 80 OUT 0.6µV/div EMIRR (dB) 60 40 20 0 1s/div 10 100 1000 VCC = 2.5V FREQUENCY (MHz) VEE = -2.5V
Offset Error Sources Pin Description
To achieve very low offset, several sources of error common
PIN
to autozero-type amplifiers need to be considered. The
NAME FUNCTION
first contributor is the settling of the sampling capacitor.
TDFN SOT23 SO
This type of error is independent of input-source impedance, 1 1 6 OUT Amplifier Output or the size of the external gain-setting resistors. Maxim 2 2 4 GND Ground uses a patented design technique to avoid large changes 3 3 3 IN+ Noninverting Input in the voltage on the sampling capacitor to reduce settling time errors. 4 4 2 IN- Inverting Input The second error contributor, which is present in both Shutdown Input. Active-low autozero and chopper-type amplifiers, is the charge injection 5 5 1 SHDN shutdown, connect to VCC from the switches. The charge injection appears as current for normal operation. spikes at the input, and combined with the impedance 6 6 7 VCC Positive Power Supply seen at the amplifier’s input, contributes to input offset No Connection. Not voltage. Minimize this feedthrough by reducing the size of — — 5, 8 N.C. internally connected. the gain-setting resistors and the input-source impedance. Exposed Pad (TDFN only). A capacitor in parallel with the feedback resistor reduces — — — EP the amount of clock feedthrough to the output by limiting Connect EP to GND. the closed-loop bandwidth of the device.
Detailed Description
The design of the MAX4238/MAX4239 minimizes the The MAX4238/MAX4239 are high-precision amplifiers effects of settling and charge injection to allow specification that have less than 2.5µV of input-referred offset and low of an input offset voltage of 0.1µV (typ) and less than 1/f noise. These characteristics are achieved through a 2.5µV over temperature (-40°C to +85°C). patented autozeroing technique that samples and cancels
1/f Noise
the input offset and noise of the amplifier. The pseudorandom clock frequency varies from 10kHz to 15kHz, reducing 1/f noise, inherent in all semiconductor devices, is inversely intermodulation distortion present in chopper-stabilized proportional to frequency. 1/f noise increases 3dB/octave amplifiers. and dominates amplifier noise at lower frequencies. This noise appears as a constantly changing voltage in series with any signal being measured. The MAX4238/MAX4239 treat 1/f noise as a slow varying offset error, inherently canceling the 1/f noise. www.maximintegrated.com Maxim Integrated │ 7
