Features

Integrated active load and 1 buffer gain; very low buffer power consumption; as low as 20 MW pads; use GPO control to reduce the power saving characteristics of the effective load current; high -speed buffer; 400; 400; 400; 400 MMS, -3 decibel bandwidth; 415V/μS conversion rate; fast settlement time is 1%, 2V step: 5NS; adjustable buffer width; push-pull output stage; adjustable contribution load current; small packaging: 1.6mm × 1.6mm × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × 0.55mm.

Application

CCD image sensor output buffer; digital camera camera.

General description

ADA4800 is an voltage buffer integrated with the active load. The buffer is a single -chip amplifier with low power consumption, high -speed, low noise, high conversion rate, fast and stable, and fixed gain, which is suitable for the application of charge coupling devices (CCD). For CCD applications, the source load current source (i) can load the output of the open source CCD sensor, and the buffer can drive the AFE load. The active current load can also be closed, using ADA4800 as a unit gain buffer. The buffer only consumes a static power of 20 MW. In an important application of power saving, the ADA4800 has a power -saving mode (see the power -saving mode 1), which further reduces the total current consumption. The bandwidth of the ADA4800 buffer can also be completely adjusted through the IDRV pin.

ADA4800 buffer adopts a push -pull output -level structure, providing driving current and maximum rotation capabilities for rising and down signal conversion. Under the setting of 5 millianges, it provides a bandwidth of 400 MMS, -3 decibels, which makes this buffer very suitable for CCD sensors from machine vision to digital camera applications.

ADA4800 is very suitable for 12 -bit and 14 -bit high -resolution simulation front end (AFE) inputs such as AD9928, AD9990, AD9920A, AD9923A, and AD997X series.

ADA4800's multifunctional allowance is seamlessly connected to many CCD sensors from different manufacturers.

ADA4800 is designed to work under the power supply voltage of as low as 4 V and 17 V. It has a 6-drawing LFCSP package of 1.6 mm × 1.6 mm × 0.55 mm, and the rated operating temperature range is -40 C to +85 C.

Absolutely maximum rated value

t 25 ° C, unless there is another instructions.

The stress higher than the absolute maximum rated value may cause permanent damage to the device. This is just a stress level; the function operation of the device in these or any other conditions is higher than the conditions shown in the operation.The section is not implicit. Long -term exposure to absolute maximum rated conditions may affect the reliability of the device.

Thermal resistance

θ is specified for the worst case, that is, the device welded in the surface of the surface in the circuit board.

pin configuration and function description

Typical performance features

t 25 ° C , V 7.5 V, V -7.5 V, R 249 kΩ connected V, V -4.5 V, r 10 kΩ connected v, v parallel end connection 49.9Ω to 0 V, R 1 kΩ and 22 pf parallel connection parallel , Line 10Ω to 0 V.

Operation theory [ 123]
ADA4800 is a buffer integrated with event load. Each element (active load and buffer) runs independently, as described below.

Set valid load current using pins 6 (ISF)

ISF pin to determine the value of a functional current load (IAL). Set the ISF current with Formula 1.

Among them: VISF reference pin 2. VISF can be an external voltage source, VCC or GPO output, as described in the following paragraphs.

RISF is an external resistance between ISF pin and VISF.

The contribution load current (input In-PIN) is proportional to iISF, which can be calculated through formula 2.

ADA4800 allows additional energy saving by reducing effective load current. The source load current can connect the ISF pin to any universal output (GPO) pins of the system microcontroller through the external resistance. GPO logic high enables the flow of effective load current. Application -vs may connect high-Z to the ISF pin and place the ADA4800 in the power-saving mode by turning off the effective load current.

FIG. 22 demonstrates the ADA4800 application configuration using this energy -saving function.

The external resistor connected between ISF and microcontroller GPO pins determines the current flowing input input pins. This current can be calculated with equation 1 and equation 2.

Use the pins 4 to set the bandwidth (IDRV)

IDRV pin to establish the ICC static current of the buffer. With the increase of ICC, power consumption and bandwidth have increased. Set the current with Formula 3.

Among them: viDRV refers to sales 2. VIDRV can be an external voltage source or VCC.

Ridrv is an external resistor between IDRV pin and VIDRV.

ICC current is directly proportional to IIDRV, which can be calculated by Formula 4.

Application of IDRV PIN -VS will turn off the buffer.

Application information

Open source CCD output buffer

ADA4800 has low power consumption, high conversion rate and fast stable time. It is a CCD sensor for open source code output configuration The ideal solution for output buffer. Figure 21 shows the typical application circuit of ADA4800 as a CCD sensor output buffer.

The output of the CCD is directly connected to the input terminal of the ADA4800, and its output terminal is coupled with the input end of the analog front end.

In order to reduce the influence of power noise coupling to the ISF and IDRV tube, use 0.1 μF cecug capacitor. In order to obtain the best performance, these capacitors are placed in the position closer to each foot.

Power saving mode

The buffer of ADA4800 only consumes a static power of 20 MW. In order to achieve a larger energy -saving effect, the ADA4800 active load current can be closed or reduced in the surveillance mode in the standby mode. FIG. 22 illustrates this energy -saving function as an open source CCD buffer configuration as an open source code. The power -saving mode allows the ISF pin to connect the ISF pin to any general output (GPO) pin to the system microcontroller through an external resistor, thereby logical control of the I current. GPO logic high enables input exchange current flow, and low logic disable input exchange current and assertive power saving mode.

FIG. 23 shows an example of ADA4800 energy -saving function.

FIG. 23 provides three combinations of i. The choice of i is controlled by logical signal applied to the GPO1 and GPO2 tubes. Table 5 summarizes i selection.

Power sources

We must pay attention to bypassing the power pins of ADA4800. Using high -quality capacitors with low -equation series resistors (ESR), such as multi -layer ceramic capacitors (MLCC), minimize power supply ripples and power consumption. A large, usually a capacitor of 2.2 μF to 47μF, is located near ADA4800, and needs to provide good decoupling for low -frequency signals. The actual value is determined by the circuit's transient and frequency requirements. In addition, the 0.1 μF MLCC off -coupled power container should be as close to the power of the power as much as possible, and the distance does not exceed 1 inches. The ground return response immediately terminates on the ground surfaceEssenceSetting the circuit of bypass capacitors at a near -load circuit can minimize the ground circuit and improve performance.

Power sorting

All I/O pins are protected by ESD, and the internal back -to -back diode is connected to VCC and GND, as shown in Figure 24.In the case of ADA4800 power shutdown (V 0V), the voltage on the I/O pins can open the protective diode and cause permanent damage or damage IC.In order to prevent this during the period of power, before the VCC is fully connected and fixed, the voltage should not be applied to any I/O pin.When turning off the power, remove the I/O pins voltage or reduce it to 0 V before the VCC closure.

In the case of voltage on the I/O pins of V 0V, the power or adding string of connected resistance should limit the current to 5mA or below.

appearance size