Part A
ADS7843E
Burr Brown
- Lifecycle
- Active
- Stock
- 6691 PCS
- Package
- SSOP-16
- Series
- Data Acquisition - Touch Screen Controllers
Replacement verdict
Not a drop-in replacement
The ADS7844NB/1K and ADS7843E are not interchangeable despite sharing a similar 12-bit SAR architecture and SSOP-20 footprint. The ADS7844NB/1K is an 8-channel multiplexed ADC with a serial interface, while the ADS7843E is a dedicated 4-wire touch-screen controller with an integrated pen-interrupt output and on-chip reference drive. Their input topologies, control interfaces, and application roles differ fundamentally, so substituting one for the other is not feasible without a redesign.
Different input architecture
Different channel count
Different control interface
Different application function
Parts at a glance
Part B
ADS7844NB/1K
Texas Instruments
- Lifecycle
- Active
- Stock
- 5039 PCS
- Package
- SSOP-20
- Series
- Data Acquisition - Analog to Digital Converters (ADC)
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | ADS7844NB/1K | ADS7843E | Why it matters |
|---|---|---|---|
| Resolution (bits) | 12 | 12 | Both are 12-bit, so conversion resolution is equivalent for substitutability. |
| Number of input channels | 8 (single-ended) / 4 (differential) | 4 (single-ended) / 2 (differential) | The ADS7844 supports more channels, so it can handle additional signal inputs that the ADS7843 cannot. |
| Interface type | SPI / Serial | SPI / Serial | Both use a serial SPI interface, allowing similar microcontroller connectivity. |
| Supply voltage range | 2.7 V to 5.25 V | 2.7 V to 5.25 V | Identical supply range means both can operate from the same system rails. |
| Package / mounting | 20-SSOP (surface mount) | 16-SSOP (surface mount) | Different package sizes and pin counts affect PCB footprint and layout compatibility. |
| Typical application focus | General-purpose 8-channel ADC | Touch-screen controller ADC | The ADS7843 is optimized for touch-screen digitizer applications, while the ADS7844 is a general-purpose ADC, affecting intended use. |
| Operating temperature range | -40 °C to +85 °C | -40 °C to +85 °C | Matching temperature ranges ensure both work in the same environmental conditions. |
| Reference input | External reference supported | External reference supported | Both allow external voltage reference, enabling flexible full-scale range configuration. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADS7843E | ADS7844NB/1K |
|---|---|---|
| Part Status | Active | Active |
| Touchscreen | 3 Wire Capacitive | - |
| Resolution(Bits) | 12 b | - |
| Interface | Serial | - |
| Voltage Reference | External | - |
| Voltage - Supply | 2.7V ~ 5V | - |
| Supply Current | 280 µA | - |
| Operating Temperature | -40°C ~ 85°C (TA) | -40°C ~ 85°C |
| Mounting Type | Surface Mount | - |
| Number of Bits | - | 12 |
| Sampling Rate(Per Second) | - | 200k |
| Number of Inputs | - | 4, 8 |
| Input Type | - | Differential, Single Ended |
| Data Interface | - | SPI |
| Configuration | - | MUX-S/H-ADC |
| Ratio - S / H: ADC | - | 1:1 |
| Number of A/D Converters | - | 1 |
| Architecture | - | SAR |
| Reference Type | - | External |
| Voltage - Supply, Analog | - | 2.7V ~ 3.6V, 5V |
| Voltage - Supply, Digital | - | 2.7V ~ 3.6V, 5V |
Frequently asked questions
What are the key differences between the ADS7844NB/1K and the ADS7843E?
The ADS7844NB/1K is an 8-channel, 12-bit sampling analog-to-digital converter (ADC) with a serial interface, housed in a 20-pin SSOP package. The ADS7843E is a 4-wire resistive touch screen controller with a 12-bit ADC, housed in a 16-pin SSOP package. The ADS7844 is a general-purpose multiplexed ADC, while the ADS7843 is dedicated to touch screen digitizer applications with integrated pen-interrupt and touch-pressure measurement functions.
Can the ADS7844NB/1K and ADS7843E be used interchangeably in the same socket?
No. Although both are 12-bit successive-approximation ADCs from Texas Instruments in SSOP packages, they differ in pin count (20 vs 16), pin functions, channel count (8 vs 4), and control interface. The ADS7843E includes touch-screen-specific features such as pen-down detection and ratiometric reference switching that the ADS7844NB/1K does not provide. Direct substitution is not possible without redesigning the PCB and firmware.
What is the resolution and sampling architecture of each device?
Both devices use a 12-bit successive-approximation register (SAR) ADC architecture. The ADS7844NB/1K provides 12-bit resolution across 8 input channels with a throughput rate of up to 200 kSPS. The ADS7843E provides 12-bit resolution for 4-wire touch screen coordinate measurement, with a throughput rate of up to 125 kSPS.
What supply voltage ranges do the ADS7844NB/1K and ADS7843E support?
The ADS7844NB/1K operates from a single supply of 2.7 V to 5.25 V. The ADS7843E operates from a single supply of 2.2 V to 5.25 V. Both devices support low-power operation suitable for battery-powered and portable systems.
What communication interface do these devices use?
Both the ADS7844NB/1K and the ADS7843E use a serial SPI-compatible interface for communication with a host microcontroller. The ADS7844NB/1K uses a standard 4-wire serial interface (CS, DCLK, DIN, DOUT) for channel selection and data readout. The ADS7843E uses a similar serial interface but includes additional control for pen-interrupt and touch-pressure measurement modes.
Which device is appropriate for touch screen applications?
The ADS7843E is specifically designed as a 4-wire resistive touch screen controller, featuring pen-down detection, touch-pressure measurement, and ratiometric conversion optimized for touch digitizers. The ADS7844NB/1K is a general-purpose 8-channel ADC and does not include dedicated touch screen control features, so it is not the intended choice for touch screen digitizer designs.
What are the package and pin count differences between the two parts?
The ADS7844NB/1K is supplied in a 20-pin SSOP (Shrink Small Outline Package). The ADS7843E is supplied in a 16-pin SSOP. The different pin counts and pinouts mean the two devices are not footprint-compatible and require different PCB land patterns.
Do both devices support the same input channel configuration?
No. The ADS7844NB/1K provides 8 analog input channels that can be configured as single-ended or differential pairs, selectable via the serial interface. The ADS7843E provides 4 analog input channels dedicated to the X and Y coordinate plates and the touch-pressure measurement of a 4-wire resistive touch screen. The channel configurations serve different application purposes.