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LTC2870IUFD#TRPBF

Public Made by Adom

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Analog Devices RS-485 / RS-422 ICs, QFN-28(4x5). Pinout cross-checked by two models against the datasheet, KiCad symbol/footprint/3D.

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LTC2870IUFD#TRPBF

Analog Devices · RS-485 / RS-422 ICs · QFN-28(4x5)

LTC2870IUFD#TRPBF from Analog Devices, in a QFN-28(4x5). Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin Name Type Function
1 VEE power_out Generated negative supply (-6.3V) for the RS232 driver; tie all VEE pins together and connect a 1µF capacitor between VEE (sequentially after CAP) and GND.
2 RA output RS485 differential receiver output or RS232 receiver output 1, held Hi-Z when RXEN is high.
3 RB output RS232 receiver output 2, held Hi-Z when RXEN is high.
4 485/232 input Interface select: logic low enables RS232 mode and logic high enables RS485 mode; do not float.
5 RXEN input Receiver enable: logic high disables the RS232 and RS485 receivers leaving outputs Hi-Z, logic low enables them; do not float.
6 DXEN input Driver enable: logic low disables the RS232 and RS485 drivers leaving outputs Hi-Z, logic high enables them; do not float.
7 DY input RS485 driver input or RS232 driver input 1; do not float.
8 DZ input RS232 driver input 2; do not float.
9 FEN input Fast enable: logic high keeps the integrated DC/DC converter active regardless of driver, receiver and termination enables; logic low disables fast enable mode; do not float.
10 GND power_in Ground; tie all four GND pins together.
11 CAP passive Charge pump capacitor for the generated negative supply; connect a 220nF capacitor between CAP and SW.
12 VEE power_out Generated negative supply (-6.3V) for the RS232 driver; tie together with the other VEE pins and a 1µF capacitor to GND.
13 GND power_in Ground; tie all four GND pins together.
14 SW passive Switch pin for the boost converter; connect a 10µH inductor between SW and VCC.
15 VDD power_out Generated positive supply (+7V) for the RS232 driver; connect a 1µF capacitor between VDD and GND.
16 VCC power_in Input supply, 3V to 5.5V; tie all three VCC pins together and connect a 2.2µF or larger capacitor between VCC (adjacent to VDD) and GND.
17 Z bidirectional RS485 negative driver output or RS232 driver output 2 (LTC2870); also the RS485 negative receiver input in half-duplex mode.
18 GND power_in Ground; tie all four GND pins together.
19 Y bidirectional RS485 positive driver output or RS232 driver output 1 (LTC2870); also the RS485 positive receiver input in half-duplex mode.
20 VCC power_in Input supply, 3V to 5.5V; tie together with the other VCC pins and the 2.2µF or larger VCC-to-GND capacitor.
21 B input RS485 negative receiver input in full-duplex mode, or RS232 receiver input 2 (LTC2870).
22 A input RS485 positive receiver input in full-duplex mode, or RS232 receiver input 1 (LTC2870).
23 GND power_in Ground; tie all four GND pins together.
24 VCC power_in Input supply, 3V to 5.5V; tie together with the other VCC pins and the 2.2µF or larger VCC-to-GND capacitor.
25 VL power_in Logic supply, 1.7V to 5.5V, for receiver outputs, driver inputs and control inputs; keep VL ≤ VCC for proper operation.
26 LB input Loopback enable: logic high routes driver input logic levels to the receiver outputs; do not float.
27 H/F input RS485 half-duplex select: logic low selects full-duplex and logic high selects half-duplex operation; do not float.
28 TE485 input RS485 termination enable: logic high enables 120Ω resistors between A-B and Y-Z; logic low leaves them open; do not float.
29 VEE power_out Exposed pad, electrically VEE (generated negative supply); must be soldered to the PCB.

Key specifications

Parameter Value
Manufacturer Analog Devices
Package QFN-28(4x5)
Category Interface
Pins 29

Electrical characteristics

Limits as printed in the datasheet (page.json metadata.characteristics carries them as data).

Parameter Symbol Min Typ Max Unit Conditions Page
VCC Supply Voltage Operating Range VCC 3 5.5 V 4
VL Logic Supply Voltage Operating Range VL 1.7 V VL ≤ VCC 4
VCC Supply Current in Shutdown Mode (LTC2870) VCC 8 60 µA RXEN = VL, DXEN = TE485 = FEN = 0V, (LTC2870) 4
VL Supply Current in Transceiver Mode (Outputs Unloaded) VL 0 5 µA 4
/VOD/ Differential Output Voltage /VOD/ 1.5 6 V RL = ∞, VCC = 3V (Figure 1) 4
/VOD/ Differential Output Voltage /VOD/ 1.5 V RL = 27Ω, VCC = 3V (Figure 1) 4
/VOD/ Differential Output Voltage /VOD/ 2 V RL = 50Ω, VCC = 3.13V (Figure 1) 4
Difference in Magnitude of Differential Output Voltage for Complementary Output States ∆/VOD/ 0.2 V RL = 27Ω, VCC = 3V (Figure 1) 4
Common Mode Output Voltage VOC 3 V RL = 27Ω or 50Ω (Figure 1) 4
Difference in Magnitude of Common Mode Output Voltage for Complementary Output States ∆/VOC/ 0.2 V RL = 27Ω or 50Ω (Figure 1) 4
Three-State (High Impedance) Output Current IOZD485 -100 125 µA VOUT = 12V or -7V, VCC = 0V or 3.3V (Figure 2) 4
Maximum Short-Circuit Current IOSD485 -250 250 mA -7V ≤ VOUT ≤ 12V (Figure 2) 4
Input Current IIN485 -100 125 µA VIN = 12V or -7V, VCC = 0V or 3.3V (Figure 3) (Note 5) 4
Input Resistance RIN485 96 125 kΩ VIN = 12V or -7V, VCC = 0V or 3.3V (Figure 3) (Note 5) 4
Differential Input Signal Threshold Voltage (A-B) -200 200 mV -7V ≤ (A or B) ≤ 12V (Note 5) 4
Differential Input Failsafe Threshold Voltage -200 -70 0 mV -7V ≤ (A or B) ≤ 12V, (A-B) Rising (Note 5) 4
VOL Output Low Voltage VOL 0.4 V Output Low, I(RA, RO) = 3mA (Sinking), 3V ≤ VL ≤ 5.5V 4
Three-State (High Impedance) Output Current -5 0 5 µA 0V ≤ (RA, RO) ≤VL, VL = 5.5V 4
Short-Circuit Output Current -125 125 mA 0V ≤ (RA, RO) ≤VL, VL = 5.5V 4
Terminating Resistor RTERM 108 120 156 Ω TE485 = VL, A, B = 2V, B = -7V, 0V, 10V (Figure 8) (Note 5) 5
Output Low Voltage (RS232 driver) VOLD -5 -5.7 -7.5 V RL = 3kΩ; VEE ≤ -5.9V 5
Output High Voltage (RS232 driver) VOHD 5 6.2 7.5 V RL = 3kΩ; VDD ≥ 6.5V 5
Three-State (High Impedance) Output Current -156 156 µA Y or Z (LTC2870) = ±15V, RS232 Receiver Enabled 5
Output Short-Circuit Current (RS232 driver) -35 90 mA Driver Output = 0V 5
Input Threshold Voltage (RS232 receiver) 0.6 1.5 2.5 V 5
Input Hysteresis (RS232 receiver) 0.1 0.4 1 V 5
Output Low Voltage (RS232 receiver) 0.4 V I(RA, RB, ROUT1, ROUT2) = 1mA (Sinking) 1.7V ≤ VL ≤ 5.5V 5
Input Resistance (RS232 receiver) 3 5 7 kΩ -15V ≤ (A, B, RIN1, RIN2) ≤ 15V, RS232 Receiver Enabled 5
Three-State (High Impedance) Output Current (RS232 receiver) -5 0 5 µA 0V ≤ (RA, RB, ROUT1, ROUT2) ≤ VL 5
Output Short-Circuit Current (RS232 receiver) -25 50 mA VL = 5.5V, 0V ≤ (RA, RB, ROUT1, ROUT2) ≤ VL 5
Input Current (logic inputs) -5 0 5 µA 5
VDD/VEE Supply Rise Time 0.2 2 ms FEN = , (Notes 3 and 4) 6
ESD HBM - LTC2870 Interface Pins (A, B, Y, Z) -26 26 kV Human Body Model to GND or VCC, Powered or Unpowered (Note 7) 5
ESD HBM - All Other Pins -4 4 kV Human Body Model (Note 7) 5
Maximum Data Rate (RS485) 20 Mbps (Note 3) 6
Driver Propagation Delay tPLHD485, tPHLD485 20 70 ns RDIFF = 54Ω, CL = 100pF (Figure 4) 6
Driver Skew (Y to Z) tSKEWD485 1 6 ns RDIFF = 54Ω, CL = 100pF (Figure 4) 6
Receiver Input to Output tPLHR485, tPHLR485 65 85 ns CL = 15pF, VCM = 1.5V, /A, B/ = 1.5V (Figure 6) (Note 5) 6
Differential Receiver Skew tSKEWR485 1 6 ns CL = 15pF (Figure 6) 6
Maximum Data Rate (RS232, CL = 2500pF) 100 kbps RL = 3kΩ, CL = 2500pF (Note 3) 6
Maximum Data Rate (RS232, CL = 500pF) 500 kbps RL = 3kΩ, CL = 500pF (Note 3) 6
Driver Slew Rate 4 V/µs RL = 3kΩ, CL = 2500pF (Figure 9) 6
Driver Slew Rate 30 V/µs RL = 3kΩ, CL = 50pF (Figure 9) 6
Driver Propagation Delay (RS232) tPHLD232, tPLHD232 1 2 µs RL = 3kΩ, CL = 50pF (Figure 9) 6
Receiver Propagation Delay (RS232) tPHLR232, tPLHR232 60 200 ns CL = 150pF (Figure 11) 6
Receiver Rise or Fall Time (RS232) tRR232, tFR232 60 200 ns CL = 150pF (Figure 11) 6
Input Supplies VCC, VL (absolute maximum) VCC, VL -0.3 7 V 2
Generated Supply VDD (absolute maximum) VDD 7.5 V 2
Generated Supply VEE (absolute maximum) VEE -7.5 V 2
Switch Pin SW (absolute maximum) SW -0.3 V Upper limit printed as (VDD + 0.3V) 2
Interface Pins (absolute maximum) A, B, Y, Z, RIN1, RIN2, DOUT1, DOUT2 -15 15 V 2
Logic Input Pins (absolute maximum) DI, DZ, DY, RXEN, DXEN, LB, H/F, TE485, RX485, DX485, RX232, DX232, DIN1, DIN2, 485/232, CH2 -0.3 7 V 2
Logic Output Pins (absolute maximum) FEN, RA, RB, RO, ROUT1, ROUT2 -0.3 V Upper limit printed as (VL + 0.3V) 2
Differential Enabled Terminator Voltage (A-B or Y-Z) -6 6 V 2
Operating Temperature (LTC2870I) -40 85 °C LTC2870I 2
Storage Temperature Range -65 125 °C 2
Maximum Junction Temperature TJMAX 150 °C 2
Thermal Resistance, Junction to Ambient (28-lead QFN UFD package) θJA 43 °C/W UFD package (28-lead 4mm × 5mm QFN) 2

CAD (KiCad official)

  • Symbol: LTC2870IUFD#TRPBF
  • Footprint: Package_DFN_QFN:QFN-28-1EP_4x5mm_P0.5mm_EP2.65x3.65mm
  • 3D model: QFN-28(4x5) (KiCad packages3D, STEP)
  • 3D model files: ltc2870iufd-trpbf-etched.step / ltc2870iufd-trpbf-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); ltc2870iufd-trpbf.step / ltc2870iufd-trpbf.glb are the bare package body.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

  • Datasheet: Analog Devices datasheet (42 pp, sha256 bed34b4f97b6f3f8, retrieved 2026-10-21, tier: lcsc)
  • Extractor: parts-factory 2.0.0 / extract_pins 0.3, primary claude-haiku-5-5 (text), consensus claude-sonnet-5-5 (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
  • CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF