IL34118DWT from IKSEMICON, in a SOP-28-300mil. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	FO	output	Filter buffer output. Low-output-impedance (<50 Ω) output of the internal filter buffer used with external components to form a high-pass (60/120 Hz hum reject), low-pass, or band-pass filter in the receive path.
2	FI	input	Filter buffer input. High-impedance (>1.0 MΩ) input to the internal filter buffer; external RC network between FI and FO sets the filter response.
3	CD	input	Chip Disable. When asserted, powers down the entire circuit to conserve power (useful for long telephone loops where loop current is at a minimum).
4	VCC	power_in	Positive supply voltage, 3.0 V to 6.5 V. Typical line-powered operation draws ~5.0 mA.
5	HTO+	output	Hybrid amplifier 1 non-inverting output. Drives the coupling transformer through the balancing network Zbal; gain set by external resistors -RHF/RHI. Output current capability ≥5 mA (typ 8 mA limit).
6	HTO-	output	Hybrid amplifier 2 output (fixed internal gain of -1.0). Second of the two hybrid amplifiers used to form the two-to-four wire converter for the telephone line interface.
7	HTI	input	Hybrid amplifier inverting input. Bias current typically 30 nA out of the pin; open-loop gain ~80 dB, gain-bandwidth ~1.0 MHz.
8	TXO	output	Transmit attenuator output. Drives the transmit signal path toward the hybrid; complements RXO in half-duplex operation.
9	TXI	input	Transmit attenuator input. Nominal 10 kΩ input impedance; recommended input signal ≤350 mVrms (990 mVp-p) to prevent distortion.
10	MCO	output	Microphone amplifier output. Output impedance <10 Ω until current limit (~1.5 mA). Gain set by RMF/RMI external resistors between MCI and MCO.
11	MCI	input	Microphone amplifier inverting input. Non-inverting input is internally tied to VB. Input bias current typically 40 nA out of the pin.
12	MUT	input	Mute control input. When activated, reduces microphone amplifier gain to -39 dB by shorting the output to the inverting input (with RMI = 5.1 kΩ). Threshold ~1.5 V; must be kept between GND and VCC; tie to GND if unused.
13	VLC	input	Volume control input, sensed as a voltage with respect to VB. Adjusts the receive attenuator gain; -46 dB when VLC = VB and increasing toward +6.0 dB as VLC is reduced. Bias current typically 60 nA out of the pin.
14	CT	passive	Attenuator control timing capacitor. External CT (typ 5.0 μF) with RT (typ 120 kΩ) to VB sets the transmit/receive/idle switching time constants. Voltage at CT (relative to VB) directly monitors the circuit's mode.
15	VB	power_out	Internal analog reference/bias voltage (mid-supply). Serves as the AC ground reference for the attenuators, hybrid, microphone amplifier, and level detectors.
16	CPT	passive	Transmit background noise monitor capacitor. External capacitor stores a DC voltage representing the transmit-path noise level; slow rise time (external RC), fast decay. Should match CPR value within ±10%.
17	TLI2	input	Transmit level detector 2 input. Senses the microphone amplifier output signal for the transmit background noise / speech detection path.
18	TLO2	output	Transmit level detector 2 output. Charges an external capacitor (typ 2.0 μF) through a diode and 350 Ω limiting resistor to form a DC representation of the input AC signal level.
19	RLO2	output	Receive level detector 2 output. Charges an external capacitor (typ 2.0 μF) to represent the receive-side (speaker) signal level for the attenuator control block.
20	RLI2	input	Receive level detector 2 input. Senses the receive-side signal (typically the speaker amplifier output) for background noise / speech detection.
21	RXI	input	Receive attenuator input. Nominal 10 kΩ input impedance; recommended input signal ≤350 mVrms (990 mVp-p) to prevent distortion. Also feeds the dial tone detector comparator.
22	RXO	output	Receive attenuator output. Drives the receive signal path toward the speaker amplifier; complementary in gain to TXO.
23	TLI1	input	Transmit level detector 1 input. Senses the hybrid output (Tip/Ring side) signal level for the transmit control path.
24	TLO1	output	Transmit level detector 1 output. Charges an external capacitor (typ 2.0 μF) through a diode and 350 Ω limiting resistor to represent the TLI1 input AC signal level.
25	RLO1	output	Receive level detector 1 output. Feeds a comparator whose output goes to the attenuator control block; also feeds the receive background noise monitor.
26	RLI1	input	Receive level detector 1 input. Sees the same signal as at Tip/Ring for receive-side level detection.
27	CPR	passive	Receive background noise monitor capacitor. External capacitor stores a DC voltage representing receive-path noise level; charge/discharge sets response time to background noise variations (~4.7 s typical). Should match CPT within ±10%.
28	GND	power_in	Ground / negative supply return.

Key specifications

Parameter	Value
Manufacturer	IKSEMICON
Package	SOP-28-300mil
Category	Interface
Pins	28

Ordering variants

Same part, different packaging or reel option.

IL34118DWT
IL34118DWTN

CAD (KiCad official)

Symbol: IL34118DWT
Footprint: Package_SO:SOP-28_8.4x18.16mm_P1.27mm
3D model: SOP-28-300mil (KiCad packages3D, STEP)

Provenance

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

Datasheet: IKSEMICON datasheet (14 pp, sha256 b3cd47de9884e9d2, retrieved 2026-08-17, tier: lcsc)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF