Asahi Kasei Microdevices/AKM AK1573B

Overview

AK1573B from AsahiKASEI is an Integer-N frequency synthesizer with integrated VCO, designed as a local oscillator in RF signal chains. It operates over 1728–2600 MHz (VCO), supports programmable output division (1/2/4/8/16/32/64), delivers −12 to +6 dBm output power, consumes 44 mA at 1.8 GHz, and features analog/digital lock detect for cellular base station transceivers.

For engineers reviewing the AK1573B datasheet, AK1573B pinout, AK1573B application, or AK1573B equivalent, this page provides verified specifications, validated 24-pin QFN package mapping, confirmed VCO tuning sensitivity (≈0.02 MHz/V), real-world phase noise performance (−86 dBc/Hz @10 kHz offset), and functional alternatives for wireless infrastructure PLL design.

Technical Context

The AK1573B implements a dual-modulus prescaler (P/P+1) architecture with 13-bit swallow counter and 12-bit programmable counter, enabling precise integer-N frequency synthesis. Its integrated VCO eliminates external resonator requirements while supporting fast lock-up mode via dedicated register-controlled timing.

It interfaces via a 3-wire serial bus (CLK/DATA/LE) with Schmitt-trigger inputs, operates from 2.7–3.3 V, and requires an external loop filter to close the PLL. The charge pump current is adjustable via BIAS resistor (27 kΩ typical) and register CP1[2:0], with separate settings for normal and fast-lock operation.

Key Specifications

Pinout & Package

AK1573B is housed in a 24-pin QFN package (4.0 mm × 4.0 mm, 0.5 mm pitch) with exposed thermal pad connected to ground. Pin functions are validated per official AsahiKASEI pin configuration diagram (Figure 2).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar frequency synthesizer applications.

Compared with LMX2594RHBR and ADF4355BCPZ, AK1573B offers lower current draw (44 mA), superior close-in phase noise (−86 dBc/Hz @10 kHz), and simpler 3-wire interface-making it optimal for cost- and power-sensitive 2.6 GHz infrastructure LO generation where integer-N resolution suffices.

Availability

AK1573B is available at Aetrix Electronics and suitable for cellular base station transceivers, public safety radio systems, and fixed wireless access units requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for AK1573B includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

AsahiKASEI is a Japanese semiconductor manufacturer specializing in high-performance analog and mixed-signal ICs for communications, industrial, and automotive markets.

The AK1573 series targets wireless infrastructure applications, delivering compact, low-noise frequency synthesis with integrated VCO to reduce design complexity and improve RF system reliability.

FAQ

What is the VCO frequency range supported by AK1573B?

The AK1573B supports a VCO frequency range of 1728–2600 MHz, covering key cellular bands including LTE Band 1 (2100 MHz), Band 3 (1800 MHz), Band 7 (2600 MHz), and TDD-LTE Band 38/41. This range is confirmed in the official AsahiKASEI datasheet section "Frequency Coverage Options" and validated in Figure 17's VCO phase noise plots.

How does AK1573B achieve fast lock-up, and what register controls it?

The AK1573B achieves fast lock-up via dedicated charge pump current (CP2[2:0]) and timer (FAST[3:0]) registers. Enabling FASTEN bit in Address 0x04 activates the mode, while FAST[3:0] sets the duration (3–63 cycles). This reduces lock time significantly compared to standard operation, as documented in Section 13.3 "Fast Lock-up mode" of the datasheet.

What is the function of the BIAS pin on AK1573B, and what resistance value is recommended?

The BIAS pin on AK1573B sets the baseline charge pump current using an external resistor. A 27 kΩ resistor is specified for typical operation, yielding 44 mA total supply current at 1.8 GHz. The relationship is defined as Icp_min = 9.45 µA / BIAS resistance, with CP1[2:0] bits scaling current in discrete steps, per Section 10.3 and Register Map Address 0x02.

Can AK1573B operate with a 100 MHz reference input, and what is the maximum allowable PFD frequency?

Yes, AK1573B supports a 100 MHz reference input, as demonstrated in Figures 16–17 and Table 10.3. The maximum PFD frequency is 104 MHz, enforced by the R-counter (14-bit) and prescaler (P/P+1) configuration. For 100 MHz REFIN, R=100 yields 1 MHz PFD frequency, well within specification and used in all typical-characteristics graphs.

Does AK1573B include an integrated loop filter, or is an external filter required?

AK1573B requires an external loop filter; it does not integrate one. The device outputs charge pump current (CP pin) to drive a passive RC network (e.g., C1=33 pF, C2=1500 pF, R2=10 kΩ as shown in Figure 5). This external topology allows designers to optimize loop bandwidth and stability for specific application requirements like settling time or phase margin.