HEF4521BT,653

HEF4521B 24-stage frequency divider and oscillator Rev. 7 — 30 March 2016 Product data sheet 1. General description The HEF4521B consists of a chain of 24 toggle flip-flops with an overriding asynchronous master reset input (MR), and an input circuit that allows three modes of operation. The single inverting stage (A2 to Y2) functions as: a crystal oscillator, an input buffer for an external oscillator or in combination with A1 as an RC oscillator. The crystal oscillator operates in Low-power mode when pins VSS1 and VDD1 are supplied via external resistors. Each flip-flop divides the frequency of the previous flip-flop by two, consequently the HEF4521B counts up to 224 = 16777216. The counting advances on the HIGH-to-LOW transition of the clock (A2). The outputs from each of the last seven stages (218 to 224) are available for additional flexibility. It operates over a recommended VDD power supply range of 3 V to 15 V referenced to VSS (usually ground). Unused inputs must be connected to VDD, VSS, or another input. 2. Features and benefits       Low power crystal oscillator operation Fully static operation 5 V, 10 V, and 15 V parametric ratings Standardized symmetrical output characteristics Specified from 40 C to +85 C Complies with JEDEC standard JESD 13-B 3. Ordering information Table 1. Ordering information All types operate from 40 C to +85 C. Type number HEF4521BT Package Name Description Version SO16 plastic small outline package; 16 leads; body width 3.9 mm SOT109-1 HEF4521B Nexperia 24-stage frequency divider and oscillator 4. Functional diagram