Datasheet

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 V
SS1
and V
DD1
are supplied via external resistors.
Each flip-flop divides the frequency of the previous flip-flop by two, consequently the
HEF4521B counts up to 2
24
= 16777216. The counting advances on the HIGH-to-LOW
transition of the clock (A2). The outputs from each of the last seven stages (2
18
to 2
24
) are
available for additional flexibility.
It operates over a recommended V
DD
power supply range of 3 V to 15 V referenced to V
SS
(usually ground). Unused inputs must be connected to V
DD
, V
SS
, 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
HEF4521B
24-stage frequency divider and oscillator
Rev. 6 — 21 November 2011 Product data sheet
Table 1. Ordering information
All types operate from
40
C to +85
C.
Type number Package
Name Description Version
HEF4521BP DIP16 plastic dual in-line package; 16-leads (300 mil) SOT38-4
HEF4521BT SO16 plastic small outline package; 16 leads; body width 3.9 mm SOT109-1

Summary of content (18 pages)