MAX7384 Datasheet, PDF (6/9 Pages) Maxim Integrated Products – Silicon Oscillator with Low-Power Frequency Switching and Reset Output

Silicon Oscillator with Low-Power Frequency
Switching and Reset Output
Pin Description
PIN
NAME
FUNCTION
1
V_CC
Positive Supply Voltage. Bypass V_CC to GND with a 0.1µF capacitor.
2
V_L
Output Supply Voltage. Bypass V_L to GND with a 0.1µF capacitor. V_L must be connected to V_CC.
3
SPEED
Clock-Speed Select Input. Drive SPEED low to select the 32kHz fixed frequency. Drive SPEED high
to select factory-trimmed frequency.
4
RST
Reset Output. Open-drain or push-pull output. See the Ordering Information.
5
CLOCK Push-Pull Clock Output
6
GND
Ground
7
E.C.
Externally Connected. Connect to Vcc.
8
N.C.
No Connection. Not internally connected.
Detailed Description
The MAX7384 is a dual-speed clock generator with inte-
grated reset for microcontrollers (µCs) and UARTs in 3V,
3.3V, and 5V applications. The MAX7384 is a replace-
ment for crystal-oscillator modules, crystals, or ceramic
resonators and a system reset IC. The high-speed clock
frequency and reset threshold voltage are factory
trimmed to specific values (see Table 1). A variety of
popular standard frequencies are available. The low-
speed clock frequency is fixed at 32.768kHz; see Table
2. No external components are required for setting or
adjusting the frequency.
Oscillator
The push-pull clock output drives a load to within
400mV of either supply rail. The clock output remains
stable over the full operating voltage range and does
not generate short output cycles during either power-on
or changing of the frequency. A typical oscillating start-
up is shown in the Typical Operating Characteristics.
V_CC 2.7V TO 5.5V
V_L
MAX7384
SPEED _LOGIC
32kHz
(LF OSCILLATOR)
10MHz TO 16MHz
(HF OSCILLATOR)
GND
Figure 1. Functional Diagram
POR
MUX
RST
CLOCK
Clock-Speed Selection
Drive SPEED low to select slow clock speed (nominally
32.768kHz) or high to select full clock speed. SPEED can
be connected to V_CC or to GND to select fast or slow
clock speed, or connected to a logic output (such as a µP
GPIO port) used to change clock speed on the fly. If
SPEED is connected to a µP GPIO port, connect a pullup
or pulldown resistor to set the clock to the preferred
speed on power-up. SPEED input bias current is 2µA
(max), so a resistor value as high as 500kΩ can be used.
Applications Information
Interfacing to a Microcontroller
Clock Input
The MAX7384 clock output is a push-pull, CMOS, logic
output that directly drives a µP or µC clock input. There
are no impedance-matching issues when using the
MAX7384. Refer to the microcontroller data sheet for
clock input compatibility with external clock signals.
The MAX7384 requires no biasing components or load
capacitance. When using the MAX7384 to retrofit a
crystal oscillator, remove all biasing components from
the oscillator input.
Reset Output
The MAX7384 is available with three reset output stage
options: push-pull active low, push-pull active high, and
open-drain active low. RST is asserted when the moni-
tored input (V_CC) drops below the internal V_TH- threshold
and remains asserted for 120µs after the monitored input
exceeds the internal V_TH+ threshold. The open-drain
RST output requires an external pullup resistor.
Output Jitter
The MAX7384’s jitter performance is given in the
Electrical Characteristics table as a peak-to-peak value
obtained by observing the output of the MAX7384 for
6 _______________________________________________________________________________________