Ax

3 pF

30 pF

Conversion Phase: Switch Open

Track Phase: Switch Close

VDDA

SM72445

www.ti.com

SNVS795 – MARCH 2012

Figure 12. Forced Reset Condition

As seen in Figure 12, the initial value for output voltage and load current are 28V and 1A respectively. After the

reset pin is grounded both the output voltage and load current decreases immediately. MOSFET switching on the

buck-boost converter also stops immediately. VLOB indicates the low side boost output from the SM72295.

ANALOG INPUT

An equivalent circuit for one of the ADC input channels is shown in Figure 13. Diode D1 and D2 provide ESD

will cause the ESD diodes to conduct and result in erratic operation.

The capacitor C1 in Figure 13 has a typical value of 3 pF and is mainly the package pin capacitance. Resistor R1

is the on resistance of the multiplexer and track / hold switch; it is typically 500

Ω. Capacitor C2 is the ADC

sampling capacitor; it is typically 30 pF. The ADC will deliver best performance when driven by a low-impedance

source (less than 100

Ω). This is especially important when sampling dynamic signals. Also important when

sampling dynamic signals is a band-pass or low-pass filter which reduces harmonic and noise in the input. These

filters are often referred to as anti-aliasing filters.

Figure 13. Equivalent Input Circuit

DIGITAL INPUTS and OUTPUTS

output low voltage is 0.4V (max).

SCL and SDA

SCL is an input, and SDA is bidirectional with an open-drain output. SCL and SDA do not have internal pull-ups.

A “high” level will not be observed on this pin until pull-up current is provided by some external source, typically a

pull-up resistor. The choice of resistor value depends on many system factors such as load capacitance and

trace length. A typical value of pull-up resistor for SM72445 ranges from 2 k

Ω to 10 kΩ. For more information,

refer to the I2C Bus specification for selecting the pull-up resistor value. The SCL and SDA outputs can operate

while being pulled up to 5V and 3.3V.

Copyright © 2012, Texas Instruments Incorporated

Submit Documentation Feedback

11

Product Folder Links: SM72445