I

OUT

D * D

2

Upper:

Lower:

V

=2.5V×

(driver)

R1+R2

R1

V

=2.3V×

(driver)

R1+R2

R1

.

TPIC74101-Q1

www.ti.com

SLIS140

– OCTOBER 2011

PRINCIPLES OF OPERATION

Functional Principle

The TPIC74101-Q1 is a buck/boost switch-mode regulator that operates in a power-supply concept to ensure a

stable output voltage with input voltage excursions and specified load range.

The device provides an alarm indicator and reset output to interface with systems that require supervisory

function.

The switching regulator offers a clock modulator and a current-mode slew-rate control for the internal switching

transistor (Q1) to minimize EMI.

output.

Description of the Functional Terminals

Switch-Mode Input/Output Terminals (L1, L2)

The external inductor for the switch-mode regulator is connected between terminals L1 and L2. This inductor is

placed close to the terminals to minimize parasitic effects. For stability, an inductor with 20

μH to 100 μH should

be used.

minimize noise. A low-ESR aluminum or tantalum input capacitor is recommended. The relevant parameters for

the input capacitor are the voltage rating and RMS current rating. The voltage rating should be approximately 1.5

times the maximum applied voltage for an aluminum capacitor and 2 times for a tantalum capacitor. In buck

mode, the RMS current is

, where D is the duty cycle and its maximum RMS current value is

peak-to-peak ripple current in the inductor. To achieve this, ESR ceramic capacitors are used in parallel with the

aluminum or tantalum capacitors.

terminal can also be used as an output supply for the logic-level inputs for this device (SCR0, SCR1, ENABLE,

CLP, and 5Vg_ENABLE).

on the input supply. A maximum of 40 V may be applied to this terminal and the voltage at this terminal may

programmed to set the undervoltage detection threshold on this terminal (see the application schematic). The

input has a typical hysteresis of 200 mV with a typical upper limit threshold of 2.5 V and a typical lower limit

the high-impedance state.

(1)

Copyright

© 2011, Texas Instruments Incorporated

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