AAT1126 Просмотр технического описания (PDF) - Skyworks Solutions

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AAT1126

600mA, 1MHz Step-Down Converter

Skyworks Solutions 

DATA SHEET

AAT1126

600mA, 1MHz Step-Down Converter

VOUT = 1.8V

C1

10μF

GND

JP1

1

2

3

Enable

L1

4.7μH

R1

118K

R2

59K

C4

100pF

C3

n/a

1 GND

2 EN

3 LX

VIN 5

OUT 4

AAT1126

LX

VIN

C2

4.7μF

U1 AAT1126 SOT23-5

L1 CDRH3D16-4R7

C1 10μF 10V 0805 X5R

C2 4.7μF 10V 0805 X5R

Figure 1: Enhanced Transient Response Schematic.

Control Loop

The AAT1126 is a peak current mode step-down con-

verter. The current through the P-channel MOSFET (high

side) is sensed for current loop control, as well as short

circuit and overload protection. A fixed slope compensa-

tion signal is added to the sensed current to maintain

stability for duty cycles greater than 50%. The peak cur-

rent mode loop appears as a voltage-programmed cur-

rent source in parallel with the output capacitor.

The output of the voltage error amplifier programs the

current mode loop for the necessary peak switch current

to force a constant output voltage for all load and line

conditions. Internal loop compensation terminates the

transconductance voltage error amplifier output. For

fixed voltage versions, the error amplifier reference volt-

age is internally set to program the converter output

voltage. For the adjustable output, the error amplifier

reference is fixed at 0.6V.

Soft Start / Enable

Soft start limits the current surge seen at the input and

eliminates output voltage overshoot. When pulled low,

the enable input forces the AAT1126 into a low-power,

non-switching state. The total input current during shut-

down is less than 1μA. The AAT1126 provides turn-on

within 100μs (typical) of the enable input transition.

Current Limit and

Over-Temperature Protection

For overload conditions, the peak input current is limit-

ed. To minimize power dissipation and stresses under

current limit and short-circuit conditions, switching is

terminated after entering current limit for a series of

pulses. Switching is terminated for seven consecutive

clock cycles after a current limit has been sensed for a

series of four consecutive clock cycles.

Thermal protection completely disables switching when

internal dissipation becomes excessive. The junction

over-temperature threshold is 140°C with 15°C of hys-

teresis. Once an over-temperature or over-current fault

conditions is removed, the output voltage automatically

recovers.

Under-Voltage Lockout

Internal bias of all circuits is controlled via the VIN input.

Under-voltage lockout (UVLO) guarantees sufficient VIN

bias and proper operation of all internal circuitry prior to

activation.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

201976B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013

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