AAT2513 datasheet(11/22 Pages) ANALOGICTECH

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AAT2513

Dual 600mA Step-Down

Converter with Synchronization

2513.2007.04.1.1

Figure 1: AAT2513 Typical Schematic.

2.2uH

4.7μF

1.8V

118k

2.2μH

2.5V

59.0k

10μF

187k

FB1

EN1

LX1

PGND2

LX2

PGND1

AGND

VIN1

VIN2

FB2

EN2

VCC

MODE/SYNC

N/C

AAT2513

4.7μF

Low Supply UVLO

Under-voltage lockout (UVLO) guarantees suffi-

cient V

IN bias and proper operation of all internal

circuitry prior to activation.

Fault Protection

For overload conditions, the peak inductor current

is limited. Thermal protection disables the convert-

er when the internal dissipation or ambient temper-

ature becomes excessive. The over-temperature

threshold for the junction temperature is 140°C with

15°C of hysteresis.

PWM/LL Operation

For fixed frequency, with minimum ripple under

light load conditions, the MODE/SYNC pin should

be tied to a logic high. For more efficient operation

under light load conditions the MODE/SYNC pin

should be tied to a logic low level.

Clock Phase and Frequency

A logic high on the PS pin while in PWM mode

forces both converters to operate 180° out of phase

thus reducing the input ripple by roughly half. A

logic low on the PS pin synchronizes both convert-

ers in phase.

Applications Information

Inductor Selection

The step down converter uses peak current mode

control with slope compensation to maintain stability

for duty cycles greater than 50%. The output induc-

tor value must be selected so the inductor current

down slope meets the internal slope compensation

requirements. The internal slope compensation for

the adjustable and low voltage fixed versions of the

AAT2513 is 0.6A/µsec. This equates to a slope com-

pensation that is 75% of the inductor current down

slope for a 1.8V output and 2.2µH inductor.

In this case a standard 3.3µH value is selected.

0.75

⋅ V

L =

≈ 1.2

⋅ V

= 1.2

2.5V = 3.1µH

0.75V

⋅ V

0.6

µs

0.75

⋅ V

m =

= 0.6

0.75

⋅ 1.8V

2.2µH

µsec

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