AS3709 datasheet(9/74 Pages) AMSCO

9 / 74 page

ams Datasheet, Confidential: 2013-Aug [1-02]

AS3709 – 9

Detaile d Desc ri p t ion - P o w e r M a nagemen t Fu nc tions

Step Down DCDC Converter

The step-down converter is a high-efficiency fixed frequency

current mode regulator. By using low resistance internal PMOS

and NMOS switches, efficiency up to 95% can be achieved. The

fast switching frequency allows using small inductors, without

increasing the current ripple. The unique feedback and

regulation circuit guarantees optimum load and line regulation

over the whole output voltage range, up to an output current

of 1A, with an output capacitor of only 10μF. The implemented

current limitation protects the DCDC Converter and the coil

during overload condition.

Figure 8:

Step Down DC/DC Converter Block Diagram

Detailed Description -

Power Management Functions

Logic

IMIN

ILIMIT

250mA

1.2A

ISENSEP

ISENSEN

Zero

Comparator

PWM

Comparator

Overvoltage

Comparator

Ref + 8%

Ref - 5%

Slope

Compensation

Softstart

Ref = 0.6V

Skip

Sd_low_noise

Clk

Sd_lv

buck_v

FB_SD

VSS_SD

LX_SD

VOUT

VSUP

2.2uF

1uH

10uF

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