AS1330 datasheet(10/18 Pages) AMSCO

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AS1330

Datasheet - D e t a i l e d D e s c r i p t i o n

Current Sensing

A signal representing the internal NMOS-switch current is summed with the slope compensator. The summed signal is compared to the error

amplifier output to provide a peak current control command for the PWM. Peak switch current is limited to approximately 650mA independent of

VIN or VOUT.

Zero Current Comparator

The zero current comparator monitors the inductor current to the output and shuts off the PMOS synchronous rectifier once this current drops to

20mA (approx.). This prevents the inductor current from reversing polarity and results in improved converter efficiency at light loads.

Anti-Ringing Control

Anti-ringing control circuitry prevents high-frequency ringing on pin SW as the inductor current approaches zero. This is accomplished by

damping the resonant circuit formed by the inductor and the capacitance on pin SW (CSW).

Powersave Operation

In light load conditions, the integrated powersave feature removes power from all circuitry not required to monitor VOUT. When VOUT has

dropped approximately 1% from nominal, the device powers up and begins normal PWM operation.

C2 recharges, causing the AS1330 to re-enter powersave mode as long as the output load remains below the powersave threshold. The

frequency of this intermittent PWM is proportional to load current; i.e., as the load current drops further below the powersave threshold, the

AS1330 turns on less frequently. When the load current increases above the powersave threshold, the AS1330 will resume continuous,

seamless PWM operation.

Notes:

1. An optional capacitor (CFF) between pins VOUT and FB in some applications can reduce VOUTp-p ripple and input

quiescent current during powersave mode. Typical values for CFF range from 15 to 220pF.

2. In powersave mode the AS1330 draws only 30 A from the output capacitor(s), greatly improving converter efficiency.

Shutdown

When pin EN is low the AS1330 is switched off and <1 A current is drawn from the battery; when pin EN is high the device is switched on. If EN

is driven from a logic-level output, the logic high-level (on) should be referenced to VOUT to avoid intermittently switching the device on.

In shutdown the battery input is disconnected from the output.

Thermal Overload Protection

To prevent the AS1330 from short-term misuse and overload conditions the chip includes a thermal overload protection. To block the normal

operation mode the device is turning the PFET and the NFET off in PWM mode as soon as the junction temperature exceeds 150°C. To resume

the normal operation the temperature has to drop below 140°C.

Note:

Continuing operation in thermal overload conditions may damage the device and is considered bad practice.

AS1330 датащи(PDF) 10 Page - ams AG