MAP3201SIH Просмотр технического описания (PDF) - MagnaChip Semiconductor

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MAP3201SIH

High current switch mode PWM LED Driver

MagnaChip Semiconductor 

Preliminary – Subject to change without notice

PROTECTION

The MAP3201 offers the features such as UVLO, Boost current limit,

Over Voltage Protection and Short Circuit Protection of LED (SCP).

OVP and SCP are operated in auto restart protection mode.

1. Under-Voltage Lock-Out (UVLO)

When VCC voltage reaches over 8V, UVLO starts operating which

enables Internal 5V Regulator, making all internal control circuits

including oscillator, gate driver and protection circuit ready for

operation and output pin of GATE, PWMO and COMP starts

operating depending on the input status of PWMI.

If VCC voltage drops below 7V during normal operation, UVLO

starts operating, shutting down Internal Control Circuit and stopping

operation of GATE, PWMO and COMP. It is followed by disabling of

internal 5V regulator, and shut off of all IC operation.

2. Pulse by Pulse Current Limit

It will operate Pulse by Pulse current limit as voltage ratio between

COMP Pin Voltage which is controlled by Gm Amp of Boost

converter and CS Pin voltage which will be caused by external

Boost FET.

3. Maximum Current Limit

Maximum current that is driven into Boost FET through CLIM Pin

voltage can be set up as in Figure 5

4. Over Voltage Protection (OVP)

The MAP3201 offers over voltage protection in order to protect

MOSFET of boost converter and external component connected to

Output pin when output voltage is in abnormal condition.

OVP Circuit monitors whether output voltage is stable level or not

If OVP Pin voltage reaches threshold condition (typical 3V), it can

shut off the switching of GATE and PWMO and then output voltage

is falling as much as the leakage current time. If the voltage of OVP

Pin reaches OVP falling threshold (typical 2.7V), IC releases

protection mode. In this time, protection releasing can be decided

as value of capacitor with the longer discharge between auto restart

time and the time of leakage current connected to output.

The over voltage protection can be decided in the following

equation.

- Protection voltage:

VO

=

3.0 *

RO 2

RO1 + RO2

- Protection release voltage:

VO

=

2.7 *

RO 2

RO1 + RO2

Figure 5 Current Sense and Maximum current limit

Figure 6 Over voltage protection circuit

The MAP3201 included LPF(low pass filter) of typical 200nS in OVP

circuit for better noise immunity, It may need a high noise margin

when Ro1 and Ro2 use high resistance value in order to minimize

Power loss.

In this case, it is recommended to add Capacitor.

VC, MAX: Maximum output voltage of Gm Amp

VOFF: Offset voltage of PWM comparator

VCS

= VC,MAX − 0.6V

5

− VOFF

VCS = VCLIM

The equation above can be used to set up Maximum boost current

when VCLIM is VCS.

5. Programmable Short Current Protection of LED

(SCP)

The MAP3201 offers protection circuit to prevent short current when

LED string is shorted

In Figure 7 when LED string is shorted, the voltage of FBN Pin can

be calculated in the following equation

VFBN = I LED ∗ RLED

OCT.15 2009. Version 0.3

MagnaChip Semiconductor Ltd.

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