MAP3202SIRH Просмотр технического описания (PDF) - MagnaChip Semiconductor

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MAP3202SIRH

High Efficiency Switch Mode LED Driver

MagnaChip Semiconductor 

Confidential

Datasheet Version 1.1

GATE1

CH1 Boost Drain

GATE2

CH2 Boost Drain

GATE3

Figure 4 Peer - to -peer synchronization

(Fixed 100 KHz)

PROTECTION

The MAP3202 offers the features such as UVLO, Boost

current limit, Over Voltage Protection and Short Current

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. Maximum Boost Current Limit

MAP3202 has the internal current limit threshold voltage, 0.36V

(Typ.). If the sense voltage on CS pin exceeds 0.36V,

MAP3202 limits boost on duty every pulse.

MAP3202’s CS circuitry has the Leading edge blank time at

100nS (min.).

3. Over Voltage Protection (OVP)

The MAP3202 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 (3V Typ.), 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 (2.7V Typ.),

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:

Ro1+ Ro2

Vout = 3* Ro2

- Protection release voltage:

Vout

=

2.7 *

Ro1+ Ro2

Ro2

Vout

OVP

Auto Restart

Protection

LPF

+

10

-

3V / 2.7V

Ca

Figure 5 Over voltage protection circuit

The MAP3202 included LPF (low pass filter) of 200nS (Typ.) 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.

The total values of Ro1 and Ro2 need to be lower than 1Mohm.

In this case, it is recommended to add Capacitor.

4. Short Current Protection of LED (SCP)

The MAP3202 offers protection circuit to prevent short current

when LED string is shorted

In Figure 6 when LED string is shorted, the voltage of FBN Pin

can be calculated in the following equation

VFBN = I LED ∗ RLED

If the voltage of FBN pin exceeds the voltage of FBP X 2.5,

MAP3202 goes into SCP mode.

It is recommended which FBP max voltage 1.5V.

Figure 6 Short current protections

March 2012

Page 10

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