Global Mixed-mode Technology Inc.
Detailed Description
Shutdown Control
Digital logic of DIM provides an electrical ON/OFF
control of the power supply. Connecting this pin to
ground or to any voltage less than 0.2V with more than
10ms will completely turn off the regulator. In this state,
current drain from the input supply is less than 20µA
(Typ.), the internal reference, error amplifier, com-
parators, and biasing circuitry turn off.
Dimming Control
Digital logic of DIM provides LEDs brightness control
by applying a PWM signal on DIM pin. With this way,
the LEDs operate with either zero or full current. The
average LED current is proportional to the duty-cycle
of the PWM signal. Typical PWM frequency should be
between 100Hz to 1kHz.
DC Input voltage of DIM also provides LEDs bright-
ness control by applying a voltage signal between
0.3V to 1.23V on DIM pin. With this way, the LEDs
operate with full 100% brightness corresponds to V
DIM
equal or larger than 1.23V. When analog dimming is
required, the DC voltage range of V
DIM
should between
0.3V to 1.23V.
If dimming control is not required, one could just left
DIM floating to turn on LEDs.
G2605
Internal Thermal Shutdown
Thermal-overload protection limits total power dissipa-
tion in the G2605. When the junction temperature ex-
ceeds Tj=150°C, a thermal sensor activates the ther-
mal protection, which shutdowns the IC, allowing the
IC to cool. Once the device cools down by 30°C, IC
will automatically recover normal operation.
Thermal Protection of LED
G2605 will turn off switching if the voltage of TH pin
once lower than 0.082*VCC after VCC reaches 90% of
its value. If noise decoupling capacitor (C
TH
) is needed,
it’s value should be chosen by following equation:
(R
1
⏐
R
NTC
)
×
C
TH
< 2.5
×
10
-6
⏐
Once if G2605 enables TH protection, one should
power on G2605 or toggle DIM low for 10ms then high
again. Keep TH pin unconnected if Thermal protection
not needed.
Ver: 0.4
Oct 08, 2010
TEL: 886-3-5788833
http://www.gmt.com.tw
6
GMT [ GLOBAL MIXED-MODE TECHNOLOGY INC ]
