MAX17149ETE+ Maxim Integrated Products, MAX17149ETE+ Datasheet - Page 14

• Manufacturer Part Number: MAX17149ETE+
• Description: LED Drivers 6-String WLED Driver
• Manufacturer: Maxim Integrated Products

Specifications of MAX17149ETE+

• Operating Supply Voltage: 3 V to 26 V
• Maximum Supply Current: 4 mA
• Maximum Power Dissipation: 1176 mW
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: TQFN-16
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Low-Cost, 6-String WLED Drivers with
Quick-PWM Step-Up Converter
Figure 5 shows possible supply connection configura-
tions for the devices. The V
to GND with a minimum 1FF ceramic capacitor.
At startup, the devices perform an LED check by pull-
ing up each FB_ pin with a current source to determine
whether a string of LEDs are connected. If an FB_ pin
is not connected with LEDs, it is disabled. The process
takes approximately 1ms. Then the current sources are
turned on.
The devices can be placed into shutdown by pulling the
EN pin low; when in shutdown mode, the current con-
sumption is 5FA max. In the MAX17129, the V
drops to 0V with EN low.
To protect the step-up regulator when the load is open,
or the output voltage becomes excessive for any reason,
the devices feature a dedicated overvoltage feedback
input by monitoring output (OVP). There are two thresh-
olds for OVP and they provide careful protections. When
the OVP voltage exceeds the 40.8V (typ), an overvoltage
flag is set to enable the open-string detection. When the
OVP voltage exceeds 44.5V (typ), the internal power
MOSFET stops switching. This step-up regulator switch
is reenabled after the V
below the protection threshold. This overvoltage pro-
tection feature ensures the step-up regulator fail-safe
operation when the LED strings are disconnected from
the output.
Figure 5. Supply Configurations for the MAX17129/MAX17149
14
6V TO 26V
V
IN
OVP
Overvoltage Protection
CC
drops 1.5V (typ hysteresis)
pin should be bypassed
IN
V
CC
MAX17129
MAX17149
Shutdown
LX
CC
Startup
voltage
Maintaining uniform LED brightness and dimming capa-
bility is critical for backlight applications. The ICs are
equipped with a bank of six matched current sources.
These specialized current sources are accurate within
Q3% and match with each other within 2%. The LED
full-scale current is set through the ISET pin (10mA <
I
The minimum voltage drop across each current source
is 275mV (typ) when the LED current is 20mA. The low-
voltage drop helps reduce dissipation while maintaining
sufficient compliance to control the LED current within
the required tolerances.
The LED current sources can be disabled by connecting
the respective FB_ pin to GND before startup. When the
devices are enabled, the controller scans settings for
all FB_ pins. If a FB_ pin is not tied to GND, an internal
circuit pulls this pin high, and the controller enables the
corresponding current source to regulate the string cur-
rent. If the FB_ pin is tied to GND, the controller disables
the corresponding current regulator. The current regula-
tor cannot be disabled by connecting the respective FB_
pin to GND after the IC is enabled.
All FB_ pins in use are combined to extract a lowest FB_
voltage (LVC) (see Figure 2). LVC is fed into the step-up
regulator’s error amplifier and is used to set the output
voltage.
LED_FS
3.0V TO 5.5V
V
< 45mA).
S
IN
V
CC
MAX17129
MAX17149
LX
LED Current Sources