MAX8729EEI+T Maxim Integrated Products, MAX8729EEI+T Datasheet - Page 11

• Manufacturer Part Number: MAX8729EEI+T
• Description: Display Drivers Constant-Frequency H alf-Bridge CCFL Inve
• Manufacturer: Maxim Integrated Products

Specifications of MAX8729EEI+T

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PIN
18
19
20
21
22
23
24
25
26
27
28
LSYNC
NAME
PGND
ISEC
V
VFB
PS1
BST
IFB
GH
GL
LX
______________________________________________________________________________________
DD
Constant-Frequency, Half-Bridge CCFL
Lamp-Current Feedback Input. The IFB sense signal is internally full-wave rectified. The average
value of the rectified signal is regulated to 790mV (typ) by controlling the on-time of the high-side
MOSFET. An open-lamp fault is generated if the IFB is continuously below 790mV (typ) for a period
set by TFLT. See the Lamp-Out Protection and Setting the Fault-Delay Time sections for details.
Transformer Secondary-Voltage Feedback Input. When the peak voltage on VFB exceeds the 2.3V
(typ) overvoltage threshold, the controller turns on an internal 1.2mA current sink, discharging the
COMP capacitor. A capacitive voltage-divider between the high-voltage terminal of the CCFL tube
and GND determines the maximum lamp output voltage during startup and lamp-out fault. See the
Setting the Secondary Voltage Limit section for details.
Transformer Secondary-Current Feedback Input. When the peak voltage on ISEC exceeds the
internal overcurrent threshold, the controller turns on an internal 1.2mA current sink, discharging the
COMP capacitor. A current-sense resistor connected between the low-voltage end of the transformer
secondary and the ground determines the maximum secondary current during short-circuit fault. See
the Setting the Secondary Current Limit section for details.
DPWM Sync Input. DPWM frequency can be synchronized with an external signal on LSYNC. When
SEL is connected to V
a Schmitt trigger input.
Phase-Shift-Select Input. The PS1 and PS2 logic inputs select between four programmable phase
shifts (60°, 90°, 120°, and 180°) in master-slave operation. PS1 and PS2 should be in identical states
in each slave. See the Phase Shift in Daisy-Chain Operation (PS1, PS2) section for details.
Switching Node. LX is the return of the high-side gate driver. LX is also the input to the primary
current-limit and zero-crossing comparators. The controller senses the voltage across the high-side
MOSFET (IN - LX) and low-side MOSFET (LX - GND) to detect primary overcurrent condition and zero
crossing.
High-Side MOSFET Gate-Driver Output
High-Side Gate-Driver Supply Input. The MAX8729 includes an integrated boost diode. Connect a
0.1µF capacitor between LX and BST to complete the bootstrap circuit.
Power Ground. PGND is the return for the low-side gate driver.
Low-Side MOSFET Gate-Driver Output
Low-Side MOSFET Gate-Driver Supply Input
CC
, the duty cycle of the LSYNC signal determines the brightness. LSYNC has
FUNCTION
Inverter Controller
Pin Description (continued)
11