MAX17010ETL+T Maxim Integrated Products, MAX17010ETL+T Datasheet - Page 12

• Manufacturer Part Number: MAX17010ETL+T
• Description: IC LCD DISPLAY BIAS 40-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX17010ETL+T

• Applications: LCD Monitor, Notebook Display
• Current - Supply: 50µA
• Voltage - Supply: 1.8 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 40-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The regulator controls the output voltage, and the power
delivered to the output, by modulating the duty cycle (D)
of the internal power MOSFET in each switching cycle.
The duty cycle of the MOSFET is approximated by:
Figure 3 shows the block diagram of the step-up regu-
lator. An error amplifier compares the signal at FB to
1.235V and changes the COMP output. The voltage at
COMP determines the current trip point each time the
internal MOSFET turns on. As the load varies, the error
amplifier sources or sinks current to the COMP output
accordingly, to produce the inductor peak current ne-
cessary to service the load. To maintain stability at high
duty cycles, a slope-compensation signal is summed
with the current-sense signal.
On the rising edge of the internal clock, the controller
sets a flip-flop, turning on the n-channel MOSFET, and
applying the input voltage across the inductor. The cur-
rent through the inductor ramps up linearly, storing
energy in its magnetic field. Once the sum of the cur-
rent-feedback signal and the slope compensation
Internal-Switch Boost Regulator with Integrated
High-Voltage Level Shifter and Op Amp
Figure 3. Step-Up Regulator Block Diagram
12
______________________________________________________________________________________
D
≈
V
OSCILLATOR
MAIN
1.2MHz
V
MAIN
−
CLOCK
TO FAULT LOGIC
V
IN
COMPARATOR
SLOPE COMP
COMPARATOR
PWM
FAULT
CURRENT-LIMIT
COMPARATOR
+
-
+
-
-
+
LOGIC AND
DRIVER
1.0V
START
SOFT-
exceed the COMP voltage, the controller resets the flip-
flop and turns off the MOSFET. Since the inductor cur-
rent is continuous, a transverse potential develops
across the inductor that turns on the diode (D1). The
voltage across the inductor then becomes the diffe-
rence between the output voltage and the input volt-
age. This discharge condition forces the current
through the inductor to ramp back down, transferring
the energy stored in the magnetic field to the output
capacitor and the load. The MOSFET remains off for the
rest of the clock cycle.
The undervoltage lockout (UVLO) circuit compares the
input voltage at IN with the UVLO threshold (1.3V rising
and 1.2V falling) to ensure that the input voltage is high
enough for reliable operation. The 100mV (typ) hysteresis
prevents supply transients from causing a restart. Once
the input voltage exceeds the UVLO rising threshold,
startup begins. When the input voltage falls below the
UVLO falling threshold, the controller turns off the main
step-up regulator and the linear regulator outputs, dis-
ables the switch-control block, and the op amp outputs
are high impedance.
I
LIMIT
ERROR AMP
CURRENT
SENSE
+
-
1.235V
Undervoltage Lockout (UVLO)
LX
PGND
FB
COMP