MAX5033DASA Maxim Integrated Products, MAX5033DASA Datasheet - Page 9

• Manufacturer Part Number: MAX5033DASA
• Description: DC/DC Switching Converters 500mA 76V MAXPower Step-Down
• Manufacturer: Maxim Integrated Products

Specifications of MAX5033DASA

• Output Voltage: 13.2 V
• Output Current: 0.5 A
• Switching Frequency: 125 KHz
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-8
• Minimum Operating Temperature: - 40 C
• Number Of Outputs: 1
• Supply Current: 270 uA

The MAX5033 step-down DC-DC converter operates
from a 7.5V to 76V input voltage range. A unique volt-
age-mode control scheme with voltage feed-forward
and an internal switching DMOS FET provides high effi-
ciency over a wide input voltage range. This pulse-
width modulated converter operates at a fixed 125kHz
switching frequency. The device also features automat-
ic pulse-skipping mode to provide low quiescent cur-
rent and high efficiency at light loads. Under no load,
the MAX5033 consumes only 270µA, and in shutdown
mode, consumes only 10µA. The MAX5033 also fea-
tures undervoltage lockout, hiccup-mode output short-
circuit protection, and thermal shutdown.
Drive ON/OFF to ground to shut down the MAX5033.
Shutdown forces the internal power MOSFET off, turns
off all internal circuitry, and reduces the V
rent to 10µA (typ). The ON/OFF rising threshold is
1.69V (typ). Before any operation begins, the voltage at
ON/OFF must exceed 1.69V (typ). The ON/OFF input
has 100mV hysteresis.
Use the ON/OFF function to program the UVLO thresh-
old at the input. Connect a resistive voltage-divider
from V
shown in Figure 1. Calculate the threshold value by
using the following formula:
The minimum recommended V
and 13V for the output voltages of 3.3V, 5V, and 12V,
respectively. The recommended value for R2 is less
than 1MΩ.
If the external UVLO threshold-setting divider is not used,
an internal undervoltage-lockout feature monitors the
supply voltage at V
V
when V
time, use the resistive divider at ON/OFF.
Connect a flying bootstrap capacitor between LX and
BST to provide the gate-drive voltage to the high-side
n-channel DMOS switch. The capacitor is alternately
charged from the internally regulated output-voltage VD
and placed across the high-side DMOS driver. Use a
0.1µF, 16V ceramic capacitor located as close to the
device as possible.
IN
rises above 5.2V (typ). This feature can be used only
IN
IN
to GND with the center node to ON/OFF as
rise time is faster than 2ms. For slower V
Boost High-Side Gate Drive (BST)
V
UVLO TH
Undervoltage Lockout (UVLO)
_______________________________________________________________________________________
500mA, 76V, High-Efficiency, MAXPower
IN
(
and allows operation to start when
Detailed Description
)
=
⎛
⎝ ⎜
1
+
R
R
2
1
UVLO(TH)
⎞
⎠ ⎟
Shutdown Mode
×
1 85
.
V
IN
is 6.5V, 7.5V,
supply cur-
Step-Down DC-DC Converter
IN
rise
On startup, an internal low-side switch connects LX to
ground and charges the BST capacitor to VD. Once the
BST capacitor is charged, the internal low-side switch
is turned off and the BST capacitor voltage provides
the necessary enhancement voltage to turn on the
high-side switch.
The MAX5033 features integrated thermal-overload
protection. Thermal-overload protection limits total
power dissipation in the device, and protects the
device in the event of a fault condition. When the die
temperature exceeds +160°C, an internal thermal sen-
sor signals the shutdown logic, turning off the internal
power MOSFET and allowing the IC to cool. The ther-
mal sensor turns the internal power MOSFET back on
after the IC’s die temperature cools down to +140°C,
resulting in a pulsed output under continuous thermal-
overload conditions.
The MAX5033A/B/C have preset output voltages of 3.3V,
5.0V, and 12V, respectively. Connect FB to the preset
output voltage (see the Typical Operating Circuit ).
The MAX5033D offers an adjustable output voltage. Set
the output voltage with a resistive voltage-divider con-
nected from the circuit’s output to ground (Figure 1).
Connect the center node of the divider to FB. Choose
R4 less than 15kΩ, then calculate R3 as follows:
Figure 1. Adjustable Output Voltage
7.5V TO 76V
V
R1
R2
IN
47µF
ON/OFF
SGND
Applications Information
R
MAX5033D
V
3
IN
Thermal-Overload Protection
=
GND
Setting the Output Voltage
(
V
OUT
BST
VD
1 22
LX
FB
.
−
1 22
.
0.1µF
0.1µF
)
×
R
D1
50SQ100
4
220µH
41.2kΩ
13.3kΩ
R3
R4
5V, 0.5A
V
OUT
C
33µF
OUT
9