MAX1817EUB Maxim Integrated Products, MAX1817EUB Datasheet - Page 8

• Manufacturer Part Number: MAX1817EUB
• Description: IC CONV DUAL DCDC STEP 10-UMAX
• Manufacturer: Maxim Integrated Products
• Type: Step-Up (Boost)r

Specifications of MAX1817EUB

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 2
• Voltage - Output: 3.3V or Adj Main, -28 ~ 28 V or Adj Secondary
• Current - Output: 125mA
• Frequency - Switching: 500kHz
• Voltage - Input: 1.5 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Power - Output: 444mW
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

the output voltage rises above the undervoltage thresh-
old, the control circuitry is enabled, allowing proper
regulation of the output voltage.
The MAX1817’s LCD step-up converter generates an
LCD bias voltage up to 28V by use of a 500mA, 1.1Ω
internal N-channel switching MOSFET (Figure 1). The
LCD step-up converter control circuitry is powered from
the main step-up converter output (OUT), so the voltage
at OUT must be above the OUT undervoltage lockout
voltage for the LCD step-up converter to operate.
Compact, High-Efficiency, Dual-Output
Step-Up DC-DC Converter
Figure 1. MAX1817 Simplified Functional Diagram
8
ON
ON
_______________________________________________________________________________________
V
IN
OFF
OFF
FB
ON
ONLCD
SHUTDOWN
SHUTDOWN
LOGIC
LOGIC
MAIN
LCD
MAX1817
75mV
LCD Step-Up Converter
DUAL-MODE FEEDBACK
UNDERVOLTAGE
LOCKOUT
AGND
1.25V
1.25V
AGND
AGND
COMPARATOR
COMPARATOR
BIAS
LCD
ERROR
ERROR
MAIN
LCD
STARTUP
During startup, the MAX1817 extends the minimum off-
time to 5µs for V
surge current. The LCD step-up converter features an
independent shutdown control, ONLCD.
The LCD step-up converter features a minimum-off-
time, current-limited control scheme. A pair of one-
shots that set a minimum off-time and a maximum on-
time governs the duty cycle. The switching frequency
can be up to 500kHz and depends upon the load, and
input and output voltages.
GND
CONTROL
CROSSING
DETECTOR
CONTROL
CURRENT
CURRENT
LOGIC
LOGIC
MAIN
ZERO-
LCD
LIMIT
LIMIT
MAIN
LCD
FBLCD
GND
GND
voltages <0.9V, limiting initial
FBLCD
LXLCD
OUT
LX
MAIN
LCD