MAX1796EUA Maxim Integrated Products, MAX1796EUA Datasheet - Page 9

• Manufacturer Part Number: MAX1796EUA
• Description: IC CONV DCDC W/SHUTDWN 8-UMAX
• Manufacturer: Maxim Integrated Products
• Type: Step-Up (Boost)r

Specifications of MAX1796EUA

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 3.3V, 5V, Adj
• Current - Output: 300mA
• Frequency - Switching: 500kHz
• Voltage - Input: 1 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Power - Output: 330mW
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

The internal synchronous rectifier eliminates the need
for an external Schottky diode, reducing cost and
board space. During the cycle off-time, the P-channel
MOSFET turns on and shunts the MOSFET body diode.
As a result, the synchronous rectifier significantly
improves efficiency without the addition of an external
component. Conversion efficiency can be as high
as 95%, as shown in the Typical Operating Char-
acteristics.
The device enters shutdown when V
reducing supply current to less than 2µA. During shut-
down, the synchronous rectifier disconnects the output
from the input, eliminating the DC conduction path that
normally exists with traditional boost converters in shut-
down mode. In shutdown, OUT becomes a high-imped-
Figure 2. Functional Diagram
Low Supply Current, Step-Up DC-DC Converters
OUT
BATT
R2
R3
R1
1M
SHDN
LBO
LBI
FB
START
+
_
_______________________________________________________________________________________
REFERENCE
FB SELECT
0.85V
+
_
Synchronous Rectification
TON MAX
TIMER BLOCK
TOFF
MAX
+
_
ERROR
AMPLIFIER
MAX1795
MAX1796
MAX1797
SHDN
Shutdown
Q
is high,
S
R
S
S
R
R
Q
Q
CURRENT-LIMIT
AMPLIFIER
ance node. The LBI/LBO comparator remains active in
shutdown.
As shown in Figure 1, the MAX1795/MAX1796/MAX1797
may be automatically shut down when the input voltage
drops below a preset threshold by connecting LBO to
SHDN (see Low-Battery Detection section).
The MAX1795/MAX1796/MAX1797 each contain an
internal damping switch to minimize ringing at LX. The
damping switch connects a resistor across the inductor
when the inductor’s energy is depleted (Figure 3).
Normally, when the energy in the inductor is insufficient
to supply current to the output, the capacitance and
inductance at LX form a resonant circuit that causes
ringing. The ringing continues until the energy is dissi-
pated through the series resistance of the inductor.
The damping switch supplies a path to quickly dissi-
CROSSING
AMPLIFIER
ZERO-
with True-Shutdown
+
+
_
-
+
_
CONTROL
BATT/Damping Switch
DIODE
BODY
BATT
GND
OUT
LX
22µH
47µF
OUT
BATT
47µF
9