MAX1760HETB+T Maxim Integrated Products, MAX1760HETB+T Datasheet - Page 8

• Manufacturer Part Number: MAX1760HETB+T
• Description: IC DC-DC CONV STP UP 10-TDFN
• Manufacturer: Maxim Integrated Products
• Type: Step-Up (Boost)r

Specifications of MAX1760HETB+T

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 3.3V, 2.5 ~ 5.5 V
• Current - Output: 800mA
• Frequency - Switching: 1MHz
• Voltage - Input: 0.7 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-TDFN Exposed Pad
• Power - Output: 1.48W
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

output filter capacitor and the load. As the energy
stored in the inductor is depleted, the current ramps
down and the synchronous rectifier turns off. At light
loads, the device operates at fixed frequency or only as
needed to maintain regulation, depending on the
CLK/SEL setting (Table 2).
Pulling CLK/SEL low selects the MAX1760’s normal
operating mode. In this mode, the device operates in
PWM when driving medium-to-heavy loads, and auto-
matically switches to PFM if the load requires less
power. PFM operation allows higher efficiency than
PWM under light-load conditions.
When CLK/SEL is high, the MAX1760 operates in a low-
noise PWM-only mode. During forced-PWM operation,
the MAX1760 switches at a constant frequency (1MHz)
and modulates the MOSFET switch pulse width to con-
trol the power transferred per cycle to regulate the out-
put voltage. Switching harmonics generated by
fixed-frequency operation are consistent and easily fil-
tered. See the Noise Spectrum plot in the Typical
Operating Characteristics.
The MAX1760 can be synchronized in PWM mode to an
external frequency of 500kHz to 1.2MHz by applying an
external clock signal to CLK/SEL. This allows interfer-
ence to be minimized in wireless applications. The syn-
chronous rectifier is active during synchronized-PWM
operation.
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
Table 1. Typical Available Output Current
Table 2. Selecting the Operating Mode
8
NUMBER OF NiCd/NiMH
_______________________________________________________________________________________
500kHz to 1.2MHz
External clock
CLK/SEL
CELLS
0
1
1
2
3
Synchronized-PWM Operation
Forced-PWM Operation
Synchronized PWM
Normal operation
Forced PWM
Normal Operation
MODE
INPUT VOLTAGE
(V)
1.2
2.4
2.4
3.6
High efficiency at all loads. Fixed frequency at all but light loads.
Low noise, fixed frequency at all loads.
Low noise, fixed frequency at all loads.
The MAX1760 features an internal, P-channel synchro-
nous rectifier to enhance efficiency. Synchronous recti-
fication provides 5% improved efficiency over similar
nonsynchronous boost regulators. In PWM mode, the
synchronous rectifier is turned on during the second
half of each switching cycle. In low-power mode, an
internal comparator turns on the synchronous rectifier
when the voltage at LX exceeds the boost regulator
output, and turns it off when the inductor current drops
below 60mA. When setting output voltages greater than
4V, an external 0.5A Schottky diode must be connected
in parallel with the on-chip synchronous rectifier.
The MAX1760 uses a CMOS, low-voltage startup oscil-
lator for a 1.1V guaranteed minimum startup input volt-
age. At startup, the low-voltage oscillator switches the
N-channel MOSFET until the output voltage reaches
2.15V. Above this level, the normal boost-converter
feedback and control circuitry take over. Once the
device is in regulation, it can operate down to 0.7V
input since internal power for the IC is bootstrapped
from the output through OUT. Do not apply full load
until the output exceeds 2.3V.
The MAX1760 has a shutdown mode that reduces qui-
escent current to 0.1µA. During shutdown (ON = high
on MAX1760, ON = low on MAX1760H), the reference
and all feedback and control circuitry are off. During
shutdown, the output voltage is one diode drop below
the input voltage.
OUTPUT VOLTAGE
3.3
3.3
5.0
5.0
(V)
Low-Voltage Startup Oscillator
FEATURES
Synchronous Rectifier
OUTPUT CURRENT
(mA)
350
800
500
750
Shutdown