MAX1678EUA Maxim Integrated Products, MAX1678EUA Datasheet - Page 7

• Manufacturer Part Number: MAX1678EUA
• Description: DC/DC Switching Converters
• Manufacturer: Maxim Integrated Products

Specifications of MAX1678EUA

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Figure 1. Functional Diagram
The MAX1678 consists of an internal 1Ω, N-channel
MOSFET power switch, a built-in synchronous rectifier
that acts as the catch diode, a reference, PFM control
circuitry, and an inductor damping switch (Figure 1).
The device is optimized for applications that are pow-
ered by 1 to 3-cell alkaline, NiMH, or NiCd batteries, or
a 1-cell lithium battery such as pagers, remote controls,
and battery-powered instruments. They are designed to
meet the specific demands of the operating states
characteristic of such systems:
1) Primary battery is good and load is active: In this
state the load draws tens of milliamperes and the
MAX1678 typically offers 80% to 90% efficiency.
SHDN
BATT
PFO
PFI
0.5REF
High-Efficiency, Step-Up DC-DC Converter
1.23V REF
_______________________________________________________________________________________
RFRDY
Detailed Description
REF
0.5REF
START-UP COMPARATOR
MAX1678
OUT
DAMPING
SWITCH
1.7V
1-Cell to 2-Cell, Low-Noise,
EN
DAMP
2) Primary battery is good and load is sleeping: In this
3) Primary battery is dead and DC-DC converter is
4) Primary and backup battery dead: The DC-DC con-
t
ON
state the load draws hundreds of microamperes and
the DC-DC converter IC draws very low quiescent
current. Many applications maintain the load in this
state most of the time.
shut down: In this state the load is sleeping or sup-
plied by the backup battery, and the MAX1678
draws 0.1µA current from the OUT pin.
verter can restart from this condition.
= K/V
CONTROL LOGIC
TON
OSCILLATOR
BATT
START-UP
BACKUP t
TIMER
REF
TOFF
OFF
NDRV
PDRV
ZERO-CROSSING
DETECTION
P
N
OUT
GND
LX
FB
7