Rainbow Electronics MAX1678 - Manual (Page 6)

MAX1678
1-Cell to 2-Cell, Low-Noise,
High-Efficiency, Step-Up DC-DC Converter
6 _______________________________________________________________________________________
A
B
C
SWITCHING WAVEFORM
MAX1678-19
V OUT = 3.3V, V BATT = 1.2V, I LOAD = 10mA, C OUT = 10 µ F,
L1 = SUMIDA CD43-470
A: LX, 2V/div B: V
OUT , 50mV/div AC COUPLED
C: INDUCTOR CURRENT, 100mA/div
5 µ s/div
Typical Operating Characteristics (continued)
(Circuit of Figure 7 (Fixed Mode, 3.3V) or Figure 8 (Adjustable Mode), T A = +25°C, unless otherwise noted.)
Pin Description
PIN
Battery-Power Input BATT 1
FUNCTION NAME
A
B
C
LOAD-TRANSIENT RESPONSE
MAX1678-20
V OUT = 3.3V, V BATT = 1.2V, C OUT = 10 µ F,
L1 = SUMIDA CD43-470,
A: V
OUT
, 50mV/div, AC COUPLED B: INDUCTOR CURRENT,
C: LOAD, 2mA to 12mA 100mA/div
100 µ s/div
A
B
LINE-TRANSIENT RESPONSE
MAX1678-21
V OUT = 3.3V, V BATT = 1.2V, I LOAD = 10mA, C OUT = 10 µ F,
L1 = SUMIDA CD43-470
A: V
OUT
, 50mV/div, AC COUPLED B: V
IN
, 1V/div, 1.2V to 2.2V
200 µ s/div
A
B
C
POWER-UP RESPONSE
MAX1678-22
V OUT = 3.3V, V BATT = 1.2V, I LOAD = 10mA, C OUT = 10 µ F,
L1 = SUMIDA CD43-470
A: V
OUT , 1V/div B: INDUCTOR CURRENT, 100mA/div
C: SHDN, 5V/div
100 µ s/div
Power-Fail Input. When the voltage at PFI is below 614mV, PFO sinks current. PFI 2
Active-Low Shutdown. Connect SHDN to BATT for normal operation. SHDN 4
Open-Drain Power-Fail Output. PFO sinks current when PFI is below 614mV. PFO 3
Ground GND 6
Power Output and IC Power Input (bootstrapped). OUT is the feedback input for 3.3V operation. Connect
the filter capacitor close to OUT.
OUT 8
N-Channel MOSFET Switch Drain and P-Channel Synchronous-Rectifier Drain LX 7
Dual-Mode Feedback Input. Connect FB to GND for fixed-output operation (3.3V). Connect FB to a feed-
back-resistor network for adjustable output voltage operation (2V to 5.5V). FB regulates to 1.23V.
FB 5