Rainbow Electronics MAX1759 - Manual (Page 5)

MAX1759
Buck/Boost Regulating
Charge Pump in µMAX
_______________________________________________________________________________________ 5
Typical Operating Characteristics (continued)
(Circuit of Figure 1, C
IN
= 10µF, C
X
= 0.33µF, C
OUT
= 10µF, V
OUT
= 3.3V, V
IN
= 2.5V, T
A
= +25°C, unless otherwise noted.)
NAME FUNCTION
1 POK
Open-Drain Power-OK Output. POK is high impedance when output voltage is in regulation. POK sinks current
when V
FB falls below 1.1V. Connect a 10k Ω to 1MΩ pull-up resistor from POK to V
OUT for a logic signal.
Ground POK or leave unconnected if not used. POK is high impedance in shutdown.
2 SHDN
Shutdown Input. Drive high for normal operation; drive low for shutdown mode. OUT is high impedance in
shutdown.
PIN
3, 4 IN
Input Supply. Connect both pins together and bypass to GND with a ceramic capacitor (see Capacitor
Selection section).
5 GND Ground. Connect GND to PGND with a short trace.
9 OUT Power Output. Bypass to GND with an output filter capacitor.
8 CXP Positive Terminal of the Charge-Pump Transfer Capacitor
7 CXN Negative Terminal of the Charge-Pump Transfer Capacitor
6 PGND Power Ground. Charge-pump current flows through this pin.
10 FB
Dual-Mode Feedback. Connect FB to GND for 3.3V output. Connect to an external resistor divider to adjust
the output voltage from 2.5V to 5.5V.
Pin Description
1
2
-4.2V
-2.5V
100 µs/div
LINE-TRANSIENT RESPONSE
MAX1759 toc10
CH1: V OUT , 20mV/div, AC-COUPLED
CH2: V IN , 1V/div, AC-COUPLED
R LOAD = 33 Ω
1
2
3
4
500 µs/div
TURN-ON/OFF RESPONSE
(V IN = 4.2V)
MAX1759 toc11
CH1: V OUT ,1V/div
CH2: I IN , 200mA/div
CH3: V POK , 5V/div
CH4: V SHDN , 5V/div
R LOAD = 33 Ω
V IN = 4.2V
1
2
3
4
500 µs/div
TURN-ON/OFF RESPONSE
(V IN = 2.5V)
MAX1759 toc12
CH1: V OUT ,1V/div
CH2: I IN , 200mA/div
CH3: V POK , 5V/div
CH4: V SHDN , 5V/div
R LOAD = 33 Ω
V IN = 2.5V