Rainbow Electronics MAX1801 - Manual (Page 6)

MAX1801
Digital Camera Step-Up Slave
DC-DC Controller
6 _______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1 OSC
Oscillator Input. Connect OSC to OSC of the MAX1800 or MAX1802. The oscillator frequency must
be between 100kHz and 1MHz.
2 GND Ground
3 REF
1.25V Reference Input. Connect REF to REF of the MAX1800 or MAX1802. REF must be above 1V
for the controller to turn on. Bypass REF to GND with a 0.1µF or greater capacitor.
4 DCON
Maximum Duty-Cycle Control Input. Connect to REF or IN to set the default maximum duty cycle.
Connect a resistive voltage-divider from REF to DCON to set the maximum duty cycle between 40%
and 90%. Pull DCON below 0.35V to turn the controller off.
5 COMP
Controller Compensation. Output of transconductance error amplifier. Connect a series resistor and
capacitor to GND to compensate the control loop. See Compensation Design.
6 FB
Controller Feedback Input. Connect a feedback resistive voltage-divider from the output to FB to
set the output voltage. Regulation voltage is V
REF (1.25V).
7 IN
IC Supply Bias Input. Bypass IN to GND with a 0.1µF or greater ceramic capacitor. Supply range is
2.7V to 5.5V.
8 DL
External MOSFET Gate Drive Output. DL swings between IN and GND with typical 500mA drive
current. Connect DL to the gate of the external switching N-channel MOSFET.
STARTUP RESPONSE
MAX1801 toc10
V DCON
5V/div
V OUT
2V/div
I IN
0.5A/div
1ms/div
OV
OV
OA
LOAD TRANSIENT RESPONSE
MAX1801 toc11
V OUT
100mV/div
(AC-COUPLED)
400 µs/div
I LOAD
0.2A/div
V IN = =+2.4V, V OUT = +5V, f OSC = 500kHz
100mA
OA
500mA
Typical Operating Characteristics (continued)
(Circuit of Figure 1, T A = +25°C, unless otherwise noted.)