Datasheet

MAX1776
Diode Selection
The current in the external diode (D1 in Figure 1)
changes abruptly from zero to its peak value each time
the LX switch turns off. To avoid excessive losses, the
diode must have a fast turn-on time and a low forward
voltage.
Make sure that the diodes peak current rating exceeds
the peak current limit set by the current limit, and that
its breakdown voltage exceeds V
IN
. Use Schottky
diodes when possible.
MAX1776 Stability
Instability is frequently caused by excessive noise on
OUT, FB, or GND due to poor layout or improper com-
ponent selection. Instability typically manifests itself as
motorboating, which is characterized by grouped
switching pulses with large gaps and excessive low-
frequency output ripple during no-load or light-load
conditions.
PC Board Layout and Grounding
High switching frequencies and large peak currents
make PC board layout an important part of the design.
Poor layout introduces switching noise into the feed-
back path, resulting in jitter, instability, or degraded
performance. High-power traces, highlighted in the
24V, 600mA Internal Switch, 100% Duty Cycle,
Step-Down Converter
12 ______________________________________________________________________________________
Table 3. Recommended Components
CIRCUIT
INPUT
VOLTAGE
(V)
MAXIMUM
LOAD
CURRENT
(mA)
I
LX(PEAK)
CURRENT
(A)
INDUCTOR CAPACITOR
1 10 to 24 600 1.20
10µH, 1.56A, 70m
Toko D75F 646FY-100M,
10µH, 1.70A, 48m
Sumida CDRH6D28-100NC,
or 10µH, 1.63A, 55m
Toko D75C 646CY-100M 0.055
100µF, 6.3V
Sanyo POSCAP 6TPC100M
2 10 to 24 300 0.60
22µH, 1.17A, 120m
Toko D75F 646FY-220M,
22µH, 1.09A, 115m
Toko D75C 646CY-220M,
or 22µH, 1.20A, 95m
Sumida CDRH6D28-220NC
47µF, 6.3V
Sanyo POSCAP 6TPA47M
3 10 to 24 150 0.30
47µH, 0.54A, 440m
Sumida CDRH5D18-470
22µF, 6.3V, 1210 case
Taiyo Youden JMK325BJ226MM
4 10 to 24 75 0.15
100µH, 0.29A, 766m
Sumida CDRH4D28-101
10µF, 6.3V, X7R, 1206 case
Taiyo Youden JMK316BJ106ML
5 5 to 15 600 1.20
5.4µH, 1.6A, 56m
Sumida CDRH5D18-5R4
100µF, 6.3V
Sanyo POSCAP 6TPC100m
6 5 to 15 300 0.60
10µH, 1.04A, 80m
Toko D73LC 817CY-100M
47µF, 6.3V
Sanyo POSCAP 6TPA47M
7 5 to 15 150 0.30
22µH, 0.41A, 294m
Sumida CDRH4D18-220
22µF, 6.3V, 1210 case
Taiyo Youden JMK325BJ226MM
8 5 to 15 75 0.15
47µH, 0.33A, 230m
Coilcraft DS1608C-473
10µF, 6.3V, X7R, 1206 case
Taiyo Youden JMK316BJ106ML