Rainbow Electronics MAX662A - Manual (Page 5)

Layout Considerations
Layout is critical, due to the MAX662A’s high oscillator
frequency. Good layout ensures stability and helps
maintain the output voltage under heavy loads. For best
performance, use very short connections to the capaci-
tors. The order of importance is: C4, C5, C1, C2.
Flash EEPROM Applications
The circuit of Figure 3a is a +12V ±5% 30mA flash
EEPROM programming power supply. A microproces-
sor controls the programming voltage via the SHDN
pin. When SHDN is low, the output voltage (which is
connected to the flash memory V
PP supply-voltage pin)
rises to +12V to facilitate programming the flash memo-
ry. When SHDN is high, the output voltage is connected
to V
IN through an internal 1k Ω resistor.
Paralleling Devices
Two MAX662As can be placed in parallel to increase
output drive capability. The V
CC , V OUT , and GND pins
can be paralleled, reducing pin count. Use a single
bypass capacitor and a single output filter capacitor
with twice the capacitance value if the two devices can
be placed close to each other. If the MAX662As cannot
be placed close together, use separate bypass and
output capacitors. The amount of output ripple
observed will determine whether single input bypass
and output filter capacitors can be used. Under certain
conditions, one device may supply the total output cur-
rent. Therefore, regardless of the number of devices in
parallel, the maximum continuous current must not
exceed 50mA.
12V and 20V Dual-Output Power Supply
Using the charge-pump voltage-doubler circuit of
Figure 4, the MAX662A can produce a +20V supply
from a single +5V supply. Figure 5 shows the current
capability of the +20V supply.
MAX662A
+12V, 30mA Flash Memory
Programming Supply
_______________________________________________________________________________________ 5
Table 1. Capacitor Suppliers
MAX662A
*C1
1.0
µ F
2
1
8
7
C2-
C2+
V CC
V OUT
PROGRAMMING
CONTROL
DIRECT FROM
µ P
*C2
1.0 µ F
V IN
4.75V TO 5.5V
*C4
22 µ F
V OUT
+12V ±5%
AT 30mA
*C5
22 µ F
C1+
C1-
SHDN
GND
3
4
5
6
*SPRAGUE 595D SERIES OR EQUIVALENT
MAX662A
C1
0.22
µ F
2
1
8
7
C2-
C2+
V CC
V OUT
PROGRAMMING
CONTROL
DIRECT FROM
µ P
C2
0.22 µ F
V IN
4.75V TO 5.5V
C4
4.7 µ F V OUT
+12V ±5%
AT 30mA C5
4.7 µ F
C1+
C1-
SHDN
GND
3
4
5
6
Figure 3a. Flash EEPROM Programming Power Supply for
Commercial Temperature Range Applications
Figure 3b. Flash EEPROM Programming Power Supply for
Extended and/or Military Temperature Range Applications
Supplier Phone Number Fax Number Capacitor Capacitor Type*
GRM42-6Z5U224M50 0.22µF Ceramic (SM)
Murata Erie (814) 237-1431 (814) 238-0490
RPE123Z5U105M50V 1.0µF Ceramic (TH)
595D475X9016A7 4.7µF Tantalum (SM)
Sprague Electric
(603) 224-1961
(207) 324-4140 (603) 224-1430
(207) 324-7223
595D105X9016A7 1.0µF Tantalum (SM)
*Note: (SM) denotes surface-mount component, (TH) denotes through-hole component.