Rainbow Electronics MAX8737 - Manual (Page 9)

resistor network is calculated using the short-circuit
current (I
SHORT ), the maximum load current (I MAX ), cur-
rent-sense resistor (R CS ), the 10mV (±3mV) current-
limit threshold (V
ILIM
), and the external reference input
(REFIN_). See Figure 3:
1) Pick the R CS requirement for maximum short-cir-
cuit current:
2) Select R1 = 10
Ω and select R2 using the follow-
ing formula:
UVP Short-Circuit Protection
There are two levels of short-circuit UVP available in the
controller. When the current-limit protection is not used
(CS_= V
CC ), the output undervoltage timeout protection
is enabled, which protects the regulator against short
circuits. Output UVP timing depends on the magnitude
of the output voltage drop. To clear the UVP fault latch,
toggle the respective EN_ input, or cycle V
CC below its
UVLO threshold.
R
V V R
I R V
REFIN ILIM
MAX CS ILIM
2
1
=
+
−
( )
R V I
CS ILIM SHORT
= /
MAX8737
Dual, Low-Voltage Linear Regulator Controllers
with External MOSFETs
_______________________________________________________________________________________ 9
R6B
100k
Ω
POWER
GOOD 2
* A LOCAL 10 µF CERAMIC CAPACITOR WILL BE SUFFICIENT
FOR MOST APPLICATIONS. IF THE MAX8737 IS POWERED
FROM A HIGH-IMPEDANCE SOURCE, ADDITIONAL LOW-ESR
POLYMER CAPACITORS ARE RECOMMENDED ON THE INPUT.
N2
R3B
33
Ω
C2B
0.22
µF
C IN2
10 µF
C SYS2 *
100 µF
C OUT2
22 µF
1.05V
3A (MAX)
INPUT
1.25V TO 1.5V
ON
OFF
R2A
100k Ω
R1A
33.2k Ω
ON
OFF
R6A
100k Ω
POWER
GOOD 1
C
IN1
10 µF
C SYS1 *
100 µF
C OUT1
10 µF
1.5V
2A (MAX)
C1
1.0 µF
5V BIAS
SUPPLY
INPUT
1.8V TO 2.5V
R3A
27 Ω
C2A
0.1 µF
GND
REFIN1
EN1
OUT1
DRV1
PGOOD1
V CC
PGOOD2
DRV2
OUT2
EN2
MAX8737
NOTE: THE SYSTEM REFERENCE IS TYPICALLY
GENERATED BY THE STEP-DOWN CONVERTER
USED TO POWER THE DUAL LOW-VOLTAGE
LINEAR REGULATORS.
R4B
10
Ω
R5B
150
Ω
R1B
90k Ω
R2B
100k
Ω
SYSTEM REF (2.0V) SYSTEM REF (2.0V)
R4A
10 Ω
R5A
340 Ω
N1
REFIN2
R CS2
20m Ω
R CS1
20m Ω
CS1
CS2
N1/N2: Si 4922DY
Figure 1. Typical Operating Circuit with Current Limit