Pin description (continued) – Rainbow Electronics MAX1845 User Manual
Page 9
MAX1845
Dual, High-Efficiency, Step-Down
Controller with Accurate Current Limit
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9
Pin Description (continued)
PIN
NAME
FUNCTION
6
SKIP
Pulse-Skipping Control Input. Connect to V
CC
for low-noise forced-PWM mode. Connect to GND to
enable pulse-skipping operation.
7
PGOOD
Power-Good Open-Drain Output. PGOOD is low when either output voltage is off or is more than
10% above or below the normal regulation point.
8
OVP
Overvoltage Protection Threshold. An overvoltage fault occurs if the voltage on FB1 or FB2 is
greater than the programmed overvoltage trip threshold. Adjustment range is 1V (100%) to 1.8V
(180%). Connect OVP to GND to set the default overvoltage threshold of 114% of nominal. Connect
to V
CC
to disable OVP and clear the OVP latch.
9
UVP
Undervoltage Protection Threshold. An undervoltage fault occurs if the voltage on FB1 or FB2 is
less than the undervoltage trip threshold (70% of nominal). Connect UVP to V
CC
to enable
undervoltage protection. Connect to GND to disable undervoltage protection and clear the UVP
latch.
10
REF
2V Reference Voltage Output. Bypass to GND with 0.22µF (min) capacitor. Can supply 50µA for
external loads.
11
ON1
OUT1 ON/OFF Control Input. Connect to GND to turn OUT1 off. Connect to V
CC
to turn OUT1 on.
12
ON2
OUT2 ON/OFF Control Input. Connect to GND to turn OUT2 off. Connect to V
CC
to turn OUT2 on.
13
ILIM2
Current-Limit Threshold Adjustment for OUT2. The current-limit threshold at CS2 is 0.1 times the
voltage at ILIM2. Connect a resistor-divider network from REF to set the current-limit threshold
between 25mV and 250mV (with 0.25V to 2.5V at ILIM). Connect to V
CC
to assert 50mV default
current-limit threshold.
14
FB2
Feedback Input for OUT2. Connect to GND for 2.5V fixed output, or connect to a resistor-divider
network from OUT2 for an adjustable output between 1V and 5.5V.
15
OUT2
Output Voltage Connection for the OUT2 PWM. Connect directly to the junction of the external
inductor and output filter capacitors. OUT2 senses the output voltage to determine the on-time and
also serves as the feedback input in fixed-output modes.
16
CS2
Current-Sense Input for OUT2. CS2 is the input to the current-limiting circuitry for valley current
limiting. For lowest cost and highest efficiency, connect to LX2. For highest accuracy, use a sense
resistor. See the Current-Limit Circuit (ILIM_) section.
17
LX2
External Inductor Connection for OUT2. Connect to the switched side of the inductor. LX2 serves as
the internal lower supply voltage rail for the DH2 high-side gate driver.
18
DH2
High-Side Gate Driver Output for OUT2. Swings from LX2 to BST2.
19
BST2
Boost Flying Capacitor Connection for OUT2. Connect to an external capacitor and diode
according to the standard application circuit in Figure 1. See the MOSFET Gate Drivers (DH_, DL_)
section.
20
DL2
Low-Side Gate-Driver Output for OUT2. DL2 swings from GND to V
DD
.
21
V
DD
Supply Input for the DL Gate Drivers. Connect to system supply voltage, 4.5V to 5.5V. Bypass to
GND with a low-ESR 4.7µF capacitor.