MAX1845 Maxim, MAX1845 Datasheet - Page 9

• Manufacturer Part Number: MAX1845
• Description: Dual / High-Efficiency / Step-Down Controller with Accurate Current Limit
• Manufacturer: Maxim

QSOP
10
11
12
13
14
15
16
17
18
19
20
21
22
23
7
8
9
PIN
QFN
11
12
13
14
15
16
18
19
20
21
22
—
3
4
5
7
8
_______________________________________________________________________________________
PGOOD
NAME
OUT2
ILIM2
BST2
GND
ON1
ON2
OVP
UVP
DH2
REF
FB2
CS2
DL2
V
V
LX2
DD
CC
Controller with Accurate Current Limit
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.
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
U nd er vol tag e P r otecti on Thr eshol d . An und er vol tag e faul t occur s i f the vol tag e on FB1 or FB2 i s l ess
than the und er vol tag e tr i p thr eshol d ( 70% of nom i nal ) . C onnect U V P to V
p r otecti on. C onnect to GN D to d i sab l e und er vol tag e p r otecti on and cl ear the U V P l atch.
+2.0V Reference Voltage Output. Bypass to GND with 0.22µF (min) capacitor. Can supply 50µA
for external loads.
OU T1 ON /OFF C ontr ol Inp ut. C onnect to AGN D to tur n OU T1 off. C onnect to V
OU T2 ON /OFF C ontr ol Inp ut. C onnect to AGN D to tur n OU T2 off. C onnect to V
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
current-limit threshold.
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.
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.
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.
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.
High-Side Gate Driver Output for OUT2. Swings from LX2 to BST2.
Boost Flying Capacitor Connection for OUT2. Connect to an external capacitor and diode
according to the standard application circuit in Figure 1. See MOSFET Gate Drivers (DH_, DL_)
section.
Low-Side Gate-Driver Output for OUT2. DL2 swings from PGND to V
Supply Input for the DL Gate Drivers. Connect to system supply voltage, +4.5V to +5.5V. Bypass
to PGND with a low-ESR 4.7µF capacitor.
Analog Supply Input. Connect to system supply voltage, +4.5V to +5.5V, with a 20Ω series
resistor. Bypass to AGND with a 1µF capacitor.
Ground. Combined analog and power ground. Serves as negative input for CS_ amplifiers.
Dual, High-Efficiency, Step-Down
CC
to disable OVP and clear the OVP latch.
FUNCTION
Pin Description (continued)
C C
DD
CC
to enab l e und er vol tag e
.
to assert 50mV default
C C
C C
to tur n O U T1 on.
to tur n O U T2 on.
9