Rainbow Electronics MAX17101 - Manual (Page 14)

MAX17101
Dual Quick-PWM, Step-Down Controller
with Low-Power LDO, RTC Regulator
14 ______________________________________________________________________________________
Pin Description (continued)
PIN NAME FUNCTION
14 ON1 Enable Input for SMPS1. Drive ON1 high to enable SMPS1. Drive ON1 low to shut down SMPS1.
15 DH1 High-Side Gate-Driver Output for SMPS1. DH1 swings from LX1 to BST1.
16 LX1
Inductor Connection for SMPS1. Connect LX1 to the switched side of the inductor. LX1 is the lower supply
rail for the DH1 high-side gate driver.
17 BST1
Boost Flying-Capacitor Connection for SMPS1. Connect to an external capacitor as shown in Figure 1. An
optional resistor in series with BST1 allows the DH1 turn-on current to be adjusted.
18 DL1 Low-Side Gate-Driver Output for SMPS1. DL1 swings from PGND to V DD.
19 V DD
Supply-Voltage Input for the DL_ Gate Drivers. Connect to a 5V supply. Also connect to the drain of the
BST diode switch.
20 SECFB
Secondary Feedback Input. The secondary feedback input forces the SMPS1 output into ultrasonic mode
when the SECFB voltage drops below its 2V threshold voltage. This forces DL1 and DH1 to switch,
allowing the system to refresh an external low-power charge pump being driven by DL1 (see Figure 1 for
the Standard Application Circuit—Main Supply). Connect SECFB to V
CC (the 5V bias supply) to disable
secondary feedback.
21 AGND Analog Ground. Connect backside exposed pad to AGND.
22 PGND Power Ground
23 DL2 Low-Side Gate-Driver Output for SMPS2. DL2 swings from PGND to V DD.
24 BST2
Boost Flying-Capacitor Connection for SMPS2. Connect to an external capacitor as shown in Figure 1. An
optional resistor in series with BST2 allows the DH2 turn-on current to be adjusted.
25 LX2
Inductor Connection for SMPS2. Connect LX2 to the switched side of the inductor. LX2 is the lower supply
rail for the DH2 high-side gate driver.
26 DH2 High-Side Gate-Driver Output for SMPS2. DH2 swings from LX2 to BST2.
27 ON2 Enable Input for SMPS2. Drive ON2 high to enable SMPS2. Drive ON2 low to shut down SMPS2.
28 PGOOD2
Open-Drain Power-Good Output for SMPS2. PGOOD2 is low when the output voltage is more than 150mV
(typ) below the REFIN2 voltage or more than 16% below the preset voltage, during soft-start, in shutdown,
and when the fault latch has been tripped. After the soft-start circuit has terminated, PGOOD2 becomes
high impedance if the output is in regulation. PGOOD2 is blanked—forced high-impedance state—when a
dynamic REFIN transition is detected.
29 SKIP
Pulse-Skipping Control Input. This three-level input determines the operating mode for the switching
regulators:
High (V
CC or 3.3V) = forced-PWM operation
Open/REF (2V) = ultrasonic mode
GND = pulse-skipping mode
30 OUT2
Output Voltage-Sense Input for SMPS2. OUT2 is an input to the Quick-PWM on-time one-shot timer. OUT2
also serves as the feedback input for the preset 3.3V (REFIN2 = V
CC ) and 1.05V (REFIN2 = RTC).
31 ILIM2
Valley Current-Limit Adjustment for SMPS2. The GND - LX2 current-limit threshold is 1/10 the voltage
present on ILIM2 over a 0.2V to 2V range. An internal 5μA current source allows this voltage to be set with
a single resistor between ILIM2 and analog ground.
32 REFIN2
External Reference Input for SMPS2. REFIN2 sets the feedback-regulation voltage (V OUT2 = V REFIN2 ).
Connect REFIN2 to RTC for fixed 1.05V operation. Connect REFIN2 to V CC for fixed 3.3V operation.
— EP Exposed Pad. Connect the backside exposed pad to AGND.