Datasheet

MAX8537/MAX8538/MAX8539
Dual-Synchronous Buck Controllers for Point-of-
Load, Tracking, and DDR Memory Power Supplies
_______________________________________________________________________________________ 7
Pin Description
PIN
NAME
(MAX8537/
MAX8539)
NAME
(MAX8538)
FUNCTION
1 BST2 BST2
Bootstrap Input to Power Internal High-Side Driver for Step-Down 2. Connect to an
external capacitor and diode according to Figure 1.
2 DH2 DH2 High-Side Gate-Driver Output for Step-Down 2. Swings from LX2 to BST2.
3 LX2 LX2
External Inductor Input for Step-Down 2. Connect to the switched side of the inductor.
LX2 serves as the lower supply-voltage rail for the DH2 high-side gate driver and the
current-limit circuitry.
4 ILIM2 ILIM2
Output Current-Limit Setting for Step-Down 2. Connect a resistor from ILIM2 to the
drain of the step-down 2 high-side MOSFET, or to the junction of the source of the
high-side MOSFET and the current-sense resistor to set the current-limit threshold.
See the Current-Limit Setting section.
5 POK1 POK1
Open-Drain Output. High impedance when step-down 1 is within 12% of its regulation
voltage. POK1 is pulled low in shutdown.
6 DL2 DL2 Low-Side Gate-Driver Output for Step-Down 2. Swings from PGND to VL.
7 POK2 POK2
Open-Drain Output. High impedance when step-down 2 is within 12% of its regulation
voltage. POK2 is pulled low in shutdown or if REFIN is undervoltage.
8 EN2 EN2 Enable Input for Step-Down 2 (also for VTTR for the MAX8537 and MAX8539)
9 EN1 EN1 Enable Input for Step-Down 1
10 FREQ FREQ
Frequency Adjust. Connect a resistor from this pin to ground to set the frequency. The
range of the FREQ resistor is 163kΩ, 20kΩ, and 100kΩ (corresponding to 1.4MHz,
1.0MHz, and 200kHz).
11 COMP2 COMP2 Compensation Pin for Step-Down 2. Connect to compensation networks.
12 FB2 FB2
Feedback Input for Step-Down 2 with V
REFIN
as the Threshold. User must have
impedance <40kΩ.
13 SS2 SS2 Soft-Start for Step-Down 2. Connect a capacitor to GND to set the soft-start time.
REFIN —
Reference Input for V
TT
and V
TTR
. Connect it to a resistor-divider from V
DDQ
. REFIN
common-mode voltage range is 0.5V to 2.5V. Current through the divider-resistors
must be ≥100µA.
14
— N.C. For the MAX8538, connect pin 14 to GND.
15 GND GND Analog Ground for Internal Circuitry
16 SS1 SS1 Soft-Start for Step-Down 1. Connect a capacitor to GND to set the soft-start time.
17 FB1 FB1
Feedback Input for Step-Down 1 with 0.8V Threshold. User must have impedance
<40kΩ.
18 COMP1 COMP1 Compensation Pin for Step-Down 1. Connect to compensation networks.
VTTR —
VTTR Output Capable of Sourcing and Sinking Up to 15mA. Always bypass with a 1µF
ceramic capacitor (or larger) to GND.
19
— GND Analog Ground for Internal Circuitry
20 AVL AVL
Analog VL Input Pin. Connect to VL through a 4.7Ω resistor. Bypass with a 0.1µF (or
larger) ceramic capacitor to GND.
21 V+ V+ Input Supply Voltage