Datasheet

MAX16932/MAX16933
2.2MHz, 36V, Dual Buck
with 20µA Quiescent Current
11Maxim Integrated
Pin Description (continued)
Detailed Description
The MAX16932/MAX16933 are automotive-rated dual-
output switching power supplies. These devices integrate
two synchronous step-down controllers and can provide
two independent controlled power rails as follows:
• A buck controller with a fixed 5V output voltage or an
adjustable 1V to 10V output voltage.
• A buck controller with a fixed 3.3V output voltage or
an adjustable 1V to 10V output voltage.
The two buck controllers can each provide up to 10A
output current and are independently controllable.
EN1 and EN2 enable the respective buck controllers.
Connect EN1 and EN2 directly to V
BAT
, or to power-
supply sequencing logic.
In skip mode, with no load and only buck 2 active, the
total supply current is reduced to 20µA (typ). When both
controllers are disabled, the total current drawn is further
reduced to 8µA (typ).
Fixed 5V Linear Regulator (BIAS)
The internal circuitry of the MAX16932/MAX16933
requires a 5V bias supply. An internal 5V linear regulator
(BIAS) generates this bias supply. Bypass BIAS with a
6.8µF or greater ceramic capacitor to guarantee stability
under the full-load condition.
The internal linear regulator can source up to 100mA
(150mA under EXTVCC switchover, see the EXTVCC
Switchover section). Use the following equation
to estimate the internal current requirements for the
MAX16932/MAX16933:
I
BIAS
= I
CC
+ f
SW
(Q
G_DH1
+ Q
G_DL1
+
Q
G_DH2
+ Q
G_DL2
) = 10mA to 50mA (typ)
where I
CC
is the internal supply current, 5mA (typ), f
SW
is the switching frequency, and Q
G_
is the MOSFET’s
total gate charge (specification limits at V
GS
= 5V). To
minimize the internal power dissipation, bypass BIAS to
an external 5V rail.
EXTVCC Switchover
The internal linear regulator can be bypassed by con-
necting an external supply (3V to 5.2V) or the output
of one of the buck converters to EXTVCC. BIAS inter-
nally switches to EXTVCC and the internal linear regulator
turns off. This configuration has several advantages:
• It reduces the internal power dissipation of the
MAX16932/MAX16933.
• The low-load efficiency improves as the internal sup-
ply current gets scaled down proportionally to the
duty cycle.
If V
EXTVCC
drops below V
TH,EXTVCC
= 3V (min), the
internal regulator enables and switches back to BIAS.
Undervoltage Lockout (UVLO)
The BIAS input undervoltage lockout (UVLO) circuitry
inhibits switching if the 5V bias supply (BIAS) is below
its 2.9V (typ) UVLO falling threshold. Once the 5V bias
supply (BIAS) rises above its UVLO rising threshold and
EN1 and EN2 enable the buck controllers, the controllers
start switching and the output voltages begin to ramp up
using soft-start.
PIN NAME DESCRIPTION
27 BST1
Boost Capacitor Connection for High-Side Gate Voltage of Buck 1. Connect a high-voltage diode
between BIAS and BST1. Connect a ceramic capacitor between BST1 and LX1. See the High-Side
Gate-Driver Supply (BST_) section.
28 DH1 High-Side Gate-Drive Output for Buck 1. DH1 output voltage swings from V
LX1
to V
BST1
.
— EP
Exposed Pad. Connect the exposed pad to ground. Connecting the exposed pad to ground does
not remove the requirement for proper ground connections to PGND1, PGND2, and AGND. The
exposed pad is attached with epoxy to the substrate of the die, making it an excellent path to
remove heat from the IC.