MAX1540A Datasheet, PDF (18/49 Pages) Maxim Integrated Products – Dual Step-Down Controllers with Saturation Protection, Dynamic Output, and Linear Regulator

Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
PIN
MAX1540A MAX1541
13
17
14
18
15
19
16
20
17
21
18
22
19
23
—
24
—
25
20
26
—
27
21
28
22
29
23
30
Pin Description (continued)
NAME
FUNCTION
PGOOD2
DH2
LX2
BST2
GND
DL2
V+
LDOIN
V_DD
LDOOUT
FBLDO
DL1
LDOON
BST1
Open-Drain Power-Good Output. PGOOD2 is low when the output voltage is more
than 10% (typ) above or below the normal regulation point, during soft-start, and in
shutdown. After the soft-start circuit has terminated, PGOOD2 becomes high
impedance if the output is in regulation.
High-Side Gate-Driver Output for Controller 2. DH2 swings from LX2 to BST2.
Inductor Connection for Controller 2. Connect to the switched side of the inductor.
LX2 serves as the lower supply rail for the DH2 high-side gate driver.
Boost Flying-Capacitor Connection for Controller 2. Connect to an external capacitor
and diode as shown in Figure 8. An optional resistor in series with BST2 allows the
DH2 pullup current to be adjusted.
Analog and Power Ground. Connect backside pad to GND.
Low-Side Gate-Driver Output for Controller 2. DL2 swings from GND to LDOOUT
(MAX1540A) or GND to V_DD (MAX1541).
Battery Voltage Input. The controller uses V+ to set the on-time one-shot timing. The
DH on-time is inversely proportional to input voltage over a range of 2V to 28V. For
the MAX1540A, V+ also serves as the linear-regulator input supply.
Internal Linear-Regulator Input Supply. Power LDOIN from a 4.5V to 28V voltage
source. Bypass LDOIN to GND with a 4.7µF or greater capacitor. For the MAX1540A,
LDOIN is internally connected to V+. For the MAX1541, LDOIN must be connected to
V_DD when LDO is not used.
MAX1541 Supply Voltage Input for the DL_ Gate Driver. Connect to the system
supply voltage (+4.5V to +5.5V). Bypass V_DD to power ground with a 1µF or greater
ceramic capacitor. For the MAX1540A, LDOOUT supplies the DL_ gate drivers
(V_DD = LDOOUT).
Linear Regulator Output. Bypass LDOOUT with a 1µF or greater capacitor per 5mA of
load (internal and external), with a minimum of 4.7µF. For the MAX1540A, LDOOUT
powers the DL_ gate drivers (V_DD internally connected to LDOOUT).
Feedback Input for the Linear Regulator. Connect to GND for a fixed 5V output. For
an adjustable output (1.25V to V_LDOIN - 0.6V), connect FBLDO to a resistive voltage-
divider from LDOOUT to analog ground (GND). The FBLDO regulation voltage is
+1.25V. For the MAX1540A, FBLDO is internally connected to GND for a fixed 5V
output.
Low-Side Gate-Driver Output for Controller 1. DL1 swings from GND to LDOOUT
(MAX1540A) or GND to V_DD (MAX1541).
Linear-Regulator Enable Input. For automatic startup, connect to V+ or LDOIN
(MAX1541). Connect to GND to shut down the linear regulator.
Boost Flying-Capacitor Connection for Controller 1. Connect to an external capacitor
and diode as shown in Figure 8. An optional resistor in series with BST1 allows the
DH1 pullup current to be adjusted.
18 ______________________________________________________________________________________