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PDF MAX5097 Data sheet ( Hoja de datos )
| Número de pieza | MAX5097 | |
| Descripción | (MAX5096 / MAX5097) Buck Converters | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-0603; Rev 0; 7/06
40V, 600mA Buck Converters with Low-
Quiescent-Current Linear Regulator Mode
General Description
The MAX5096/MAX5097 easy-to-use, Dual Mode™,
DC-DC converters operate as LDO (low dropout) or
switch-mode buck converters. At a high output load,
the converters operate as high-efficiency pulse-width-
modulated (PWM) switch-mode converters and reduce
the power dissipation. The devices switch to a low-qui-
escent-current (IQ) LDO mode of operation at light load.
During the key-off condition, the system’s microcon-
troller drives the LDO/BUCK input on the fly and forces
the MAX5096/MAX5097 into LDO Mode, thereby reduc-
ing the quiescent current significantly.
In Buck Mode, the MAX5096/MAX5097 operate from a 5V
to 40V input voltage range and deliver up to 600mA of
load current with excellent load and line regulation. The
fixed-switching frequency versions of 135kHz and
330kHz are available. The MAX5096/MAX5097 DC-DC
internal oscillator can be synchronized to an external
clock. External compensation and a current-mode control
scheme make it easy to design with.
In LDO Mode, the MAX5096/MAX5097 operate from a
4V to 40V input voltage. The LDO Mode operation is
intended for a lower output load current of up to
100mA. The quiescent current at 100µA load in LDO
Mode is only 41µA (typ).
The MAX5096/MAX5097 feature an enable input that
shuts down the device, reducing the current consump-
tion to 6µA (typ). Additional features include a power-on
reset output with a capacitor-adjustable timeout period,
programmable soft-start, output tracking, output over-
load, short-circuit and thermal shutdown protections.
The MAX5096/MAX5097 operate over the -40°C to
+125°C automotive temperature range and are avail-
able in thermally enhanced 20-pin TSSOP or 16-pin
TQFN packages.
Applications
Features
♦ High-Efficiency Switcher Mode (Buck Mode) or
Low-Quiescent-Current Linear Regulator
(LDO Mode) Operation
♦ Wide Operating Input Voltage Range
+5V to +40V Buck Mode
+4V to +40V LDO Mode
♦ Fixed 3.3V or 5V and Adjustable (1.24V to 11V)
Output Voltage Versions
♦ 6µA (typ) Shutdown Current
♦ Fixed 135kHz or 330kHz Switching Frequency
♦ External Frequency Synchronization
♦ Programmable Soft-Start
♦ Integrated Microprocessor Reset (RESET) Circuit
with Programmable Timeout Period
♦ Thermal and Short-Circuit Protection
♦ -40°C to +125°C Automotive Temperature Range
♦ Thermally-Enhanced Package Dissipates
2.6W at TA = +70°C (16-Pin TQFN)
1.7W at TA = +70°C (20-Pin TSSOP)
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
PKG
CODE
MAX5096AATE+* -40°C to +125°C 16 TQFN-EP** T1655-2
MAX5096BATE+ -40°C to +125°C 16 TQFN-EP** T1655-2
MAX5096AAUP+* -40°C to +125°C 20 TSSOP-EP** U20E-4
MAX5096BAUP+* -40°C to +125°C 20 TSSOP-EP** U20E-4
MAX5097AATE+ -40°C to +125°C 16 TQFN-EP** T1655-2
MAX5097BATE+* -40°C to +125°C 16 TQFN-EP** T1655-2
MAX5097AAUP+* -40°C to +125°C 20 TSSOP-EP** U20E-4
MAX5097BAUP+* -40°C to +125°C 20 TSSOP-EP** U20E-4
*Future product—contact factory for availability.
+Denotes lead-free package.
**EP = Exposed pad.
Pin Configurations
Automotive
Industrial
Dual Mode is a trademark of Maxim Integrated Products, Inc.
TOP VIEW
16 15 14 13
+
PGND 1
SGND 2
RESET 3
MAX5096
MAX5097
BP 4
567 8
TQFN
TOP VIEW
+
IN 1
12 EN
11 OUT
10 ADJ
9 LDO/BUCK
IN 2
IN 3
PGND 4
SGND 5
RESET 6
BP 7
MAX5096
MAX5097
N.C. 8
SYNC 9
SS 10
TSSOP
20 LX
19 LX
18 N.C.
17 EN
16 OUT
15 ADJ
14 N.C.
13 LDO/BUCK
12 COMP
11 CT
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
www.DataSheet4U.com
40V, 600mA Buck Converters with Low-
Quiescent-Current Linear Regulator Mode
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +14V, IOUT = 1mA, CIN = 100µF, COUT = 22µF, L = 22µH, CBP = 1µF, VEN = +2.4V (Figure 2), SGND = PGND = 0V, TA = TJ =
-40°C to +125°C, unless otherwise noted. Typical values are at TA = TJ = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
EN Low-Voltage Threshold
EN Input Pulldown
RESET Voltage Threshold High
RESET Voltage Threshold Low
RESET Output-Low Voltage
RESET Output-High Leakage
Current
VENL
VRESET_H
VRESET_L
VRL
Regulator off
VEN = 2V, LDO/BUCK = 4V
VOUT rising
VOUT falling
ISINK = 1mA
IRH VRESET = 5V, VADJ = 1.5V
90
87
RESET Output Minimum Timeout
Period
VOUT to RESET Delay
Delay Comparator Threshold
VCT_TH
CCT = 0
VOUT falling 10mV/µs, CCT = 0
VCT rising
1.18
Delay Comparator Threshold
Hysteresis
CT Charge Current
CT Discharge Current
THERMAL SHUTDOWN
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
ICH
IDISCH
VCT = 1V
TJ(SHDN) Temperature rising
∆TJ(SHDN)
0.74
Note 1: Limits to -40°C are guaranteed by design.
Note 2: The continuous maximum output current from LDO is limited by package power dissipation.
TYP
0.5
92
90
25
6
1.2374
100
1
13.8
+165
20
MAX
0.4
94
92
0.2
1
1.29
1.20
UNITS
V
µA
% VOUT
% VOUT
V
µA
µs
µs
V
mV
µA
mA
°C
°C
_______________________________________________________________________________________ 5
5 Page 
www.DataSheet4U.com
40V, 600mA Buck Converters with Low-
Quiescent-Current Linear Regulator Mode
Detailed Description
The MAX5096/MAX5097 are easy-to-use, high-efficien-
cy, PWM current-mode, step-down switching convert-
ers in normal operation. The MAX5096/MAX5097 have
an internal high-side p-channel 0.9Ω switch and use a
low forward-drop freewheeling diode for rectification. In
Buck Mode, the p-channel switches at the 135kHz or
330kHz frequency. Buck Mode uses a current-mode
control architecture that offers excellent line-transient
response, easier frequency compensation, and cycle-
by-cycle current limiting. The buck converter is com-
pensated externally for a selected value/type of output
inductor and capacitor.
The internal p-channel switch acts as a pass element
when operating in the low-quiescent-current LDO
Mode.
The LDO Mode can be selected on the fly through the
LDO/BUCK input. During the key-off condition, the sys-
tem’s microcontroller drives the LDO/BUCK input high
and forces the MAX5096/MAX5097 into LDO Mode,
reducing the quiescent current to 1µA (typ). When in
LDO Mode, the device is capable of delivering up to
100mA, which may be limited by the device power dis-
sipation. The LDO and switcher share the same pass
element and the reference; however, the error ampli-
fiers are different with their own compensation
schemes.
The MAX5096/MAX5097 include an integrated micro-
processor reset circuit with an adjustable reset timeout
period. The internal reset circuit monitors the regulator
output voltage and asserts RESET low when the regula-
tor output falls below the reset threshold voltage. Other
features include an enable input, externally program-
mable soft-start, optimized current-limit protection in
both LDO and Buck Modes, and thermal shutdown.
Enable Input (EN)
EN is a logic-level enable input that turns the device on
or off. The logic-high and logic-low voltages for the EN
input are 1.4V and 0.4V, respectively. Drive EN high to
turn on the device, and drive it low to place the device
in shutdown. Leaving EN unconnected disables the
device since the EN is internally pulled low with a 0.5µA
current, however, a forced pulldown of EN improves the
noise immunity. The MAX5096/MAX5097 draw 6µA
(typ) of supply current when in shutdown. EN with-
stands up to +40V, allowing EN to be connected direct-
ly to IN for always-on operation. The converter may be
turned on and off while in both Buck and LDO Modes.
Each time the EN is toggled, the output rises with a pro-
grammed soft-start period.
Internal Regulator (BP)/
Undervoltage Lockout
The MAX5096/MAX5097 include an internal 4V auxiliary
regulator to power internal circuitry. Bypass the auxil-
iary regulator output (BP) to SGND with a 1µF ceramic
capacitor physically located close to the device. The
regulator is not intended to supply the external circuit
other than pulling up the LDO/BUCK input or RESET.
Do not load BP externally by more than 2mA. The regu-
lator output is regulated to 4V with 7% accuracy during
steady state. During turn-on, the BP voltage stabilizes
after 250µs with a 1µF capacitor at BP. Drive EN high to
turn on the internal regulator. The internal UVLO with
hysteresis ensures stable operation, resulting in the
monotonic rise of the output voltage. The UVLO circuit
monitors the output of the regulator. The rising UVLO
threshold is internally set to 3.65V (BP rising) with a
185mV hysteresis (BP falling). The 3.65V UVLO at the
no-load BP output guarantees operation at VIN lower
than 4V.
Soft-Start (SS)
Soft-start provides for the monotonic, glitch-free turn-on
of the converter. Soft-start limits the input inrush current
which may cause a glitch, especially if the source
impedance is high. The soft-start period required also
depends on the output capacitance and the closed-
loop bandwidth of converter. The soft-start period for
the MAX5096/MAX5097 is externally programmable
using a single capacitor (CSS). The soft-start is
achieved by the controlled ramping up of the error
amplifier reference input. At startup, after VIN is applied
and the UVLO threshold is reached, the device enters
soft-start. During soft-start, 5µA is sourced into the
capacitor (CSS) connected from SS to SGND (Figure 2)
causing the reference voltage to ramp up slowly. When
VSS reaches 1.237V, the output becomes fully active.
Set the soft-start time (tSS) using following equation:
tSS
=
VSS
ISS
× CSS
where VSS is 1.237V, ISS is 5µA, tSS is in seconds, and
CSS is in Farads.
Pulling EN low quickly discharges the CSS capacitor,
making it ready for the next soft-start period.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet MAX5097.PDF ] | |
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