MAX5096AAUP+ Maxim Integrated Products, MAX5096AAUP+ Datasheet - Page 11

• Manufacturer Part Number: MAX5096AAUP+
• Description: IC DC-DC CONV BUCK 20TSSOP
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX5096AAUP+

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 2
• Voltage - Output: 3.3V, 1.24 ~ 11 V
• Current - Output: 600mA
• Frequency - Switching: 135kHz
• Voltage - Input: 5 ~ 40 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 20-TSSOP Exposed Pad, 20-eTSSOP, 20-HTSSOP
• Power - Output: 1.74W
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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.
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
Quiescent-Current Linear Regulator Mode
______________________________________________________________________________________
40V, 600mA Buck Converters with Low-
Detailed Description
Enable Input (EN)
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.
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 V
than 4V.
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 (C
achieved by the controlled ramping up of the error
amplifier reference input. At startup, after V
and the UVLO threshold is reached, the device enters
soft-start. During soft-start, 5µA is sourced into the
capacitor (C
causing the reference voltage to ramp up slowly. When
V
Set the soft-start time (t
where V
C
Pulling EN low quickly discharges the C
making it ready for the next soft-start period.
SS
SS
is in Farads.
reaches 1.237V, the output becomes fully active.
SS
is 1.237V, I
SS
) connected from SS to SGND (Figure 2)
t
SS
SS
SS
=
Internal Regulator (BP)/
V
) using following equation:
I
is 5µA, t
SS
SS
Undervoltage Lockout
×
C
SS
SS
SS
). The soft-start is
Soft-Start (SS)
is in seconds, and
SS
IN
capacitor,
is applied
IN
lower
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