LM5005MH/NOPB National Semiconductor, LM5005MH/NOPB Datasheet - Page 10

• Manufacturer Part Number: LM5005MH/NOPB
• Description: IC BUCK SYNC ADJ 2.5A 20TSSOP
• Manufacturer: National Semiconductor
• Type: Step-Down (Buck)r

Specifications of LM5005MH/NOPB

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.23 ~ 70 V
• Current - Output: 2.5A
• Frequency - Switching: 500kHz
• Voltage - Input: 7 ~ 75 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 20-TSSOP Exposed Pad, 20-eTSSOP, 20-HTSSOP
• Power - Output: 3.5W
• Dc To Dc Converter Type: Inverting/Step Down
• Pin Count: 20
• Input Voltage: 75V
• Output Voltage: 1.225 to 70V
• Switching Freq: 50 TO 500KHz
• Output Current: 2.5A
• Efficiency: 90%
• Package Type: TSSOP EP
• Output Type: Adjustable
• Switching Regulator: Yes
• Mounting: Surface Mount
• Input Voltage (min): 7V
• Operating Temp Range: -40C to 125C
• Operating Temperature Classification: Automotive
• For Use With: LM5005EVAL - BOARD EVALUATION LM5005
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *LM5005MH; *LM5005MH/NOPB; LM5005MH

www.national.com
Shutdown / Standby
The LM5005 contains a dual level Shutdown (SD) circuit.
When the SD pin voltage is below 0.7V, the regulator is in a
low current shutdown mode. When the SD pin voltage is
greater than 0.7V but less than 1.225V, the regulator is in
standby mode. In standby mode the Vcc regulator is active
but the output switch is disabled. When the SD pin voltage
exceeds 1.225V, the output switch is enabled and normal op-
eration begins. An internal 5µA pull-up current source config-
ures the regulator to be fully operational if the SD pin is left
open.
An external set-point voltage divider from Vin to GND can be
used to set the operational input range of the regulator. The
divider must be designed such that the voltage at the SD pin
will be greater than 1.225V when Vin is in the desired oper-
ating range. The internal 5µA pull-up current source must be
included in calculations of the external set-point divider. Hys-
teresis of 0.1V is included for both the shutdown and standby
thresholds. The voltage at the SD pin should never exceed
7V. When using an external set-point divider, it may be nec-
essary to clamp the SD pin to limit its voltage at high input
voltage conditions.
Oscillator and Sync Capability
The LM5005 oscillator frequency is set by a single external
resistor connected between the RT pin and the AGND pin.
The R
connected directly to the pins of the IC (RT and AGND).To
set a desired oscillator frequency (F), the necessary value for
the R
The SYNC pin can be used to synchronize the internal oscil-
lator to an external clock. The external clock must be of
higher frequency than the free-running frequency set by the
R
recommended interface from the external clock to the SYNC
pin. The clock pulse duration should be greater than 15 ns.
T
resistor. A clock circuit with an open drain output is the
T
T
resistor can be calculated from the following equation:
resistor should be located very close to the device and
FIGURE 3. Sync from External Clock
20161905
10
Multiple LM5005 devices can be synchronized together sim-
ply by connecting the SYNC pins together. In this configura-
tion all of the devices will be synchronized to the highest
frequency device. The diagram in Figure 5 illustrates the
SYNC input/output features of the LM5005. The internal os-
cillator circuit drives the SYNC pin with a strong pull-down /
weak pull-up inverter. When the SYNC pin is pulled low either
by the internal oscillator or an external clock, the ramp cycle
of the oscillator is terminated and a new oscillator cycle be-
gins. Thus, if the SYNC pins of several LM5005 IC’s are
connected together, the IC with the highest internal clock fre-
quency will pull the connected SYNC pins low first and termi-
nate the oscillator ramp cycles of the other IC’s. The LM5005
with the highest programmed clock frequency will serve as
the master and control the switching frequency of the all the
devices with lower oscillator frequency.
FIGURE 4. Sync from Multiple Devices
20161906