LM25010SD/NOPB National Semiconductor, LM25010SD/NOPB Datasheet - Page 13

• Manufacturer Part Number: LM25010SD/NOPB
• Description: IC BUCK ADJ 1A 10LLP
• Manufacturer: National Semiconductor
• Type: Step-Down (Buck)r

Specifications of LM25010SD/NOPB

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 2.5 ~ 37 V
• Current - Output: 1A
• Frequency - Switching: 100kHz ~ 1MHz
• Voltage - Input: 6 ~ 42 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 10-LLP
• Primary Input Voltage: 42V
• No. Of Outputs: 1
• Output Voltage: 37V
• Output Current: 1A
• No. Of Pins: 10
• Operating Temperature Range: -40°C To +125°C
• Msl: MSL 1 - Unlimited
• Supply Voltage Range: 6V To 42V
• Rohs Compliant: Yes
• Filter Terminals: SMD
• For Use With: LM25010EVAL - BOARD EVALUATION LM25010
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: LM25010SD; LM25010SDTR

C3: The capacitor at the VCC pin provides noise filtering and
stability, prevents false triggering of the V
switch on/off transitions, and limits the peak voltage at V
when a high voltage with a short rise time is initially applied
at V
a good quality, low ESR, ceramic capacitor, physically close
to the IC pins.
C4: The recommended value for C4 is 0.022 µF. A high quality
ceramic capacitor with low ESR is recommended as C4 sup-
plies the surge current to charge the buck switch gate at each
turn-on. A low ESR also ensures a complete recharge during
each off-time.
C5: This capacitor suppresses transients and ringing due to
lead inductance at VIN. A low ESR, 0.1 µF ceramic chip ca-
pacitor is recommended, located physically close to the
LM25010.
C6: The capacitor at the SS pin determines the soft-start time,
i.e. the time for the reference voltage at the regulation com-
parator, and the output voltage, to reach their final value. The
capacitor value is determined from the following:
IN
. C3 should be no smaller than 0.47 µF, and should be
CC
UVLO at the buck
FIGURE 6. Example Circuit
CC
13
For a 5 ms softstart time, C6 calculates to 0.022 µF.
D1: A Schottky diode is recommended. Ultra-fast recovery
diodes are not recommended as the high speed transitions at
the SW pin may inadvertently affect the IC’s operation through
external or internal EMI. The diode should be rated for the
maximum V
peak current which occurs when current limit and maximum
ripple current are reached simultaneously (I
previously calculated to be 1.86A. The diode’s forward volt-
age drop affects efficiency due to the power dissipated during
the off-time. The average power dissipation in D1 is calculat-
ed from:
where I
FINAL CIRCUIT
The final circuit is shown in Figure 6, and its performance is
shown in Figures 7 & 8. Current limit measured approximately
1.3A.
O
is the load current, and D is the duty cycle.
IN
(40V), the maximum load current (1A), and the
P
D1
= V
F
x I
O
x (1 - D)
20172733
PK
in Figure 4),
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